title: what does "expression result unused" mean?
body: <p>I solved the problem by following the links that appear when you start a question<br>
  they told me how, but not why...<br>
  so my question is to understand compiler warning language</p>
  
  <p>In Xcode<br>
  I wanted a button that triggers an AlertView to assume the result of what the user enters therein:</p>
  
  <pre><code>UITextField *textfield = [alertView textFieldAtIndex:0];
  circumference = [textfield.text floatValue];
  NSString *myString = textfield.text;
  [_myButton setTitle:(@"%@",myString) forState:UIControlStateNormal];
  </code></pre>
  
  <p>Well, it works, plus a warning.<br>
  I should pose my question here so: 
  the warning said "Expression Result Unused". How do they figure that? I was using the result of the expression - right there on the button.</p>
  
  <p>for those concerned, this is the fix:</p>
  
  <pre><code>UITextField *textfield = [alertView textFieldAtIndex:0];
  circumference = [textfield.text floatValue];
  [_myButton setTitle:[NSString stringWithFormat:@"%@",textfield.text] forState:UIControlStateNormal];
  </code></pre>