Private ivar in @interface or @implementation

Question

Is there any reason to declare a private ivar in @interface instead of @implementation?

I see code like this all over the internet (includi

Answer 1

Declaring instance variables in the @implementation is a recent feature of Obj-C, this is why you see a lot of code with them in the @interface - there was no other choice.

If you are using a compiler which supports declaring instance variables in the implementation declaring them there is probably the best default - only put them in the interface if they need to be accessed by others.

Edit: Additional Info

Instance variables declared in the implementation are implicitly hidden (effectively private) and the visibility cannot be changed - @public, @protected and @private do not produce compiler errors (with the current Clang at least) but are ignored.