iOS網絡篇－URLConnection基本使用

知識點
1.HTTP協議的簡介（見上節）
2.URLConnection同步請求
3.URLConnection異步請求
4.URLConnection異步請求Block版本
5.URLConnectionPOST請求
6.URLConnection的封裝

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2.NSURL，用OC中用來表示URL的類
創建URL：

[NSURL URLWithString:urlStr];

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3.NSURLRequest，用來表示一個請求

//創建Request：
        [NSURLRequest requestWithURL:url];
//創建帶超時的Request
        [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:0.01f];

//創建可變的Request，可修改Request的屬性，如Method等，POST用到
        NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
        request.HTTPMethod = @"POST";

//設置請求體
        NSString *paramStr = @"username=qf1508&password=123456";
     request.HTTPBody = [paramStr dataUsingEncoding:NSUTF8StringEncoding];

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4.NSURLConnection，表示一個請求響應的連接

//發送同步請求
        [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

//發送異步請求
        [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {}];

//發送異步請求，delegate版本
        [NSURLConnection connectionWithRequest:request delegate:self];

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4.NSURLConnection的Delegate回調函數

//接收到服務器的響應
        - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;

//接收到服務器發送過來的數據，數據是分段發給我們的，所以這個方法會被調用多次
        - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;

//服務器所有的數據都發送完成之後，會調用這個方法
        - (void)connectionDidFinishLoading:(NSURLConnection *)connection;

//請求失敗(url不合法、超時、網絡中斷等等)時會調用這個方法
        - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;

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:ios9.0不支持http ,推薦https
1接口是https
2修改info.plist

<key>NSAppTransportSecurity</key>
    <dict>
        <key>NSAllowsArbitraryLoads</key>
        <true/>
    </dict>