CODEWITHSUNDEEP
objective-c
Zoltan Varadi
Zoltan Varadi

Reputation: 2488

Objective-C cast baseclass object into specific class

I'm very new in objective C and i want to know if/how what i would like to do is possible. I have a few classes

    @interface A: NSObject
{
    NSString*  Aa;
    NSUInteger Ab;
}

    @interface B: A
{
    NSString*  Ba;
    NSUInteger Bb;
}

    @interface C: A
{
    NSString*  Ca;
    NSUInteger Cb;
}

I want to create a function where i expect 'A' type of object and in the implementation check if their type is B or C later. Here's what i want:

-(void)doSomething:(A *param)
{
    //do some stuff
    if(param is an instance of B)
    {
        //do stuff with B
    }
    else
    {
        //do stuff with C
    }
}

How can it be done?

Sincerely,

Zoli

Upvotes: 3

Views: 3306

Answers (2)

Juri Pakaste
Juri Pakaste

Reputation: 1442

There's four methods you might want to use:

  • isKindOfClass: tests if an object is a member of class or subclass
  • isMemberOfClass: same as above, but more specific, doesn't allow subclasses
  • respondsToSelector: test if an object responds to a given selector, like [param respondsToSelector:@selector(method:)]. Useful for duck typing.
  • conformsToProtocol: test if object implements a protocol.

Upvotes: 6

Ricard Pérez del Campo
Ricard Pérez del Campo

Reputation: 2417

Check NSObject's method isKindOfClass:(Class)c You would do this:

-(void)doSomething:(A *)param
{
    //do some stuff
    if([param isKindOfClass:[B class]])
    {
        //do stuff with B (cast will be required to avoid warnings!)
        B *castedB = (B *)param;
        //...
    }
    else if ([param isKindOfClass:[C class]])
    {
        //do stuff with C
        C *castedC = (C *)param;
        //...
    }
}

Hope this help!

Upvotes: 6

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