will any change to the member of class observed set off the observer to the member?
<p>Let me make a example to show this:</p>

<p>I have a class <strong>ClassA</strong>, it contains a public member <strong>memberA</strong>.
it also contains a public method <strong>methodA</strong>, which will change the value of memberA.</p>

<p>now I have a instant of ClassA: </p>

<pre><code>instantA
</code></pre>

<p>then I call this:</p>

<pre><code>[instantA addObserver:anObserver forKeyPath:@"memberA" options:NSKeyValueObservingOptionNew context:NULL];
</code></pre>

<p>why this will touch off observer:</p>

<pre><code>instantA.memberA = xxxxx;
</code></pre>

<p>but this won't:</p>

<pre><code>[instantA methodA];
</code></pre>
