title: How to pass a variable to a UIButton action
body: <p>I want to pass a variable to a UIButton action, for example</p>
  
  <pre><code>NSString *string=@"one";
  [downbutton addTarget:self action:@selector(action1:string)
       forControlEvents:UIControlEventTouchUpInside];
  </code></pre>
  
  <p>and my action function is like:</p>
  
  <pre><code>-(void) action1:(NSString *)string{
  }
  </code></pre>
  
  <p>However, it returns a syntax error.
  How to pass a variable to a UIButton action?</p>