Use compiler conditional to control delegate implementation?

Question

Is it possible to use a compiler directive to control if a particular delegate is implemented?

For example, in the following code, I only want to include a library if we're a constant is defined:

#ifdef kShouldLoadFromCSV
#import "CHCSVParser.h"
#endif

@interface MyAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate, CHCSVParserDelegate>{

If kShouldLoadFromCSV is undefined, I don't want to implement CHCSVParserDelegate. I've tried sticking the compile directive in the interface declaration, but that didn't work.

Is there a way to do this?

Answer 1

You could do this:

#if kShouldLoadFromCSV
    @interface MyAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate, CHCSVParserDelegate>{
#else
    @interface MyAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate>{
#endif

---

Or if you wish, maybe harder to read, a matter of taste:

    @interface MyAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate
#if kShouldLoadFromCSV
      , CHCSVParserDelegate
#endif
>{

You have to remember that the preprocessor isn't syntax aware, it will just affect the input of the compiler.

Answer 2

To provide yet another formatting option:

@interface MyAppDelegate : NSObject
#if kShouldLoadFromCSV
    <UIApplicationDelegate, UITabBarControllerDelegate, CHSVParserDelegate>
#else
    <UIApplicationDelegate, UITabBarControllerDelegate>
#endif
{
...
}

But as you can already see, it's totally a matter of taste. I'd use something like the next one, since it's easier to extend it (e.g. imagine you'd need another conditional category...):

@interface MyAppDelegate : NSObject
<
    UIApplicationDelegate, UITabBarControllerDelegate
#if kShouldLoadFromCSV
    , CHCSVParserDelegate
#endif
> {
...
}

Answer 3

You can try something like:

@interface MyAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate >{
#if kShouldLoadFromCSV
    , CHCSVParserDelegate
#endif
> {