"unrecognized selector sent to instance" error in Objective-C

It looks like you're not memory managing the view controller properly and it is being deallocated at some point - which causes the numberButtonClicked: method to be sent to another object that is now occupying the memory that the view controller was previously occupying...

Make sure you're properly retaining/releasing your view controller.

For those getting here via Google like I did, which probably pertains more to Xcode 4.2+/iOS 5+ more, what with ARC. I had the same error "unrecognized selector sent to instance". In my case I had a UIButton's target action set up to pass itself as the sender parameter, but later realised I didn't need it and removed that in code. So, something like:

- (IBAction)buttonPressed:(UIButton *)sender {

Was changed to:

- (IBAction)buttonPressed {

Right clicking the UIButton in question showed that the Touch Up Inside event was associated with the view controllers buttonPressed: method. Removing this and reassigning it to the modified method worked a treat.

This was the top Google answer for this issue, but I had a different cause/result - I thought I'd add in my two cents in case others stumble across this problem.

I had a similar issue just this morning. I found that if you right click the UI item giving you the issue, you can see what connections have been created. In my case I had a button wired up to two actions. I deleted the actions from the right-click menu and rewired them up and my problem was fixed.

So make sure you actions are wired up right.