CODEWITHSUNDEEP
objective-cnsmutablearrayprotocols
Lev Polyakov
Lev Polyakov

Reputation: 31

How to create NSMutableArray in which objects follow protocol?

How to create NSMutableArray in which objects follow protocol? For example in swift I can do something like: var array:[MyProtocol] = [] How to implement that in objC

Upvotes: 0

Views: 199

Answers (1)

CRD
CRD

Reputation: 53000

In Objective-C you declare a variable of protocol type by declaring it as id<SomeProtocol>, e.g.:

@protocol SomeProtocol<NSObject>
...
@end

@interface SomeClass : NSObject<SomeProtocol> // base class NSObject, implements SomeProtocol
...
@end

@implementation SomeClass
...
@end

// a variable declaration somewhere which holds a reference to any object
// which implements SomeProtocol
id<SomeProtocol> anyObjectImplementingSomeProtocol = SomeClass.new;

Using Objective-C's lightweight generics you can extend this to containers of protocol type, e.g.:

NSMutableArray<id<SomeProtocol>> someArray = NSMutableArray.new;

Warning: Lightweight generics are named that for a reason, it is quite easy to bypass the restrictions imposed by them, e.g. by adding an object which does not implement SomeProtocol to someArray. You don't get the same strong generics as in Swift.

HTH

Upvotes: 1

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