Using the standard OpenGL ES iPad pattern we get such 'structure'. I've read some about delegating, protocols, but still got no direct answer for this particular purpose. Please enlighten me.
Why would I need this? Well all the action goes on in ES1Renderer and I want to [EAGLView setUserInteractionEnabled:true]; for example, which gives me:
'EAGLView' may not respond to
'+setUserInteractionEnabled:'
You're sending a message to a class, not an instance. You'd need an object of type EAGLview to send the setUserInteractionEnabled: message to.
Like:
EAGLView *myView;
[myView setUserInteractionEnabled:true];
Related
How can I do this?
I have ViewController 1, and ViewController 2.
ViewController 1 defines a protocol and ViewController 2 conforms to it.
I set ViewController 2 has a delegate and invoke a method in ViewController 1. This method runs fine. And send confirmation back to my ViewController 2.
I can exchange data between them, but I'm trying to figure out a way, to get data from a particular instance of ViewController 1, to ViewController 2.
Because when I'm using my delegate, to run a method in ViewController 1 it's not going for that particular instance that I'm interested in.
Is there a way I can resolve this?
Can I set my delegate, a delegate of a particular instance so I can get it's state? Is this possible? And if so, how?
In other words, can I target a specific instance with my delegate?
--
p.s. if I try to get data of a property ruled by ViewController 1, it come has nil (I think this is because I'm not targeting a particular instance)! One way I can resolve it, is have a method that reads "already saved data". But I would be replicating code, and instantiating new objects with data that is already available in previous ViewControllers.
Any help is most appreciated. Thank you in advance!
Nuno
edit:
SetupTableViewController *delegate = [[SetupTableViewController alloc] init];
[delegate setDelegate:self];
Every property I try to get from this point on forward, is nil. How can I target this to a particular instance of my previous ViewController? I do not want to instantiate a new SetupViewController. What I really need is to access an existing instance of my SetupViewController.
The question is really vague and you should probably post some code to better explain what you're trying to achieve.
"I can exchange data between them, but I'm trying to figure out a
way, to get data from a particular instance of ViewController 1, to
ViewController 2."
Well when you do myViewController1Instance.delegate = self; , any delegate call that you make will only be sent from myViewController1Instance object to ViewController2, not from the other instances of ViewController1 class.
instead of using delegation the way you are trying to do, which is a little bit akward, try using notifications instead.. when an instance knows that it needs to send something it throws a notification that it is caught by the view controller 2.
why do you have more than one instance of vc1 on the screen? can you give more info on what you are trying to achieve?
Add (UIViewController*)sender to your protocol messages.
On receipt of the message, check the sender, if it isn't the one you're interested in, just return.
I have to agree with Sorin though, you're probably better using notification.
Problems like these can often be fixed with architectural improvements. Always good to step back and think if the data is in the correct place.
In iOS and Cocoa Touch, sometimes it seems we can get by without calling super, such as:
-(void) viewDidAppear:(BOOL)animated {
// nothing weird if the following is not called:
// [super viewDidAppear: animated]
// but the docs says we should call it
}
and I think with drawRect, we usually won't send super that same message, unless the super is doing some drawing of its own. Is it true that we should always send super the same message just to be safe in Cocoa Touch and iOS, and are there cases, then, not not send super the same message?
There's no general rule, it always depends on the class you're subclassing and method you're overriding. NSObject is the root of the class hierarchy in (modern) Objective-C and obviously it doesn't implement most of the methods you see and use, so always calling super wouldn't make sense as a general rule.
You just have to check the documentation for each method separately.
You can't say this in general. Only one thing is sure: call super if you want the functionality that the method being overridden does, and don't call it if you don't.
i have been working on moving one of my apps away from the "shared appdelegate" process which seems to be frowned up, despite its over whelming use. i have been attempting to setup protocol methods for what i want to do but am having zero luck. my question is, can you even have lets say a single viewcontroller send delegate requests to multiple classes? from what im finding out it doesn't seem like you can. which doesn't make sense because i thought that was the whole point of delegates and protocols with mvc. now just to clarify, i know you can have a single viewcontroller act as the delegate for multiple other viewcontrollers. but that's not what i am asking. for a simple example, lets say you have apples flip-utility template. the "done" button just calls a delegate method to the mainvc to dismiss it. now lets say we added a new class called...
#interface NewClass : NSObject <TheOtherDelegate>
and it had a delegate method...
- (void)doSomething
{
NSLog(#"The Delegate did something...");
}
can we have a button on the flipsideviewcontroller, that we wanted to call that delegate method, but still keep the "done" button call to the delegate method on the mainviewcontroller that dismisses it?
that being said, i put together a quicky project just to see if it would work and it doesn't. i came across an "answer" that says you have to instantiate the class first you want to be the delegate...
NewClass *myDelegate = [NewClass alloc] init]
[fillInMethodHere setDelegate:myDelegate];
not sure why it got a correct answer check, because needless to say it doesn't work. is there something i am missing? i scoured ib to see if there is some "delegate" connection somewhere but i couldn't find anything.
on a side note, as i was working in my working project, i read a suggestion about removing the #import and adding #class. again, that broke all kinds of things. the strange thing is before doing that, what i had so far was working and building fine. when i removed the new #class and un-commented the #import. xcode all of a sudden gave me an error "cannot find protocol deceleration for..." but yet, it worked seconds earlier. i would up having to remove the protocol code and re-add it for it to work again. very starge.
any help would be appreciated. everything iv read in docs, google, stack, etc that say something should work, don't in an actual project.
A "delegate" isn't some fancy object. It's simply a synthesized property of type id called delegate. If you wanted to, you could have an arbitrary number of properties that all conformed to the same protocol. Then when you wanted to issue a callback, you would just address all of them:
[self.mydelegateA doSomething];
[self.mydelegateB doSomething];
etc.
You could also have an NSMutableArray property that you could add objects to, and then use [self.myMutableArrayOfDelegates makeObjectsPerformSelector:#selector(doSomething)].
Finally, there's always the route of NSNotificationCenter (not to be confused with push notifications) is a class that provides an inter-object messaging system. Many objects can register for a message that any other object can send.
Please see the Apple's documentation for more information. Click Here.
Regardless of the fact that this is OS X documentation, it's still quite good at explaining things visually: click here.
Here's an example of simply changing the name of the delegate property: click here
And here's an example of adding another protocol and a second delegate: click here
Finally, here's an example that builds on the previous two and has a third delegate that also conforms to the same protocol: click here
I use sharekit with mail/twitter/facebook and I am really new to objective-c. sharekit works well and sends my images like it should.
in my app I have a screenshot function. I want the app to 'freeze' when a screenshot is taken, stopping to send any shake- or touch-event to the scene behind the sharekit-action.
in my screenshot-layer I have three buttons which call the shareItem-methods of their specified service, like
[SHKTwitter shareItem:item];
vereything works fine 'till here. but now when the sending is finished (or canceled or errored) I need the app to 'unfreeze', sharekit should tell my app that it is allowed to listen to any touch- or shake-action again.
I am sorry but I think I don't understand the concept of using the delegate here. I mean, is 'sendDidFinish' meant to be inside a delegate? and if so, how could I tell sharekit who is its delegate? or do I have to edit the send-service classes (like SHKItem or SHKFacebook) itself?
please don't downrate me for this question. I really want to get behind this mystery...
SHKTwitter inherit from SHKOAuthSharer, who inherit from SHKSharer. SHKSharer has a delegate protocol called "SharerDelegate".
So you can use an instance of SHKTwitter, then set it's delegate as :
shkTwitterInstance.shareDelegate = yourDelegateObject.
And implement the delegate method
- (void)sharerFinishedSending:(SHKSharer *)sharer;.
Try that.
EDIT (OTHER, AND MORE POPULAR, SOLUTION)
Also, you can suscribe your object to "SHKSendDidFinish" notification from SHKTwitter object.
[[NSNotificationCenter defaultCenter] addObserver:yourObject selector:#selector(theMethodthatYouWantToExecuteWhenTheNotificationIsRaised:) name:#"SHKSendDidFinish" object:shkTwitterObject];
I am using UIViewController (a subclass of course) with a text field which sends an action when the contents changed (to the contentsChanged: selector of the ViewController). It is done by sending contentsChanged: to file's owner in IB.
But when I test it, it says : "-[NSCFString contentsChanged:] : unrecognised selector sent to instance " and the instance pointer in hex.
I am guessing that for some reason the view controller gets moved to another pointer and a string gets allocated there, but I cannot figure why.
Any ideas ?
Sounds like a classic case. Read up on NSZombieEnabled for how to track this sort of problem down.
I have the exact same problem with a subclass of UIViewController and this piece of innocuous code:
- (void)viewDidLoad
{
NSLog(#"%# %s %#", [self class], _cmd, answerButton);
[self.answerButton addTarget:self
action:#selector(getAnswerToQuestion:)
forControlEvents:UIControlEventTouchUpInside];
}
Yes, answerButton is connected (it's an IBOutlet), yes, - (IBAction)getAnswerToQuestion:(id)sender; is a proper method, but no joy. When I commented out the viewDidLoad and made the connection in IB, it showed in the crash report that the failure happens on [UIControl sendAction:to:forEvent:] resulting in
objc_msgSend() selector name: performSelector:withObject:withObject:
I can't prove it, but I suspect there's a bug somewhere in the UIKit that translates the bindings and addTarget to a call to performSelector. I'm planning to upgrade to iOS 4.01 first to see if that won't solve the problem.
UPDATE:
I'm not sure anymore that my problem really is similar to Alexandre Cassagne's but in the interest of sharing information I will not delete it just yet. I solved my problem, as so often, when I started to make an example project in order to file a bug report. Yes, clicking made answerButton call getAnswerToQuestion: like a good little object and all was fine.
The difference between the subclassed UIViewController of the example project and that of my real project was that the first also functioned as the xib's File's Owner while the second was just one of several view controller. When I moved getAnswerToQuestion: to the File's Owner in my real project, clicking answerButton worked as expected. So, my hunch that the problem lay somewhere in the translation from binding to performSelector wasn't that far off: the problem lies in the Responder Chain. I would think that establishing the Action-Target link either programmatically or in IB would bypass the Responder Chain, but apparently not.
The problem now, of course, is that Alexandre states in his question that his contentsChanged: method already is part of the File's Owner, which makes my answer irrelevant to the question.
without looking at the code, it looks like you are calling contentsChanged: on the text field's text, instead of the UIViewController subclass.
you should consider using the UITextFieldDelegate protocol to get called back when the text of a UITextField changes. I have not looked, but this is the thing I would do off the top of my head.