NSUrlConnection 和 NSUrlRequest 的关系

An NSURLConnection object lets you load the contents of a URL by providing a URL request object. The interface for NSURLConnection is sparse, providing only the controls to start and cancel asynchronous loads of a URL request. You perform most of your configuration on the URL request object itself.

Note: Although instances of this class are commonly called “connections”, there is not a 1:1 correlation between these objects and the underlying network connections.

setURL:

setHTTPMethod:

setTimeoutInterval:

- (void)addValue:(NSString *)value forHTTPHeaderField:(NSString *)field

- (void)setHTTPBody:(NSData *)data