ios change UIButton image at runtime more than one time - cocoa-touch

Question

I am using storyboard and i want to do a 3 stars priority button, at the first view the stars will appear off (not shining and that is means priority =0), when you first press this button the image of the three not shining stars with change to one star shining, when you press this button again (which is the button with the 3 stars image background) one star will be shining and that means priority = 1 (the image changes), and the press # 2 two stars will be shining, and pressing again make the three stars shining, and in the next press it starts from beginning (none of the stars is shining).
I used this code to implement the button but i do not know how to change the image. any help ?
UIButton *btnTwo = [UIButton buttonWithType:UIButtonTypeRoundedRect];
UIImage *btnImage = [UIImage imageNamed:#"3star.png"];
[btnTwo setImage:btnImage forState:UIControlStateNormal];
btnTwo.frame = CGRectMake(40, 140, 240, 30);
[self.view addSubview:btnTwo];

Answer 1

Create a method which will be called when the button is pressed:
[btnTwo addTarget:self action:#selector(buttonPressed) forControlEvents:UIControlEventTouchUpInside];
and if you don't want to make a property declaration for the button add a tag identifier
btnTwo.tag = 3; //for ex.
in the method you created
-(void) buttonPressed{
UIButton *button = (UIButton*)[self.view viewWithTag:3];
[button setImage:[UIImage imageNamed:#"newImage.png"] forState:UIControlStateNormal];
}
In this method you could then provide logic to assign the correct image based on the number of times pressed.