NSConcreteData vs NSData
<p>I have added an extension to NSData (base64 extension), which I kept over a separate infrastructure class lib project. But when i use this method from my main project i am getting an error like this: "-[NSConcreteData encodeBase64]: unrecognized selector sent to instance 0x121e60'".</p>

<p>But if i keep the same class in my main project itself, this will execute with out any issue.</p>

<p>I call this method in the following way: 
[dev setToken:[token encodeBase64]]; </p>

<p>Please suggest why this is not working if i put the extension in another project. (I am already using some other extensions, eg. for NSDate,  like this with out any issue.)</p>
