Protocol types within NSMutableArray

Question

I am trying to introduce some generics-style approaches from .NET into my iOS development. I am retrieving a list of custom objects of type Example.

I have defined a protocol that Example class implements:

@protocol ExampleProtocol
@property(nonatomic,assign) int Id;
@property(nonatomic,copy)NSString *Description;
@optional
@property(nonatomic,copy)NSString *Icon;
@end

I then retrieve my NSMutableArray of Example as follows:

id<ExampleProtocol> anExample = [arrayOfExampleProtocols objectAtIndex:0];

The problem I have is that anExample is always empty regardless of the contents of the NSMutableArray. My ultimate aim is to be able to reference the properties with the following syntax:

id<ExampleProtocol> anExample = [arrayOfExampleProtocols objectAtIndex:0];
NSString *test = [anExample Description];

I am willing to put money on the fact that you never initialized your mutable array because if `anExample` were "empty" (I'm assuming you mean `nil`) your code would crash due to an index out of range exception. — Joe, Aug 17 '12 at 20:56

score 0 · Accepted Answer · edited May 23 '17 at 10:24

0

There are no generics in Obj-C. The "protocol" is a messaging mechanism. Please see this post: No Generics in Obj-C

edited May 23 '17 at 10:24

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answered Aug 17 '12 at 23:38

TrevorL

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Protocol types within NSMutableArray

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