iOS - 用POST Request上傳檔案給Server

在UIKit 就有提供功能很強大的class讓我們使用可以自訂HTTP Request的格式
讓我們可以傳送http request給server
接下來我們會用到幾個class
NSURL, NSMutableURLRequest, NSURLConnection
有關HTTP基本的知識，請參考
在iOS 手持式裝置中我們就是要用上面提到的Class來自訂
自已的Post Request並且把file 轉成NSData傳到server，要記得，要傳到遠端的東西都要轉成NSData
先來看看怎麼把file轉成NSData
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NSString * filePath = @"/Users/macuser/Desktop/back.png";
NSData *fileContent = [NSData dataWithContentsOfFile:filePath options:0 error:nil];
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很簡單地利用NSData的 dataWithContentsOfFile:options:error: 這個method把file轉成NSData
在這裡是利用simulator來拿桌面上的file，真正放到iOS裝置上時，要用合法位置的檔案
再來就是自訂POST Request的部分
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-(void) uploadBinary:(NSData * ) binary withURL:(NSString * ) urlAddress withAttName:(NSString *) attname andFilename:(NSString *) filename{
   
    NSURL *theURL = [NSURL URLWithString:urlAddress];
    NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:theURL
                                                              cachePolicy:NSURLRequestReloadIgnoringCacheData
                                                          timeoutInterval:20.0f];
    [theRequest setHTTPMethod:@"POST"];
    NSString *boundary = [[NSProcessInfo processInfo] globallyUniqueString];
    NSString *boundaryString = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
    [theRequest addValue:boundaryString forHTTPHeaderField:@"Content-Type"];
   
    // define boundary separator...
    NSString *boundarySeparator = [NSString stringWithFormat:@"--%@\r\n", boundary];
   
    //adding the body...
    NSMutableData *postBody = [NSMutableData data];

    [postBody appendData:[boundarySeparator dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"%@\"\r\n",attname, filename] dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:[@"Content-Type: application/octet-stream\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    [postBody appendData:binary];
   
    [postBody appendData:[[NSString stringWithFormat:@"\r\n--%@--\r \n",boundary]
                          dataUsingEncoding:NSUTF8StringEncoding]];
    [theRequest setHTTPBody:postBody];   
   
   
    [[[NSURLConnection alloc] initWithRequest:theRequest delegate:self] autorelease];
}
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綠色的部分是Header，藍色的部分是Post body，其中boundary的部分都不能省略
  [theRequest setHTTPMethod:@"POST"];是設定POST Method
NSString *boundaryString = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary]; 
[theRequest addValue:boundaryString forHTTPHeaderField:@"Content-Type"];設定 Type

整個BODY都要用NSData傳出去，所以要宣告一個NSMutableData
@"Content-Disposition: form-data; name=\"%@\"; filename=\"%@\"\r\n",attname, filename
這一串是和Server說，POST的Key要叫做attname，這個file的名字要放在 filename(上列右邊)這個變數而server是用"filename"這個key把filename的值取出來