Objective-C "Expression result unused"

Question

I have declared a BOOL and am flipping it's value when a user presses a button.

I do so like this: !self.isEditing;, but XCode warns me "Expression result unused"

Can this cause problems? Should I instead do: self.isEditing = !self.isEditing;?

Answer 1

When you run !self.isEditing, you're not actually changing the value of self.isEditing. So, yeah, you should use self.isEditing = !self.isEditing.