natomic, readwrite, strong) id&lt;NSObject&gt; key</code></div>

		    
			

			

			

			
			<div class="method-subsection discussion-section">
				<h4 class="method-subtitle">Discussion</h4>
				<p>An object that implements the isEqual: method of the NSObject protocol.
This can be used to identify a card, and is meant to be unique.</p>
			</div>
			

			

			

			
			<div class="method-subsection declared-in-section">
				<h4 class="method-subtitle">Declared In</h4>
				<p><code class="declared-in-ref">BT