No visible @interface for

Question

I have gotten this error on several occasions and am unclear as to what causes the error in general. After looking for over an hour on stack overflow and google I still don\

Answer 1

There are lots of reasons it could happen, but generally it's saying that at the line of code it flags, it doesn't see any evidence that the selector you are referencing is in the interface of the type it thinks the object has.

In this example,

No visible interface error

They declared operandStack with the wrong type.

In this one

http://www.raywenderlich.com/forums/viewtopic.php?f=2&t=3312

They had a typo in the selector name