Re: Sending a Selector to another Class.
On 22/10/2009, at 3:52 PM, Joshua Garnham wrote: Ah, I see. so I need to send it to an instance of the class not the class it self. How would I do that? With respect, please understand that your questions are akin to this: Q. How do I start the car? A. You turn the key. Q. How do I drive? A. ummm You need to learn the basics of Objective-C, it is very clear that you do not understand even the simplest concepts. To directly answer your question, you allocate and initialize an instance of your class using [[YourClass alloc] init], or using a convenience class method or other designated initializer. However, this information is unlikely to help you until you invest some time in learning Objective-C. I personally recommend reading this book: http://www.amazon.com/Programming-Objective-C-2-0-Stephen-Kochan/dp/0321566157 It's all laid down here though: http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/index.html -- Rob Keniger ___ 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: Sending a Selector to another Class.
With all due respect, but by 'directly answering the question' you are doing the OP and all those reading this list a dis-service. You are just rewarding his lazyness. The OP has already been told to bone up on Obj-C basics, and he's obviously completely ignored this advice, the reason being that people continue to answer his silly questions. He will learn how to find his own answers if forced to do so, and will become a much better coder as a result. It's much better for him and for all the rest of us, if you would please refrain from 'directly answering the question in these circumstances. paulm On 22/10/2009, at 7:12 PM, Rob Keniger wrote: On 22/10/2009, at 3:52 PM, Joshua Garnham wrote: Ah, I see. so I need to send it to an instance of the class not the class it self. How would I do that? With respect, please understand that your questions are akin to this: Q. How do I start the car? A. You turn the key. Q. How do I drive? A. ummm You need to learn the basics of Objective-C, it is very clear that you do not understand even the simplest concepts. To directly answer your question, you allocate and initialize an instance of your class using [[YourClass alloc] init], or using a convenience class method or other designated initializer. However, this information is unlikely to help you until you invest some time in learning Objective-C. I personally recommend reading this book: http://www.amazon.com/Programming-Objective-C-2-0-Stephen-Kochan/dp/ 0321566157 It's all laid down here though: http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ ObjectiveC/index.html -- Rob Keniger ___ 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/list%40no-tek.com This email sent to l...@no-tek.com ___ 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: Sending a Selector to another Class.
Jens, thanks for clearing up the thing about the selector defining a message (method plus parameters) rather than a method and thus not being tied to a class. On Thu, Oct 22, 2009 at 1:21 AM, Jens Alfke j...@mooseyard.com wrote: On Oct 21, 2009, at 9:43 AM, Jim Kang wrote: That selector is a unique index that points to a method of a specific class. No, that's not true of Objective-C (although it is of C++ method-pointers.) A selector is, basically, just a unique string: it defines a *message*, not a method, to use the old Smalltalk OOP terminology. However, a selector is not a string. I was just listening to this podcast with Mike Ash, and he discusses this around the 9:23 mark or so: http://podcast.mobileorchard.com/episode-23-mike-ash-on-the-objective-c-runtime-objects-and-the-runtime-message-sending-and-no-such-method/ He explains that comparing strings is too slow for the runtime to use for finding messages and so it uses integers to represent the messages and calls them selectors. Any class that implements a method with that name uses the same selector for it, regardless of inheritance. To be specific, if I create two unrelated classes A and B, each of which implements a -foo method, the selector @selector(foo) is used for both. This is really good to know. ___ 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: Sending a Selector to another Class.
On Oct 22, 2009, at 5:54 AM, Jim Kang wrote: However, a selector is not a string. I was just listening to this podcast with Mike Ash, and he discusses this around the 9:23 mark or so: http://podcast.mobileorchard.com/episode-23-mike-ash-on-the-objective-c-runtime-objects-and-the-runtime-message-sending-and-no-such-method/ He explains that comparing strings is too slow for the runtime to use for finding messages and so it uses integers to represent the messages and calls them selectors. Selectors are strings, but it is an implementation detail. The runtime uniques the strings such that there is only ever one instance of, say, the drawRect: selector floating about. Thus, the runtime can use pointer comparison to determine selector equality. It is an implementation detail though. One that is exceedingly unlikely to ever change but, still, an implementation detail. Use the Objective-C runtime API if you want to do selector comparison. sel_isEqual(), IIRC. b.bum ___ 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: Sending a Selector to another Class.
On Oct 22, 2009, at 5:54 AM, Jim Kang wrote: However, a selector is not a string. I was just listening to this podcast with Mike Ash, and he discusses this around the 9:23 mark or so: http://podcast.mobileorchard.com/episode-23-mike-ash-on-the-objective-c-runtime-objects-and-the-runtime-message-sending-and-no-such-method/ He explains that comparing strings is too slow for the runtime to use for finding messages and so it uses integers to represent the messages and calls them selectors. This statement is true; however those integers happen to be the memory addresses of unique instances of the strings*. This makes it very efficient for the runtime to convert a selector to an NSString, and vice versa, and also helps with debugging (in gdb you can just type print (char*)sel to inspect a selector.) —Jens * C strings, not NSStrings.___ 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: Sending a Selector to another Class.
On Oct 22, 2009, at 9:01 AM, Jens Alfke j...@mooseyard.com wrote: This statement is true; however those integers happen to be the memory addresses of unique instances of the strings*. This makes it very efficient for the runtime to convert a selector to an NSString, and vice versa, and also helps with debugging (in gdb you can just type print (char*)sel to inspect a selector.) Don't forget NSStringFromSelector, which I find is usually more convenient and doesn't rely on implementation details. Invoke it in GDB by casting its return value to id: po (id)NSStringFromSelector(_cmd) (Although I have noticed that gdb is much better about inferring when it can expect an object return value from a function/method call). --Kyle Sluder ___ 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: Sending a Selector to another Class.
On Oct 22, 2009, at 10:53 AM, Bill Bumgarner wrote: Selectors are strings, but it is an implementation detail. The runtime uniques the strings such that there is only ever one instance of, say, the drawRect: selector floating about. Thus, the runtime can use pointer comparison to determine selector equality. It is an implementation detail though. One that is exceedingly unlikely to ever change but, still, an implementation detail. Use the Objective-C runtime API if you want to do selector comparison. sel_isEqual(), IIRC. b.bum http://twitter.com/gparker/status/2400099786 Ignore bbum. We hereby promise never to break == for SEL. (But SEL is not char*. We will break that.) And now that it's on the mailing lists, it can be considered part of Apple's official documentation. ;-) -Jeff ___ 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: Sending a Selector to another Class.
On Oct 22, 2009, at 9:54 am, Jeff Johnson wrote: Ignore bbum. We hereby promise never to break == for SEL. (But SEL is not char*. We will break that.) And now that it's on the mailing lists, it can be considered part of Apple's official documentation. ;-) It already is: http://developer.apple.com/mac/library/documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html#//apple_ref/c/func/sel_isEqual mmalc ___ 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
Sending a Selector to another Class.
How would I send a Selector to another class? I know to send it to a selector in the same file you do [self performSelector:@selector(doSomething)]; and for sending it to another class I've tried [otherClass performSelector:@selector(doSomethingElse)]; But I just get an error in the Debugger saying +[otherClass doSomethingElse]: unrecognized selector sent to class 0xe5c4 What have I done wrong? Thanks. ___ 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: Sending a Selector to another Class.
On Oct 21, 2009, at 12:23 PM, Joshua Garnham wrote: How would I send a Selector to another class? I know to send it to a selector in the same file you do [self performSelector:@selector(doSomething)]; and for sending it to another class I've tried [otherClass performSelector:@selector(doSomethingElse)]; But I just get an error in the Debugger saying +[otherClass doSomethingElse]: unrecognized selector sent to class 0xe5c4 What have I done wrong? You seem to be missing the very basics of Objective-C (and I'd dare to say object-oriented programming topics in general). You should (re) read the introductory material in the documentation and take advantage of places like cocoadevcentral.com (free articles) to get a handle on this. The Objective-C Programming Language http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/Introduction/introObjectiveC.html Cocoa Application Tutorial http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjCTutorial/01Introduction/01Introduction.html CocoaDev Central http://www.cocoadevcentral.com -- I.S. ___ 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: Sending a Selector to another Class.
On Wed, Oct 21, 2009 at 9:23 AM, Joshua Garnham joshua.garn...@yahoo.co.ukwrote: How would I send a Selector to another class? I know to send it to a selector in the same file you do [self performSelector:@selector(doSomething)]; Why not simply... [self doSomething] ? and for sending it to another class I've tried [otherClass performSelector:@selector(doSomethingElse)]; Why not simply [otherClass doSomethingElse] ? ...aka... Why are you using performSelector in the above? But I just get an error in the Debugger saying +[otherClass doSomethingElse]: unrecognized selector sent to class 0xe5c4 What have I done wrong? You are sending a message to an object that doesn't respond to that message (aka no implementation for it). The error message you listed should have more information about the class of the object you messaged incorrectly, what does the rest of it say? Hard to tell what may be going wrong with the limited information you have posted. I rather not waste time guessing (can think of at least 4 common things you could be doing wrong). -Shawn ___ 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: Sending a Selector to another Class.
Hi, That was all that showed up in the debugger, but in the class otherClass there is a method called doSomething. I have also tried what you suggested - [otherClass doSomethingElse] - but i get a warning in xcode, http://cld.ly/7c4la. (JGManagedObject is what replaces otherClass) Thanks. From: Shawn Erickson shaw...@gmail.com To: Joshua Garnham joshua.garn...@yahoo.co.uk Cc: cocoa-dev@lists.apple.com Sent: Wednesday, 21 October, 2009 18:02:55 Subject: Re: Sending a Selector to another Class. On Wed, Oct 21, 2009 at 9:23 AM, Joshua Garnham joshua.garn...@yahoo.co.uk wrote: How would I send a Selector to another class? I know to send it to a selector in the same file you do [self performSelector:@selector(doSomething)]; Why not simply... [self doSomething] ? and for sending it to another class I've tried [otherClass performSelector:@selector(doSomethingElse)]; Why not simply [otherClass doSomethingElse] ? ...aka... Why are you using performSelector in the above? But I just get an error in the Debugger saying +[otherClass doSomethingElse]: unrecognized selector sent to class 0xe5c4 What have I done wrong? You are sending a message to an object that doesn't respond to that message (aka no implementation for it). The error message you listed should have more information about the class of the object you messaged incorrectly, what does the rest of it say? Hard to tell what may be going wrong with the limited information you have posted. I rather not waste time guessing (can think of at least 4 common things you could be doing wrong). -Shawn ___ 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: Sending a Selector to another Class.
On Oct 21, 2009, at 10:02, Shawn Erickson wrote: But I just get an error in the Debugger saying +[otherClass doSomethingElse]: unrecognized selector sent to class 0xe5c4 You are sending a message to an object that doesn't respond to that message (aka no implementation for it). The error message you listed should have more information about the class of the object you messaged incorrectly, what does the rest of it say? The error message has enough information -- the +. The problem is that the OP sent an instance method selector to the class object, which obviously doesn't recognize it. That indicated a confusion between classes and instances (at a minimum), which drove I.S. into the well known demented-schoolmarm-handing-out-homework impersonation. :) ___ 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: Sending a Selector to another Class.
- Message from joshua.garn...@yahoo.co.uk - but i get a warning in xcode, http://cld.ly/7c4la. (JGManagedObject is what replaces otherClass) That one is usually a case of not importing the JGManagedObject header or not declaring the class method in that interface. ___ 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: Sending a Selector to another Class.
That selector is a unique index that points to a method of a specific class. Methods themselves belong to a specific class and can't operate outside of their classes. (They compile down to regular C functions that accept an additional object parameter.) So, it doesn't make sense to use one class's selector on another class. Maybe these two classes should inherit from a common parent that has the method you want to share. On Wed, Oct 21, 2009 at 12:23 PM, Joshua Garnham joshua.garn...@yahoo.co.uk wrote: How would I send a Selector to another class? I know to send it to a selector in the same file you do [self performSelector:@selector(doSomething)]; and for sending it to another class I've tried [otherClass performSelector:@selector(doSomethingElse)]; But I just get an error in the Debugger saying +[otherClass doSomethingElse]: unrecognized selector sent to class 0xe5c4 What have I done wrong? Thanks. ___ 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/jimkang%40gmail.com This email sent to jimk...@gmail.com ___ 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: Sending a Selector to another Class.
Ah, I see. so I need to send it to an instance of the class not the class it self. How would I do that? Thanks, Josh. From: Jens Alfke j...@mooseyard.com To: Jim Kang jimk...@gmail.com Cc: Joshua Garnham joshua.garn...@yahoo.co.uk; cocoa-dev@lists.apple.com Sent: Thursday, 22 October, 2009 6:21:29 Subject: Re: Sending a Selector to another Class. On Oct 21, 2009, at 9:43 AM, Jim Kang wrote: That selector is a unique index that points to a method of a specific class. No, that's not true of Objective-C (although it is of C++ method-pointers.) A selector is, basically, just a unique string: it defines a message, not a method, to use the old Smalltalk OOP terminology. Any class that implements a method with that name uses the same selector for it, regardless of inheritance. To be specific, if I create two unrelated classes A and B, each of which implements a -foo method, the selector @selector(foo) is used for both. Joshua's problem was, apparently, that he was trying to send an message to a class object instead of an instance, but the corresponding method was defined on instances, not the class. —Jens ___ 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
