Question

I have a very simple Mac App built with XCode 4 (just a blank form for now).
Now I’ve added a button via Interface Builder and a method to my AppDelegate:

-(IBAction) btnScanClicked
{
    NSLog(@"Hello!");
}

When I start my App I get the following message:

Could not connect the action btnScanClicked: to target of class
AppDelegate

Does that mean I can’t add any event handlers to my AppDelegate? Where else could I put them, and how would I set that up with Interface Builder?

Answer 1

The problem is that you haven’t declared the action method properly. Replace the definition with:

-(IBAction) btnScanClicked:(id)sender {

Notice how the error message states that it couldn’t connect to btnScanClicked: That colon at the end isn’t punctuation – it’s says that the message takes a parameter.

Unlike UIKit action methods need to be of the form:

- (void)methodName:(id)sender

IBAction just resolves to void, but is an indicator to Interface builder that it is an method that can be hooked up by context dragging.