NSURLConnection or NSurl?

what is the difference between NSURLConnection and NSURL?

i mean if i am downloading a file, does it make and difference wh开发者_如何学Cich one i use?

Rgds

for:

     NSString *myUrl = @"http://www.test.com/"; 
     NSString *returnData = [NSString stringWithContentsOfURL:[NSURL URLWithString: myUrl]]; 

or

     NSString *myUrl = @"http://www.test.com/"; 
     NSURLRequest *myRequest = [[NSURLRequest alloc] initWithURL: [NSURL URLWithString:myUrl] ]; 
     NSString *returnData = [NSURLConnection sendSynchronousRequest:myRequest returningResponse: nil error: nil ];  

whats the difference?

thks

• The Connection

  An NSURLConnection object provides support to perform the loading of a URL request.

• The Request

  NSURLRequest objects represent a URL load request in a manner independent of protocol and URL scheme.

  E.g. requestWithURL:

  Creates and returns a URL request for a specified URL with default cache policy and timeout value.

  + (id)requestWithURL:(NSURL *)theURL
  

• The URL

  The NSURL class provides a way to manipulate URLs and the resources they reference. NSURL objects understand URLs as specified in RFCs 1808, 1738, and 2732. ...

  To get the contents of a URL, NSString provides stringWithContentsOfURL: and NSData provides dataWithContentsOfURL:.

References:

• NSURLConnection_Class/Reference/Reference.html
• NSURL_Class/Reference/Reference.html#//apple_ref/doc/c_ref/NSURL

Best thing about NSURLConnection is its asynchronous behaviour so that you dont have to wait until the url is loaded.