Question

I am trying to print “.” when I press on a button that shows “.”

Basically I wanna grab “.” on NSString format

So if I do

NSString *dec = [sender currentTitle];

it just crashes when I try to run.

Answer 1

In Cocoa, all controls send notifications that they have been operated, by using a target-action mechanism. The ‘target’ is any other object and the ‘action’ is any selector that that object responds to. Buttons are no different.

So you can, for example, define:

-(void)buttonClicked:(id)sender {
  NSLog(@"Button was clicked!");
}

You’d hook that up to the button’s target-action, by invoking -setTarget: and -setAction: accordingly. The target will be self, if you’re doing this from inside the class that handles the action:

[button setTarget:self];
[button setAction:@selector(buttonClicked:)]

Now when the button is pressed, you’ll get a NSLog() output in the console.

To update the value of a label instead of printing something with NSLog(), you can probably figure that out, but:

-(void)buttonClicked:(id)sender {
  [label setText:@"."];
}

You should read Apple’s documentation, which covers this stuff in great detail.

https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CocoaFundamentals/CommunicatingWithObjects/CommunicateWithObjects.html#//apple_ref/doc/uid/TP40002974-CH7-SW14

PS: stackoverflow is for all programming languages, so make sure to tag your questions with the relevant programming language.