NSURLConnection
常用類：
NSURL：請(qǐng)求地址
NSURLRequest：一個(gè)NSURLRequest對(duì)象就代表一個(gè)請(qǐng)求砰识，它包含的信息有
一個(gè)NSURL對(duì)象
請(qǐng)求方法恩掷、請(qǐng)求頭茴晋、請(qǐng)求體
請(qǐng)求超時(shí)
… …
NSMutableURLRequest：NSURLRequest的子類
NSURLConnection
負(fù)責(zé)發(fā)送請(qǐng)求，建立客戶端和服務(wù)器的連接
發(fā)送數(shù)據(jù)給服務(wù)器仅颇，并收集來自服務(wù)器的響應(yīng)數(shù)據(jù)
使用NSURLConnection發(fā)送請(qǐng)求的步驟很簡(jiǎn)單
創(chuàng)建一個(gè)NSURL對(duì)象，設(shè)置請(qǐng)求路徑
傳入NSURL創(chuàng)建一個(gè)NSURLRequest對(duì)象，設(shè)置請(qǐng)求頭和請(qǐng)求體
使用NSURLConnection發(fā)送請(qǐng)求
NSURLConnection常見的發(fā)送請(qǐng)求方法有以下幾種
同步請(qǐng)求
+ (NSData *)sendSynchronousRequest:(NSURLRequest *)request returningResponse:(NSURLResponse **)response error:(NSError **)error;
異步請(qǐng)求：根據(jù)對(duì)服務(wù)器返回?cái)?shù)據(jù)的處理方式的不同溉奕，又可以分為2種
block回調(diào)
+ (void)sendAsynchronousRequest:(NSURLRequest*) request? ? ? ? ? ? ? ? ? ? ? ? ? queue:(NSOperationQueue*) queue? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? completionHandler:(void (^)(NSURLResponse* response, NSData* data, NSError* connectionError)) handler;
代理
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate;
+ (NSURLConnection*)connectionWithRequest:(NSURLRequest *)request delegate:(id)delegate;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:(BOOL)startImmediately;
在startImmediately = NO的情況下，需要調(diào)用start方法開始發(fā)送請(qǐng)求
- (void)start;
成為NSURLConnection的代理忍啤，最好遵守NSURLConnectionDataDelegate協(xié)議
NSURLConnectionDataDelegate協(xié)議中的代理方法
開始接收到服務(wù)器的響應(yīng)時(shí)調(diào)用
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
接收到服務(wù)器返回的數(shù)據(jù)時(shí)調(diào)用（服務(wù)器返回的數(shù)據(jù)比較大時(shí)會(huì)調(diào)用多次）
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;
服務(wù)器返回的數(shù)據(jù)完全接收完畢后調(diào)用
- (void)connectionDidFinishLoading:(NSURLConnection *)connection;
請(qǐng)求出錯(cuò)時(shí)調(diào)用（比如請(qǐng)求超時(shí)）
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
NSMutableURLRequest是NSURLRequest的子類加勤，常用方法有
設(shè)置請(qǐng)求超時(shí)等待時(shí)間（超過這個(gè)時(shí)間就算超時(shí)，請(qǐng)求失斖ā）
- (void)setTimeoutInterval:(NSTimeInterval)seconds;
設(shè)置請(qǐng)求方法（比如GET和POST）
- (void)setHTTPMethod:(NSString *)method;
設(shè)置請(qǐng)求體
- (void)setHTTPBody:(NSData *)data;
設(shè)置請(qǐng)求頭
- (void)setValue:(NSString *)value forHTTPHeaderField:(NSString *)field;
創(chuàng)建GET請(qǐng)求
NSString *urlStr = [@"http://120.25.226.186:32812/login?username=123&pwd=123" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *url = [NSURL URLWithString:urlStr];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
創(chuàng)建POST請(qǐng)求
NSString *urlStr = @"http://120.25.226.186:32812/login";
NSURL *url = [NSURL URLWithString:urlStr];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
request.HTTPMethod = @"POST";
// 請(qǐng)求體
NSString *bodyStr = @"username=123&pwd=123";
request.HTTPBody = [bodyStr dataUsingEncoding:NSUTF8StringEncoding];
