Don't dismiss NSAlert when button is clicked

Question

I'm showing an NSAlert with a custom view and three buttons. The custom view has two text fields and it allows the user to log in.

In the Mac App Store, an NSAlert with a similar design comes up. When the user clicks the sign in button, the NSAlert does not dismiss (until the credentials are verified). How does Apple keep the alert up?

Answer 1

Get the NSButton you want to behave differently. Change its target and action. (To call through to the original target/action, preserve them before you change them.)

NSAlert *alert = ...;
NSButton *button = [[alert buttons] objectAtIndex:...];

id oldTarget = [button target];
SEL oldAction = [button action];
[button setTarget:self];
[button setAction:@selector(verifyCredentials:)];

Alternatively, you may want to build the alert as a custom window controller and XIB (which is how Apple did it in the case of the App Store.) In that case, you have fine-grained control over button behaviour.