Re: [Obj-C Compiler Bug?] Two different classes declaring a message with the same name - compiler warning

FROM : Chris Suter
DATE : Tue Oct 14 13:11:18 2008

On Tue, Oct 14, 2008 at 9:13 PM, Graham Cox <graham.<email_removed>> wrote:

> Isn't the problem here with the init method, rather than alloc?


It's a problem with both.

> NSString et. al. return id because they are class clusters (and because it's the
> established convention),


I believe the fact that they are class clusters is irrelevant; it's an
implementation detail. The objects returned still conform to the
interfaces defined by NSString and NSMutableString. They return id,
rather than NSString say, because otherwise you'd get a compiler
warning if you tried to do something like:

    NSMutableString *string = [NSMutableString string];

> but for your own classes, you could define your
> init... method to return the specific object type.


You can't override the type for existing methods. For example,
initWithString: always returns an id. You can define them as returning
something different but the compiler will ignore it.

> Best solution is just not to make the methods look the same.


That's not always convenient. For example, it's nice to be able to do
[NSString initWithString:] and [NSMutableString initWithString:].

-- Chris