CODEWITHSUNDEEP
iphoneobjective-cios
John Lane
John Lane

Reputation: 1132

iOS check if object can be retained

I have a method with an id parameter in it. I also have an id as a property inside my class. My question is in the init method is there a way I can determine if the passed parameter can be retained so I can do something like: 

someProperty = [idParameter retain];

Thanks

Upvotes: 0

Views: 92

Answers (2)

Jim
Jim

Reputation: 73936

All Objective-C objects (i.e. anything inheriting from the NSObject class or implementing the NSObject protocol) implement retain. It's implemented by the NSObject class and it's a required method for the protocol, so you cannot have an Objective-C object that you cannot call retain on.

The only time you'd not be able to call it in these circumstances is if your variable of type id was not pointing to an Objective-C object. This would be a mistake, do not do this.

Upvotes: 3

FeifanZ
FeifanZ

Reputation: 16316

Every object that inherits from NSObject has a respondsToSelector: method. (Documentation)

Therefore, you could write:

if ([idParameter respondsToSelector:@selector(retain)])
    someProperty = [idParameter retain];

Upvotes: 2

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