Re: Question about matrix of possibilities
On Oct 16, 2013, at 12:48 PM, Eric E. Dolecki edole...@gmail.com wrote: I've been asked to make a tableview with 8 rows. Each row has a UISwitch. Based on a combination of switch values, the result would be a different image displayed to the right of the table (this is for iPad). How would I best go about covering all of those combinations? When one switch changes I'll check it's on/off state and then run some evaluation method based on the values for all of the switches. How do I do that without getting too ugly about it? There are a bunch of ways to handle this—for example, you can assign each switch a power-of-two value based on their index in the tableview's data source, and then add the ones that are on together; this will give you a separate number for each possible combination, which you can then use as the name of the corresponding image (0.png, 1.png … 255.png). ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
I seem to have a loose end though -- when I examine the UIWebView's scrollView property, it initially has a non-nil delegate. I don't know if I should interpose as delegate and after taking my snapshot, call the original delegate, or only set myself as a delegate instead of the original. I'm afraid that posing as the delegate but still maintaining the original delegate, may imply that I need to implement the WHOLE delegate protocol, just to pass on all delegate calls to the original delegate. Any ideas? Nothing other than trying it out and see what happens… even if you have to interpose yourself between the scrollview and its original delegate, UIScrollViewDelegate only needs a dozen or so methods anyway. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
On 2013-04-22, at 3:26 AM, Motti Shneor su...@bezeqint.net wrote: Hello everyone. I asked this several times before, but no one gave any hint -- I'd like to know if anyone here has any clue, at least where to search for an answer. I need to observe the visible contents of a UIWebView dIsplayed in my iOS application. Each time the visible contents changes, I need to capture the contents as image, and transmit it to our server. A bit like screen-sharing on the Mac, but not for the whole screen contents, just a single view. My apologies: another possibility would be to poll at regular intervals, but, instead of capturing the entire view, use Javascript to pull its HTML tree, compare it with the previous version, and perform a new capture if you detect changes. It's still brutal, but, in this case, you'd be comparing two strings, which is probably less effort than comparing two images and can be easily delegated to a secondary thread. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
On 2013-04-22, at 9:04 AM, Motti Shneor su...@bezeqint.net wrote: To be very precise --- I'd like to know how to be notified about ANY UIView visual change. It somehow seems very obvious to me that such delegate call must exist. Maybe I'm overlooking something very basic here. I think I had completely misunderstood what you wanted to do! I think what you want to do is interpose yourself as the delegate of the UIWebView's UIScrollView instance (accessible through the -scrollview property); that lets you track changes in scroll position, zoom level, etc. Is that what you meant? —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: How to implement readonly property
Looking at the docs, dispatch_once takes care of the synchronization for you:
https://developer.apple.com/library/mac/ipad/#documentation/Performance/Reference/GCD_libdispatch_Ref/Reference/reference.html
It should therefore be thread safe to use without any additional
synchronization code.
Sent from my New iPad. I blame all typos on the Fruit Company. May have been
dictated.
On 2012-11-12, at 7:56 AM, Gerriet M. Denkmann gerr...@mdenkmann.de wrote:
I have a property:
@property (readonly) NSDictionary *someDictionary;
This property should be computed on demand, and should be accessible by
several threads.
My current implementation is:
- (NSDictionary *)someDictionary;
{
static NSDictionary *someDictionary;
static dispatch_once_t justOnce;
dispatch_once( justOnce, ^
{
// create a temp dictionary (might take some time)
someDictionary = temp;
}
);
return someDictionary;
}
The first thread which needs someDictionary will trigger its creation. Ok.
But what happens when another thread wants to access someDictionary while it
is still being created? I guess it will receive just nil.
This would be not correct; it really should wait until the dictionary is
ready.
How to achieve this? Use a lock? Use @synchronize?
10.8.2 with Arc.
Gerriet.
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Re: How to implement readonly property
This is completely the wrong way to implement a property. The static
variable will be shared between all instances. Here's how you should be
doing a lazy loaded var:
@implementation MyClass
{
NSDictionary *_someDictionary
}
- (NSDictionary *)someDictionary
{
static dispatch_once_t justOnce;
dispatch_once(justOnce, ^
{
someDictionary = [[NSDictionary alloc] initWithObjectsAndKeys: ……
nil];
});
return someDictionary;
}
I don't think this does what you think it does; my understanding is that
dispatch_once will execute only once for the lifetime of an app, so the code
you posted will only run once for the first object that requires is, and then
never run again, resulting in _dictionary being Nil in all other instances.
I understood the OP's request as wanting to implement a singleton, which, based
on your reading, may not be the case. dispatch_once will be fine for a
singleton, but if you need a thread-safe, lazily-instantiated read-only
property, maybe something like this will do the trick:
@implementation MyClass {
NSDictionary *_someDictionary
}
- (NSDictionary *) someDictionary {
@synchronized(self) {
if (!_someDictionary) {
_someDictionary = [[NSDictionary alloc] initWith… ]
}
}
return _someDictionary;
}
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Re: ARC issue
I wonder if the problem might be that data is an autoreleased object, which
automatically gets dealloc'ed at the end of the autorelease pool (as explained
in the docs). Have you tried replacing
*error = data
with
*error = [data copy]
and seeing what happens?
On 2012-11-07, at 8:05 AM, Andreas Grosam agro...@onlinehome.de wrote:
NSDictionary* fetchUser(NSNumber* ID, NSError** error)
{
id user = nil;
//@autoreleasepool // crashes when @autoreleasepool is enabled
{
id data = ...; // response body of a HTTP Response (NSData) or NSError
object, never nil.
if ([data isKindOfClass:[NSData class]]) {
user = [NSJSONSerialization JSONObjectWithData:data
options:0
error:error];
}
else if (error) {
*error = data;
}
} // autoreleasepool
return user;
}
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Re: KVG generic enough?
On 2012-07-18, at 9:08 AM, William Squires wsqui...@satx.rr.com wrote: Okay, after reading some of the documentation on KVC coding, I understand (I think) that the point is to allow me to specify a property of an object with an NSString, then set/get that property value using KVC (i.e. valueForKey: or setValue:forKey:). But it seems like the fact that there's no way to specify (or grab) the value of the property in a generic-enough manner would be a problem - anyone using it would still have to know the data type of the property they want to access, and thus they might as well just use the accessors. I can see this would work if ObjC had a generic data type (like the 'variant' data type in VB/REALbasic), but AFAIK, ObjC doesn't have such, and valueForKey: returns an id, right? How can I determine what I get back? (i.e. what does the id pointer point to? an NSString? an NSNumber? NSDecimalNumber? NSData? another NSObject subclass?) id *is* ObjC's “variant” type. You can determine the type of the underlying data by first determining its class (e.g.: [obj isKindOfClass:[NSString class]]), and then going from there. Scalar or composite values are wrapped in the appropriate classes—e.g.: NSNumber for numeric values and NSValue for generic data. The whole system is really quite flexible, particularly when you consider that ObjC, unlike so many other languages, doesn't choke on Nil values. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
[ANN]: Beeblex - Free IAP verification service for iOS
Howdy! My company launched a (completely free) verification service for in-app purchases on iOS, designed for apps that do not have a server-side component. The service, called Beeblex, requires only minimal set up—we provide a simple SDK, which we have also open-sourced, and we perform the validation against Apple's IAP services through our own services. It is really free—we don't even collect any information we don't absolutely need to run it. You can find it here: http://www.beeblex.com/ Thanks! Marco Tabini 416-630-6202 x.666 ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: How to implement an object whose properties are really dictionary entries.
On 2012-07-11, at 10:03 AM, Dave DeLong davedel...@me.com wrote: It sounds like the OP is looking for a model object that uses an NSMutableDictionary as the backing store for its properties, as opposed to individual ivars. You can do this. You declare all your properties, and you declare a single NSMutableDictionary ivar. All of the properties should be implemented as @dynamic in the .m file. Since the properties are dynamic, the compiler will not generate implementations for them. You'll have to do that yourself at runtime. Fortunately, if you know what you're doing, that's not too hard. You'll have to override +resolveInstanceMethod: to figure out what the user is trying to do: get or set. You'll use the selector passed in to derive the key under which you're storing the data in the dictionary. With this information, you construct a block of the appropriate signature, capturing whatever information you need, and turn it into an IMP using imp_implementationWithBlock(). You can then add that method to the class using class_addMethod(). Another way would be to override the invocation forwarding mechanism (-forwardInvocation: and -methodSignatureForSelector:) to funnel all the messages through a single getter/setter; this would (possibly) mean that less code is generated at runtime, perhaps at the expense of some added complexity and performance degradation. I think, however, that the best solution here is to just adopt a newer compiler; recent versions of LLVM are capable of automatically synthesizing properties[1], and provide support for both literals and boxed expressions[2], which make initializing and using both NSArray and NSDictionary much closer to what the OP was looking for. —Mt. [1]: “Objective-C Autosynthesis of Properties” in http://clang.llvm.org/docs/LanguageExtensions.html#objc_lambdas [2]: http://clang.llvm.org/docs/ObjectiveCLiterals.html ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Dynamic modification of text search results
Does anyone have any good suggestions as to how to update my search results when the underlying source text changes? Do I have to listen for all changes from the underlying text objects and try to adapt, or is there a better pattern for doing this? Xcode does this nicely: no matter what changes you make in the editor, the search results seem to be updated on the fly. Couple of random suggestions: * If you're using NSAttributedString, you can mark your search results by assigning custom attributes to specific ranges of text; as the text changes, those attributes will stick around and you can later find them using the attribute retrieval methods (I believe that's what Xcode does). * As an alternative, a more naïve approach could be to simply repeat the search every time you detect the text changing, but depending on the size of your text files, that could eat up a lot of CPU cycles, and is just inelegant. I'm sure there are other possibilities, too, but these two are the first ones that come to mind. HTH, —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Dynamic modification of text search results
On 2012-07-04, at 1:01 PM, Martin Hewitson martin.hewit...@aei.mpg.de wrote: On 4, Jul, 2012, at 03:22 PM, Marco Tabini wrote: Does anyone have any good suggestions as to how to update my search results when the underlying source text changes? Do I have to listen for all changes from the underlying text objects and try to adapt, or is there a better pattern for doing this? Xcode does this nicely: no matter what changes you make in the editor, the search results seem to be updated on the fly. Couple of random suggestions: * If you're using NSAttributedString, you can mark your search results by assigning custom attributes to specific ranges of text; as the text changes, those attributes will stick around and you can later find them using the attribute retrieval methods (I believe that's what Xcode does). Just a follow up on this. I guess I would have to clear all text attachements of a particular class from all files at the start of a search, right? Otherwise the attachments will build up over time. I don't actually save attributed text to disk (these are plain text files) but even so. Does that make sense? I wondering how computationally expensive this will turn out to be. That's correct. My experience has been that NSMutableAttributedString's performance is pretty good, but YMMV depending on platform, complexity, and size of the data. In my case, I wrote a Markdown syntax highlighter that could handily manage multi-MB text files on a run-of-the-mill Macbook. I guess there's no way to tell until you try :-) —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Using Instruments to profile UITableView drawing
I wonder if someone could point me to the right way to profile poorly-performing custom-drawn UITableView cells. I've come across this problem several times, and usually manage to figure out how to solve it, but my process is not very scientific—there's far too much trial and error involved, and I wonder whether there isn't a known way to pinpoint exactly which part of the code causes a table to stutter using Instruments. I've tried Googling for the problem, but it seems to me that the vast majority of people giving suggestions are focusing on known techniques to make table cells perform, rather than trying to understand where an already-implemented table is going astray. Thanks! —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: iOS App - crash when clearing a UITableDetailView
Hi David— On 2012-04-03, at 6:33 AM, David Delmonte wrote: After changing a setting and removing a subview from a UITableDetailView, I get crashes when I accidentally swipe the detail view. Can you reduce this down to a code sample? There is no such thing as a UITableDetailView (I used to work for the Department of Pedantry ;-)), which suggests that this is a custom class you wrote. Perhaps you're removing something from your table view in a way that ends up causing the crash. For example, are you using a table view with static cells designed in a storyboard? If so, removing rows at runtime is going to be very tricky and, unless you take a lot of precautions, you are likely to get crashes. But, as I said, that's just a guess and we may be able to help you a bit more if we can see some code. Cheers, —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Passing data through a segue
On 2012-04-02, at 7:15 AM, Rick Mann wrote: Thanks for the quick response. I think I'm okay with sending stuff through the sender parameter, although I do agree it's a bit ugly. Problem is, my didSelectRowAtIndexPath isn't getting called... :-( The delegate is set correctly, so I'm assuming iOS doesn't call it in the presence of segues? It IS calling prepareSegue... Have you tried to override -prepareForSegue:sender: and use -[UITableView indexPathForSelectedRow] to retrieve the selected row? That does the trick for me. Incidentally, you'll probably find that -willSelectRowAtIndexPath does get called. Cheers, —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Question about UIImage, scaling, and UIGraphicsBeginImageContextWithOptions
Hi Ray— But this seems kludgy and it's using programmer's knowledge, so to speak. I watched WWDC2010 session 134 Optimize your iPhone App for the Retina Display again, searched stackoverflow etc. but I can't find a more elegant solution. What would be a more thorough approach? Maybe it's staring me in the face but I don't see it... UIImage does not represent the actual bits of an image, but, rather, provides the logical metadata wrapper of an underlying image object (in this case, a CGImage) to store information like scale and orientation. When you save to a file format that supports metadata, like JPEG, some of the metadata is stored there, while other is derived from the file name. So, for example, if you were to save a PNG file to disk with an @2x suffix, upon loading it with -imageNamed: UIImage would automatically know to set up the resulting object as a 2x scale image. When the filename convention is not available, that metadata needs to be saved somewhere—in your case, you derive it from the file size, which, as you mention, is not very portable. I would have saved the scale in a separate Core Object property, or avoided saving the image in a data store to start with, and used a file cache, in which case UIImage is a bit more self-reliant. In practice, I would want to look at more significant problems with your approach in a real-life deployment scenario. For example, what happens when your Core Data store is transferred from a non-Retina device to a Retina device? This could happen in a variety of scenarios: the user could start using your app on a non-Retina device (say, an iPad 2), then buy a new Retina device (a New iPad), back up the old one and restore on the new one. Now, your images are cached at 1x scale, but the device wants to run at 2x. Or, perhaps, you may, at some point, want to sync your data store using iCloud, causing some images to be generated on Retina devices, and some others at 1x scale. Conversely, if your data is only ever used for caching purposes and is stored in the Caches directory, then this is a non-problem. Since the images are both going to be generated and used on the very same device, you don't need to derive the scale of the image from its size—you can just use the scale of your main screen both when creating and recreating your UIImage objects. Then again, if you move your images to individual files and save them with the appropriate @2x suffix, this whole problem goes away altogether—so, perhaps, that may be a better solution. Cheers, —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
UIBezierPath stroke oddity
In an attempt to figure out how well gesture recognizers work, I've built a
very simple app that uses a UIPanGestureRecognizer and using them to construct
a UIBezierPath that I then stroke, but I am getting strange artifacts on the
resulting drawing operation (see http://cl.ly/0N2R411O1t1x3w2N3Q3q for example).
The code I use is fairly simple; I start with a call to -moveToPoint:, followed
by a bunch of -addLineToPoint: calls. Other than the fact that I am recording
the points using touch, there is nothing unusual in the code (that I can see):
- (void) pannedRefineEdge:(UIPanGestureRecognizer *) recognizer {
switch (recognizer.state) {
case UIGestureRecognizerStateBegan:
_path = [[UIBezierPath alloc] init];
[_path moveToPoint:[recognizer locationInView:self.backgroundView]];
break;
case UIGestureRecognizerStateChanged:
[_path addLineToPoint:[recognizer
locationInView:self.backgroundView]];
break;
case UIGestureRecognizerStateEnded:
// This calls a function that sets up an image drawing context and
then:
_path.lineCapStyle = kCGLineCapRound;
_path.lineJoinStyle = kCGLineJoinRound;
_path.lineWidth = 10.0;
[[UIColor colorWithRed:1.0 green:0.6 blue:0.6 alpha:1.0] setStroke];
[_path stroke];
break;
default:
break;
}
}
Any ideas what could be causing the problem?
Thanks,
Marco
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Re: How to get Mac codesign certificate?
On 2012-03-17, at 9:18 AM, Gerriet M. Denkmann wrote: But I want to codesign my OS X apps. So how do I get the necessary certificate? You need to buy it from a certificate authority, like Thawte or Verisign (or one of the myriad resellers) and they will all be happy to sell you one at prices that range from around $80 to around $500/yr. Alternatively, you can get a certificate from Apple as part of the OS X Developer Program, which will cost you the extra $100/yr but also includes beta access to OS X system software. If you have control over the environment on which you deploy your software, you can also create a self-signed certificate and, essentially, be your own authority by adding yourself as a valid root CA on all the machines on which you software will run. If you don't, you can use a self-signed certificate to ensure the integrity of your code, but not your identity. Apple has a bunch of good resources on this topic[1], which are worth a read if you want more info. HTH, —Mt. [1]: https://developer.apple.com/library/mac/#documentation/Security/Conceptual/CodeSigningGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40005929-CH1-SW1 ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: How to get Mac codesign certificate?
Can you not just use a free provider, like http://www.startssl.com/? I'm not an expert, but I think the free cert they provide cannot be used for code signing. One other alternative may be the Developer ID initiative that Apple has announced as part of OS X 10.8 Mountain Lion, but I can't figure out if that's still under NDA and don't want to incur the wrath of the mods :-) —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Why so many public properties all up in my grizzle?
That time has passed now, so you can now completely specify IBOutlets (and IBActions) in your implementation file and hide the details from the outside world. If you want properties, you can use a class extension like so to add them: Sorry to hijack this conversation, but I've been meaning to ask: Where is this documented? I stumbled on this feature (and the ability to declare ivars directly in the .m file), but I didn't see it explained it anywhere. I'm sure I'm just not looking in the right place, but I can't find it anywhere. Cheers, Marco ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: The current preferred method for fetching HTTP URLs for IOS
I've been reading (and trying out) a few approaches on HTTP communication using GCD to do a dispatch_sync or dispatch_async to a dispatch queue or using an NSURLRequest. Which of these is the preferred method for ingesting strings from HTTP URLs on iOS? Are there any plusses to one over the other? FWIW, my view is that it depends on what your requirements are. For a simple request, you can go with an [NSString stringWithContentsOfURL] wrapped in a call to dispatch_async to avoid blocking the main thread. If you require a more sophisticated level of control over the transaction, NSURLRequest is obviously a better choice. Personally, I almost always find this to be the case, if only because I can cancel a request if necessary. As for running an NSURLRequest on a thread other than the main thread, I've found very little use for it unless you need the download to continue after your app has been pushed into the background. Otherwise, it just introduces an additional level of complexity that I prefer to avoid if I can :-) —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: JSON validator for Xcode
BOOL isTurnableToJSON = [NSJSONSerialization isValidJSONObject: responseData]; NSLog(@Is legit for JSON: %d, isTurnableToJSON ); NSLog(@Is legit for JSON: %@, isTurnableToJSON ? @YES : @NO); // this is how we handle a bool :/ Are you sure that you are using isTurnableToJSON the way it's meant to be? My understanding is that its job is to check whether an existing Objective-C object (like an NSDictionary) can be safely converted to JSON, and not to check whether a string contains valid JSON. From this code, it looks as though you are either trying to validate an NSData object—which you can't, because there's no way to represent NSData in JSON—or a string that has been converted into an NSData object. In either case, you will always get BOOL, and the method is functioning as expected. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Finding object array index when iterating through array
I have an array and I am iterating through it using this technique:
for (id object in array) {
// do something with object
}
Is there way to obtain the object's current array index position or do I
have to add a counter?
[array indexOfObject:object] should do the trick, though, if you need to do it
at every iteration, keeping a counter may be better.
—Mt.
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Re: Accessing array in thread safe way
On 2012-03-06, at 2:51 PM, Jan E. Schotsman wrote: Hello, I have an array of progress values (number objects) for subprojects, from which I calculate the overall progress . The array is an atomic property of the project class. Is it safe to access this array from multiple threads, using methods like objectAtIndex and replaceObjectAtIndex? NSMutableArray is not (as far as I know) thread-safe while being mutated[1]. That said, it doesn't mean that you can't use the array in a multi-threaded environment: Just make sure that writes are all synchronized, and that enumerations only happen on immutable copies. HTH, —Mt. [1]: https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Multithreading/ThreadSafetySummary/ThreadSafetySummary.html ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Question on handling very large images
The problem is that if you do this in a naive way, with a single huge pixmap, you will have poor locality of reference. Once you get to 1024 RGBA pixels across, every scan-line will occupy its own memory page. So any operation that crosses lots of scan lines but only uses a small fraction of each one (like drawing a vertical line) may involve a lot of paging. The usual workaround to that is to instead break the image up into rectangular tiles, and store each as a separate pixmap. That way most localized graphics operations will only involve a fraction of the total number of tiles. (You can see Photoshop do this, if you run a slow operation or if it’s had to page part of the image out to disk.) I think this will also help with the GPU, because CoreGraphics likes to copy pixmaps to GPU memory so they can be rendered and manipulated faster. Thanks for the helpful tips! That's pretty much how I ended up organizing things, and it seems to work OK so far. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Question on handling very large images
Hi Everyone, I find myself in the situation of having to manipulate and display a few very large images in an app running on iOS (potentially in the tens of megapixels at 24 bits/pixel), and I am trying to figure out what the correct pattern for doing so is. I've Googled for solutions, but there seems to be a large amount of variance in the kinds of answers that I've found, so I wanted to ask for some advice before heading out on a wild goose chase. Can anyone share their view or point me in the direction of some good ideas? My first instinct is to use a memory-mapped file (e.g.: using NSMutableData) to hold the data while I work on it, but I worry that it will be very slow and that I'm missing a much simpler solution. All help greatly appreciated! Cheers, Marco ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Suggestions for forcing NSSlider to some values, without tickmarks
On 2012-03-01, at 4:18 PM, Sean McBride wrote: Hi all, I have a continuous linear NSSlider who's range is -180 to 180 degrees. I don't want tick marks because any value is acceptable. However, the value zero is important, and I need for the user to be able to get to exactly 0.0 (0.1 or whatever is no good). How would you suggest accomplishing this? Off the top of my head, I would simply fence the NSSlider to zero when its value is within a given range from that value: on a change event, if (say) -5 ≤ 0 ≤ 5, you can force the value to zero. You can then allow for finer tuning of the value by implementing the fencing only when the user moves the slides with the mouse, and instead allow any value when the user uses the arrow keys to reposition the slider's knob. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: ARC in Snow Leopard?
On 2012-02-11, at 6:25 PM, William Squires wrote: is ARC a Lion-only feature or will an ARC-compiled app work on 10.6.8 assuming no other Lion features are used? According to Apple, ARC-compiled apps run on SL, but they must be compiled on Lion, because the SL version of Xcode doesn't include the 10.7 SDK. More info in the Transitioning to ARC guide. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: How do you run an app on the device with Instruments?
On 2012-01-30, at 5:10 PM, G S wrote: So... no one knows how to launch an app on the device with Instruments? Launch Instruments Select an iOS instrument Click “All Processes,” select your device from the list Click “All Processes” again, choose “Attach to Progress” is the app is already running, or “Choose Target” if it isn't Is that what you meant, or did I misunderstand your q? —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: How to get the dispatch queue for the current thread's runloop?
On 2012-01-27, at 2:14 PM, Jens Alfke wrote:
I'm really used to using -performSelector:withObject:afterDelay: to make
something happen later. But I'd much rather use a block than a target/action.
I can't find any API for this, however. Am I missing something? What I want
is basically like
PerformBlockAfterDelay(^{ …code here…}, 5.0);
It looks like I should just call dispatch_async, but I'm unsure which
dispatch queue to use. dispatch_get_main_queue only works for the main
thread. Can I use dispatch_get_current_queue? I'm unsure of what this does
when called on a background thread. The API docs say If the call is made
from any other thread, this function returns the default concurrent queue …
is that a queue associated with the thread's runloop, that's guaranteed to
execute tasks on that thread?
I just use a little category on NSObject that I think I pulled from
somewhere—but I can't remember where from:
#pragma mark -
#pragma mark Delayed block execution
- (void) performBlock:(void (^)(void)) block afterDelay:(NSTimeInterval) delay {
block = [block copy];
[self performSelector:@selector(fireBlockAfterDelay:)
withObject:block
afterDelay:delay];
}
- (void)fireBlockAfterDelay:(void (^)(void))block {
block();
}
This is pretty old code (it relies on ARC, though), so there might be a better
way to do it these days.
—Mt.
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Re: ARC and blocks
On 2012-01-26, at 3:51 PM, Jan E. Schotsman wrote:
Hello,
This code is given in the Transitioning to ARC Release Notes as an example
of accomodating blocks in an ARC environment:
__block MyViewController *myController = [[MyViewController alloc] init…];
// ...
myController.completionHandler = ^(NSInteger result) {
[myController dismissViewControllerAnimated:YES completion:nil];
myController = nil;
};
Supposedly this avoids a retain cycle. But where is the cycle? At least two
objects are needed for a cycle. What is the second one?
ARC has changed the behaviour of __block [1] so that it forces a retain of the
value (previously, it forced a variable to behave like a weak property). This
(as I understand it) is necessary because otherwise the value would be released
at the end of the current method, which is obviously not what you want. Note
that, even if you don't specify myController as __block, the variable will
still be declared with an implicit __strong attribute.
The key is that, by declaring it as __block, you give your block the option to
alter its contents. At the end of the block, you simply force it to Nil, which
implicitly releases it, thus breaking the retain cycle. Pretty neat, eh?
HTH,
—Mt.
[1]: See the CLANG docs, section 7.5.
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Re: ARC and blocks
On 2012-01-26, at 6:09 PM, Jeff Kelley wrote: Without ARC, you would use __block to prevent the block from retaining the object and causing the retain cycle. With ARC, however, the object is retained when you put it into the variable, so to avoid a retain cycle, you have to declare it like so: __unsafe_unretained __block MyViewController *myController = … It looks awful, yes, but without the first piece we were having extreme memory leaks. Maybe I'm reading this wrong, but I think this might be a bit too unsafe. If you declare something as __unsafe_unretained, ARC won't try to track the variable through its lifetime, so if for some reason that variable is deallocated and then your block gets called, your app will crash. The OP's code feels a bit safer to me: it retains the variable strongly, then Nils it at the end of the block to force a release. There's no retain cycle or memory leak, and the __block variable is guaranteed to stick around until your block is done with it. —Mt. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Angle of touch point from center of view?
On 2012-01-05, at 1:49 PM, Eric E. Dolecki wrote:
I'd like to calculate the angle from a center point of a view to a touch
point.
0º behind top of screen, 180º being bottom of screen.
Calculating from touchesMoved.
I think you can just retrieve the arctangent between the x axis and the vector
formed by the origin and location of the touch (reversing the y coordinate).
For example:
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint center = self.center;
CGPoint location = [[touches anyObject] locationInView:self];
CGPoint vectorOfInterest = CGPointMake(location.x - center.x, center.y -
location.y);
NSLog(@Vector: %@, Angle: %.2fº,
NSStringFromCGPoint(vectorOfInterest),
atan2(vectorOfInterest.x, vectorOfInterest.y) * 57.29);
}
The resulting angle will be [0, π) clockwise starting from the top, and [-π, 0)
from the bottom (or something like that—my trig is horribly rusty).
HTH,
—Mt.___
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Re: Saving PNG files from NSImage
Hi Martin— On 2011-08-29, at 8:18 AM, Martin Linklater wrote: Can anyone point me in the right direction as to how to save my NSImage to a PNG file ? Or some documentation which actually describes how to convert the NSCGImageSnapshotRep into something I can save out ? I've spent a few hours on this now and I can't believe there isn't an easy solution I'm missing. Take a look here: http://stackoverflow.com/questions/4438802/nscgimagesnapshotrep-how-get-bitmapdata HTH, —Mt. -- Phone: +1-416-630-6202 x.666 Twitter: @mtabini ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
