How to conditionally conform to delegate protocol?

Question

If I am including frameworks in my iOS project that are only available in (for example) iOS 9, but I am still supporting iOS 8, how do I conditionally conform to a delegate protocol depending on the iOS version? For example, I understand I can include the framework conditionally like this:

#import <Availability.h>
#ifdef __IPHONE_9_0
#import <Something/Something.h>
#endif

But what if that framework also needs to conform to a delegate protocol?

@interface ExampleController () <UITextViewDelegate, SomethingDelegate>

How do I only include "SomethingDelegate" if I'm on iOS 9?

Thanks!

score 2 · Accepted Answer · edited May 23 '17 at 11:58

2

Well, in roughly the same manner:

@interface ExampleController () <UITextViewDelegate
#ifdef __IPHONE_9_0
     , SomethingDelegate
#endif
>

By the way, this is not the way you should check if the device is running iOS 9 - this only checks if your Xcode supports iOS 9.

edited May 23 '17 at 11:58

Community

1
1

answered Jul 23 '15 at 20:30

Glorfindel

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Oh my, I've been mislead. Thank you! I will accept as soon as it lets me. – user4034838 Jul 23 '15 at 20:36

score 1 · Answer 2 · answered Jul 23 '15 at 20:45

The answer of @Glorfindel is more clean, and I would support it, but just to have an alternative answer.

#ifdef __IPHONE_9_0
    #import <Something/Something.h>
    #define DELEGATES UITextViewDelegate, SomethingDelegate
#else
    #define DELEGATES UITextViewDelegate
#endif

@interface ExampleController : UIViewController <DELEGATES>

And there is also a question, what are you going to do with methods belonging to SomethingDelegate protocol, also #ifdef/#endif or just keep them "as is", as they never be called.

score 1 · Answer 3 · answered Jul 23 '15 at 22:55

This is a good task for a category, with its own files. The contents of those files can be entirely ifdefd out.

//ExampleController+SomethingDelegate.h
#ifdef __IPHONE_9_0

#import <Something/Something.h>

@interface ExampleController (SomethingDelegate) <SomethingDelegate>
@end
#endif

//ExampleController+SomethingDelegate.m
#import "ExampleController+SomethingDelegate.h"

#ifdef __IPHONE_9_0

@implementation ExampleController (SomethingDelegate) <SomethingDelegate>

 - (BOOL)somethingShouldMakePancakes:(Something *)something;    

@end

#endif

This reads much better than splitting the declaration across multiple lines with a macro in the middle, and keeps all the relevant methods in one place, under one ifdef.

How to conditionally conform to delegate protocol?

3 Answers3

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