NSURLConnection class, types and how to use.

 

There are two ways of using the NSURLConnection class. One is asynchronous, and the other is synchronous. An asynchronous connection will create a new thread and does its downloading process on the new thread. A synchronous connection will block the calling thread while downloading content and doing its communication. 
Many developers think that a synchronous connection blocks the main thread, but that is incorrect. A synchronous connection will always block the thread from which it is fired. If you fire a synchronous connection from the main thread, yes, the main thread will be blocked. But if you fire a synchronous connection from a thread other than the main thread, it will be like an asynchronous connection in that it won’t block your main thread. In fact, the only difference between a synchronous and an asynchronous con‐ nection is that the runtime will create a thread for the asynchronous connection, while it won’t do the same for a synchronous connection. 
In order to create an asynchronous connection, we need to do the following: 

1.    Have our URL in an instance of NSString. 
2.    Convert our string to an instance of NSURL. 
3.   Place our URL in a URL Request of type NSURLRequest, or in the case of mutable URLs, in an instance of NSMutableURLRequest. 
4.    Create an instance of NSURLConnection and pass the URL request to it.