Re: NSInvocation question

FROM : Nir Soffer
DATE : Mon Feb 25 21:49:45 2008

On Feb 21, 2008, at 18:22, Hank Heijink wrote:
> I have a document-based application, and my NSDocument subclass 
> runs an experiment which amounts to invoking NSInvocations based on 
> certain conditions. These NSInvocations retain their arguments, and 
> the target of the NSInvocation is the NSDocument subclass. I need 
> to record these invocations as well, so I made a class MVAction as 
> follows:
>
> @interface MVAction : NSObject <NSCoding> {
>     NSInvocation *action;
>     double invocationTime;
>     NSString *type;
>     NSArray *arguments;
> }
>
> The type is a string representation of the selector used in the 
> NSInvocation and the arguments are the arguments of the 
> NSInvocation. I did it like this because you can't encode an 
> NSInvocation, and I don't need the actual invocation anyway. My 
> document has an instance variable NSMutableArray *actions in which 
> these MVActions are stored.
>
> The problem I have is this: when I close my document, it isn't 
> deallocated. If the invocations don't retain their arguments, that 
> problem is gone, but I do need to retain them. What's a good way to 
> solve this? I could release the NSInvocation *action when I put an 
> MVAction in the array, but I wonder if there's a better method.


Another fix (re-reading the docs helps) - you can create an 
invocation without a target, since you don't want to retain the 
target in this case, and the target is known anyway. Then you can use 
-invokeWithTarget:myDocument instead of -invoke.

The docs don't tell if -invokeWithTarget: will retain the target, so 
call -setTarget:nil after invoking to be sure you don't create a 
retain cycle.


Best Regards,

Nir Soffer