ASIFormDataRequest的使用——上传下载

向服务器端上传数据是使用ASIFormDataRequest ，模拟 Form表单提交，其提交格式与 Header会自动识别。

没有文件：application/x-www-form-urlencoded 

有文件：multipart/form-data

// 实例化
ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
// 设置参数，即类似于Form表单
[request setPostValue:@"Ben" forKey:@"first_name"];
[request setPostValue:@"Copsey" forKey:@"last_name"];
[request setFile:@"/Users/ben/Desktop/ben.jpg" forKey:@"photo"];
[request addData:imageData withFileName:@"george.jpg" andContentType:@"image/jpeg" forKey:@"photos"];
// 如果要发送自定义数据：
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request appendPostData:[@"This is my data"dataUsingEncoding:NSUTF8StringEncoding]];
// Default becomes POST when you use appendPostData: /appendPostDataFromFile: / setPostBody:
[request setRequestMethod:@"PUT"];