Extracting value from NSDictionary with brackets vs. objectForKey: or valueForKey:
<p>I was wondering what this convenience method stood for but was unable to find any answers for it.</p>

<p>What exactly does <code>theDictionary[@"key"]</code> do when wanting to extract a value from a dictionary? Is it using <code>valueForKey:</code> or <code>objectForKey:</code>?</p>

<p>What is better performance wise? Is it better to write the whole message like <code>[theDictionary objectForKey:@"key"]</code> or is the convenience method sufficient?</p>