CODEWITHSUNDEEP
objective-cobjectcastingnsnotifications
SundayMonday
SundayMonday

Reputation: 19737

Is casting ever required for the object on an NSNotification?

When I receive an NSNotification do I ever need to cast notification.object? Suppose I know notification.object will be an instance of MyClass and I do the following:

MyClass *myClass = notification.object;

Is any casting necessary here? How is the above assignment different from:

MyClass *myClass = (MyClass *)notification.object;

Upvotes: 2

Views: 160

Answers (2)

jscs
jscs

Reputation: 64002

No, it is entirely unneccessary and does not change anything about the behavior of your program. Casting only happens at compile time, and in the case of pointers, is just used to assure the compiler that you know what type the object is.

The compiler may complain about an assignment if you are, for example, setting a variable of type Subclass to the result of a method that returns type Superclass, where you know that the actual object you are going to get back is of type Subclass. In that case, you would cast to the subclass. E.g.,

MyViewController * vc = (MyViewController *)[someWindow rootViewController];

The type of notification.object is id, a generic object pointer, and the compiler is perfectly happy to assign such a pointer to any other type of pointer.

Upvotes: 4

jlehr
jlehr

Reputation: 15597

No. Objective-C doesn't require a cast from type id to another object type.

Upvotes: 2

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