Question

Is there a cast keyword in Objective-C like C# (as):

Foo bar = new Foo();
Foo tmp = bar as Foo;

Is this possible in Objective-C?

Answer 1

There is no direct equivalent of as in Objective-C. There is regular type casting (C-style).

If you want to check the type of the object, be sure to call isKindOfClass:.

To write the equivalent of:

Foo bar = new Foo();
Foo tmp = bar as Foo;

You’d write:

Foo *bar = [Foo new];
Foo *tmp = ([bar isKindOfClass:[Foo class]]) ? (Foo *)bar : nil;

You could always write this up as a category like:

@implementation NSObject (TypeSafeCasting)

- (id) asClass:(Class)aClass{
   return ([self isKindOfClass:aClass]) ? self : nil;
}

@end

Then you could write it like:

Foo *bar = [Foo new];
Foo *tmp = [bar asClass:[Foo class]];