Should I duplicate delegates declaration in the #interface () block like this:
.h file
#interface VKStartScreen : UIViewController <UIAlertViewDelegate, VKSdkUIDelegate>
#end
.m file
#interface VKStartScreen () <UIAlertViewDelegate, VKSdkUIDelegate>
#end
Or can I just omit it in the .m file?
You can omit in either file. You only need it in one place. I personally put the delegate declarations in the .m unless some other classes need to know that this class conforms to these protocols. Always opt for private and if it needs to be public for some reason open it up.
Related
This question already has answers here:
Where to put iVars in "modern" Objective-C?
(5 answers)
Closed 6 years ago.
I'm a beginner to Objective-C, coming over from Swift. It seems as if there are two different #interface instances in which I can declare my ivars. One in my header file, such as this:
// Header file
#interface ViewController : UIViewController
{
// declare instance variables
}
#end
And another that I can add in my implementation file, such as this:
// Implementation file
#interface ViewController ()
// declare instance variables
#end
#implementation ViewController
#end
EDIT: I was learning the "old way" of doing things, which taught me to declare private ivars in the .h file. My confusion stemmed from seeing ivars declared in .h (old way) as well as in .m (new, preferred way). Here's what I've learned (so far...):
// .h
#interface SomeClass : UIViewController
#property (nonatomic, assign) BOOL someBool;
// declare other properties, which will all be public
#end
// .m
#interface SomeClass () <UITextFieldDelegate>
// what do I declare here?...
#end
#implementation SomeClass {
// ...and what do I declare here?
}
// method implementations
#end
However, I'm still confused as to the difference between my .m's #interface and the #implementation curly brackets. #matt said to never use curly brackets, but #rmaddy's answer here suggests that #implementation SomeClass {} is ok. So, which is it?
Do you want it to be accessible publicly? Then write in .h file.
If you don't want other classes to see it ie you want to make it private and only visible to that class itself then write in .m file.
For more information you can see this question:
Where to put iVars in "modern" Objective-C?
I m trying to passing values from second class to first class for that I am using protocol and delegate process. Whenever I run my program I am facing below Issue.
No Type or Protocol Named 'locateMeDelegate'
Viewcontroller A .h
#interface first : UIViewController < locateMeDelegate > { }
In my case the issue was caused by importing the delegate's header file to the delegator's class .h file. This seems to create a sort of vicious circle. As soon as I deleted the import statement of the delegate's header from the delegator's .h file, the error went away.
Tipically, if you intend your protocol to be used by other classes you must declare it in the header file like this:
// MyClass.h
#protocol MyProtocol;
#interface MyClass : NSObject
#end
#protocol MyProtocol
- (void) doSomething: (MyClass*) m;
#end
After you declare it, you should implement the methods of the protocol in the implementation file, which should conform to the protocol like this:
// MyClass.m
#implementation MyClass <MyProtocol>
pragma mark - MyProtocol methods
- (void) doSomething: (MyClass *)m {
// method body
}
#end
After these two steps you're ready to use you protocol in any class you desire. For example, let's say we want to pass data to MyClass from other class (e.g. OtherClass.h). You should declare in OtherClass.h a property so that we can refer to MyClass and execute the protocol. Something like this:
// OtherClass.h
#import MyClass.h
#interface OtherClass : NSObject
#property (weak) id<MyProtocol> delegate;
#end
You don't forget to import the header file where you declared your protocol, otherwise Xcode will prompt No Type or protocol named "MyProtocol"
id<MyProtocol> delegate; means you can set as the delegate of OtherClass any object (id) that conforms to the MyProtocol protocol (<MyProtocol>)
Now you can create an OtherClass object from MyClass and set its delegate property to self. Like this:
// MyClass.m
- (void)viewDidLoad() {
OtherClass *otherClass = [[OtherClass alloc] init];
otherClass.delegate = self;
}
It's possible to set the delegate to self because the delegate can be any object and MyClass conforms to MyProtocol.
I hope this can help. If you want to know more about protocols you can refer to this two websites:
Working with Protocols - Apple Documentation
Ry's Objective-C Tutorial (This one is easy to pick up)
I also faced the same issue and it seems the error is from Xcode itself. Please Try running on Physical device. This would solve the issue faced.
i want to know if the following situation can be done. I have inherited a project of iOS 8. I'd like to add a method to NSObject so that all objects can see it. and I have done this already. Here is the category implementation i have created:
#import "NSObject+myCategory.h"
#implementation NSObject (myCategory)
-(void)localizeStringIncludeDefault{
NSLog(#"about to localize String");
}
#end
Now i go to a MyViewController.m for example and try to call the method but its not working its not seen:
heres the .h:
#import <UIKit/UIKit.h>
#interface MyViewController : UIViewController {
BOOL someFakeBoolean;
IBOutlet UIView *someView;
//etc
}
#property (nonatomic,assign) IBOutlet MyViewController *myViewController;
-(void)localizeStringIncludeDefault;
and here is the implementation *.m and my issue:
#implementation MyViewController
- (void) viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self localizeStringIncludeDefault] //this call cant be done, the method is not visible
}
- (void) viewDidDisappear:(BOOL)animated
{
//etc
}
//etc
I mean it makes sense to me that i'd have to import the "NSObject+myCategory.h" into the MyViewController header to use the category but because i've inherited this code it already has a base. I dont want to go into every .h file and import this. Is a easy way to extend object so that EVERY object class sees my method ?
One option would be to add the category .h file to the pch file. Then it will be seen by every class in your project without the need to import it explicitly.
Declare your global variables or declarations in your pch file or rather make a Global.h and just import this in your pch file (helps a lot in reusability). You can declare extern items as well in your Global.h and populate in App Delegate
I just got started working with delegates.
from some reason I cannot do it, and I see errors.
I tried to do the next code on a new project and it was OK, but when i'm moving this code to my main project I have a few issues.
my NSObject class .h:
#protocol myNSObjectClassDelegate <NSObject>
#required
-(void)doSomething;
#end
#interface GeneralMethods : NSObject
#property (nonatomic,strong) id<myNSObjectClassDelegate> delegate;
#end
my NSObject class .m:
#synthesize delegate;
-(void)SomeMethod {
if ([delegate respondsToSelector:#selector(doSomething)]) {
[delegate doSomething];
}
}
my UIViewController .h
#import "GeneralMethods.h"
#interface view : UIViewController<UIGestureRecognizerDelegate,
UINavigationControllerDelegate,
 UIImagePickerControllerDelegate,
myNSObjectClassDelegate>
The error is here at .h - Cannot find protocol declaration for 'myNSObjectClassDelegate'
my UIViewController .m
-(void)doSomething{
}
What am I doing wrong?
EDIT : I figure it out:
For some reason, at my NSObject class, if I'm moving the #import myUIViewcontroller after this:
#protocol myNSObjectClassDelegate <NSObject>
#required
-(void)doSomething;
#end
the problem solved.
We can't see all the code but after reading some more of the exchanges it looks like dependencies are maybe added out of order. I recommend moving the protocol into its own file and #import'ing it to all the places that use it. This way you definitely will be importing things in the order you expect.
In addition to that, the following property declaration:
#property (nonatomic,strong) id<myNSObjectClassDelegate> delegate;
Delegates should be declared as weak, not strong.
#property (nonatomic,weak) id<myNSObjectClassDelegate> delegate;
The reason is to avoid retain cycles/memory leaks. Typically, though not always the relationship looks like this:
Parent Object (usually Controller) -----STRONG-----> Child (View often)
View Thing ----WEAK--------> delegate (actually the Parent Object)
Now if the relationship is STRONG both ways, releasing the parent from all who own it will not be sufficient to release it since its child also holds an owning relationship to it.
Also you can omit the:
#synthesize delegate;
Auto property synthesis renders this obsolete.
Make sure to import your NSObject class .h. file into your UIViewController's .h file (or wherever you declare the protocol). As it stands, you haven't imported the header that declares the protocol so your view controller has no way of knowing that it exists.
Ex:
#import "FileWithProtocol.h"
#interface MyClass <MyProtocol>
...
#end
In the view controller .h file, try adding this line:
#protocol MyNSObjectClassDelegate;
before
#interface ...
I have started new iOS project and have added only one property in ViewControler header file. but it gives me error:
expected specifier-qualifier-list before 'property'
here is the code:
#import <UIKit/UIKit.h>
#interface QuoteGenViewController : UIViewController {
#property (retain) NSArray *myQuotes;
}
#end
Here the general structure of a class interface
#interface Class : Superclass
{
// Instance variable declarations.
// Theirs definition could be omitted since you can declare them
// in the implementation block or synthesize them using declared properties.
}
// Method and property declarations.
#end
Since a property provides a simple way to declare and implement an object’s accessor methods (getter/setter), you need to put them in the Method and property declarations section.
I really suggest to read ocDefiningClasses doc for this.
Hope that helps.
Your code should look like this:
#import <UIKit/UIKit.h>
#interface QuoteGenViewController : UIViewController {
}
#property (retain) NSArray *myQuotes;
#end