Using NSNotificationCenter passing an object or value?
I am trying to pass along a custom UIButton's tag down to another class I am
writing.
In my custom view which contains the custom UIButton, I have this code *(A):
*
-(void) buttonClicked:(id)sender
{
[[NSNotificationCenter defaultCenter]
postNotificationName:@ButtonClicked
object:sender];
In a class which manages these custom views, I have this code *(B):*
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
mydata = [[NSArray alloc] init];
menuItems = [[NSMutableArray alloc] initWithCapacity:40];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(buttonClicked) name:@ButtonClicked object:nil];
}
return self;
}
-(void) buttonClicked {
//This works, but I need to know the tag
NSLog(@clicked);
}
Now, obviously in that I have object set to nil. How can I set this up? I
could change object to nil and use userInfo:someNSDictionary in the
customview which contains the UIButton... but I run into the same problem
in *(B). * I really haven't seen much in Google in regards to userInfo and
looking for some help on it. I understand some of how it works, not sure how
to set that *addObserver* part up properly.
Sorry for the noob question.
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Re: Using NSNotificationCenter passing an object or value?
On Aug 3, 2010, at 12:34, Eric E. Dolecki wrote:
-(void) buttonClicked:(id)sender
{
[[NSNotificationCenter defaultCenter]
postNotificationName:@ButtonClicked
object:sender];
In a class which manages these custom views, I have this code *(B):*
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
mydata = [[NSArray alloc] init];
menuItems = [[NSMutableArray alloc] initWithCapacity:40];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(buttonClicked) name:@ButtonClicked object:nil];
}
return self;
}
-(void) buttonClicked {
//This works, but I need to know the tag
NSLog(@clicked);
}
Now, obviously in that I have object set to nil. How can I set this up? I
could change object to nil and use userInfo:someNSDictionary in the
customview which contains the UIButton... but I run into the same problem
in *(B). * I really haven't seen much in Google in regards to userInfo and
looking for some help on it. I understand some of how it works, not sure how
to set that *addObserver* part up properly.
You *really* need to read the documentation. Your second buttonClicked
method prototype is wrong -- it takes a NSNotification object as a parameter.
If you had coded that properly, you would have a way of getting the
notification's userInfo. (Or, to get the object and ask it for its tag. Or
whatever.)
Your first buttonClicked method (why give them the same name?) can use
'postNotificationName:object:userInfo:' if you really need to pass userInfo.
(Again, you don't need to use userInfo if you just want the button's tag.)
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Re: Using NSNotificationCenter passing an object or value?
On Aug 3, 2010, at 13:00, Eric E. Dolecki wrote:
WHen you say it takes an NSNotification object as a parameter, you mean to
say that it's missing, correct?
Yes, as in:
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
mydata = [[NSArray alloc] init];
menuItems = [[NSMutableArray alloc] initWithCapacity:40];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(buttonClicked:) name:@ButtonClicked object:nil];
// note the colon in the selector now
}
return self;
}
-(void) buttonClicked: (NSNotification*) notification {
UIButton* button = notification.object;
NSUInteger tag = button.tag;
}
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Re: Using NSNotificationCenter passing an object or value?
Many thanks. I didn't know object could be nil yet still pass it along when
populated
On Aug 3, 2010, at 4:15 PM, Quincey Morris quinceymor...@earthlink.net wrote:
On Aug 3, 2010, at 13:00, Eric E. Dolecki wrote:
WHen you say it takes an NSNotification object as a parameter, you mean to
say that it's missing, correct?
Yes, as in:
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
mydata = [[NSArray alloc] init];
menuItems = [[NSMutableArray alloc] initWithCapacity:40];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(buttonClicked:) name:@ButtonClicked object:nil];
// note the colon in the selector now
}
return self;
}
-(void) buttonClicked: (NSNotification*) notification {
UIButton* button = notification.object;
NSUInteger tag = button.tag;
}
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Re: Using NSNotificationCenter passing an object or value?
On Aug 3, 2010, at 13:50, eric dolecki GMail wrote: Many thanks. I didn't know object could be nil yet still pass it along when populated I *knew* you were going to say exactly that. :) Specifying nil for the 'object:' parameter just means (and I quote from the NSNotificationCenter reference) the notification center doesn’t use a notification’s sender to decide whether to deliver it to the observer. All notifications still have a sender, available as the 'object' property of the notification object. If the parameter had been named something like 'objectFilter:' instead, you wouldn't have been confused. As it is, reading the documentation would have cleared up the apparent ambiguity, which is why I keep harping on READING THE DOCUMENTATION. ___ 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
Re: Using NSNotificationCenter passing an object or value?
On 04/08/2010, at 5:34 AM, Eric E. Dolecki wrote:
-(void) buttonClicked:(id)sender
{
[[NSNotificationCenter defaultCenter]
postNotificationName:@ButtonClicked
object:sender];
Notwithstanding Quincey's excellent advice, this approach is poor use of MVC.
The Button is a view. The thing that responds to the button is the controller.
At that point, the button should have done its job and is no longer a relevant
object in the design. WHAT DOES THE BUTTON DO? This is the question the
controller needs to be asking itself, and messaging the data model
appropriately, not just punting the button object somewhere else for somebody
else to make that call (clue: if ever you send a notification and the object
parameter is not 'self', you need to asking hard questions about why that is).
The controller is not doing its job here, and you've made an unnecessary link
between view and model.
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
mydata = [[NSArray alloc] init];
menuItems = [[NSMutableArray alloc] initWithCapacity:40];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(buttonClicked) name:@ButtonClicked object:nil];
}
return self;
}
This also suggests you've embodied your model (mydata) in a view. It's one
reason you're resorting to using notifications to perform basic messaging -
nobody is really clear about their correct role here.
If you can separate your design into clearly defined model, view and controller
layers, things will be far easier. Notifications have a useful part to play but
you're abusing them here in order to band-aid a muddled design.
General documentation about MVC should be a vital read at this point.
--Graham
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Re: Using NSNotificationCenter passing an object or value?
You're right... mydata is indeed in a view.
I have a subclassed UIView to serve as my component ui - and it creates
instances of subclassed UIViews (containers) which in turn contain
subclassed UIButton items. Since I was being quickly lazy in prototyping, I
didn't include a view controller for any of these things... my main UIView
was the engine for the whole thing. When a user clicked on an item, the
button press was dispatched from the container view class back to the main
container class - so that layout code, etc. could happen.
Eric
On Tue, Aug 3, 2010 at 9:37 PM, Graham Cox graham@bigpond.com wrote:
On 04/08/2010, at 5:34 AM, Eric E. Dolecki wrote:
-(void) buttonClicked:(id)sender
{
[[NSNotificationCenter defaultCenter]
postNotificationName:@ButtonClicked
object:sender];
Notwithstanding Quincey's excellent advice, this approach is poor use of
MVC.
The Button is a view. The thing that responds to the button is the
controller. At that point, the button should have done its job and is no
longer a relevant object in the design. WHAT DOES THE BUTTON DO? This is the
question the controller needs to be asking itself, and messaging the data
model appropriately, not just punting the button object somewhere else for
somebody else to make that call (clue: if ever you send a notification and
the object parameter is not 'self', you need to asking hard questions about
why that is). The controller is not doing its job here, and you've made an
unnecessary link between view and model.
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
mydata = [[NSArray alloc] init];
menuItems = [[NSMutableArray alloc] initWithCapacity:40];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(buttonClicked) name:@ButtonClicked object:nil];
}
return self;
}
This also suggests you've embodied your model (mydata) in a view. It's one
reason you're resorting to using notifications to perform basic messaging -
nobody is really clear about their correct role here.
If you can separate your design into clearly defined model, view and
controller layers, things will be far easier. Notifications have a useful
part to play but you're abusing them here in order to band-aid a muddled
design.
General documentation about MVC should be a vital read at this point.
--Graham
--
http://ericd.net
Interactive design and development
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