iPhone: Sharing protocol/delegate code

Question

I have the following code protocol snippets:

@protocol FooDelegate;

@interface Foo : UIViewController { id delegate; } ...

@protocol FooDelegate ... // method 1 ... // method 2 ... @end

Also, the following code which implements FooDelegate:

@interface Bar1 : UIViewController { ... }

@interface Bar2 : UITableViewController { ... }

It turns out the implementation of FooDelegate is the same on both Bar1 and Bar2 classes. I currently just copy FooDelegate implementation code from Bar1 to Bar2.

How do I structure/implement in such a way that Bar1 and Bar2 share the same code in a single code base (not as currently with 2 copies) since they are the same?

Thanks in advance for your help.

Answer 1

Make a new object, MyFooDelegate:

@interface MyFooDelegate : NSObject <FooDelegate>

Then Bar1 and Bar2 can each create an instance of it (or share one instance). In those classes you can eliminate the delegate methods and add lines like:

MyFooDelegate *myDooDelegateInstance = ...;

foo.delegate = myFooDelegateInstance;

You could also create an instance of MyFooDelegate in a NIB file and connect the view controller's delegate outlets to it, if desired.

That way, you won't have any duplicated code in your source files or in your executables.

Answer 2

Option A: Implement the method in a Category

Any properties used must be declared in UIViewController.

UITableViewController is a subclass of UIViewController.

//UIViewController+MyAdditions.h
@interface UIViewController (MyAdditions)
- (void)myCommonMethod;
@end

//UIViewController+MyAdditions.m

@implementation UIViewController (MyAddtions)
- (void)myCommonMethod {
// insert code here
}

The new method added to UIViewController will be inherited by Bar1 and Bar2

Option B: Create a MyViewControllerHelper class

If you can, implement your common code as a class method, otherwise you will need to create an instance of your helper class either temporarily or as a property of Bar1 and Bar2

@interface MyViewControllerHelper : NSObject
- (void)myCommonMethod;
@end

@implementation MyViewControllerHelper
- (void)myCommonMethod {
    // common code here
}

@interface Bar1 : UIViewController {
MyViewControllerHelper *helper;
}
@property MyViewControllerHelper *helper;
@end

@implementation Bar1
@synthesize helper;
- (void)someMethod {
    [helper myCommonMethod];
}
@end

@interface Bar2 : UITableViewController {
MyViewControllerHelper *helper;
}
@property MyViewControllerHelper;
@end

@implementation Bar2
@synthesize helper;
- (void)someOtherMethod {
    [helper myCommonMethod];
}
@end