使用afn 上传图片

需要将 图片的转成 NSData数据类型

AFHTTPRequestOperation *op = [manager POST:kAddlist_url
parameters:parameters
constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
//do not put image inside parameters dictionary as I did, but append it!

//这里的name是服务器接收图片的字段。

[formData appendPartWithFileData:imageData name:@"image" fileName:@"file" mimeType:@"image/png"];

} success:^(AFHTTPRequestOperation *operation, id responseObject) {
completion(responseObject);
NSLog(@"Success: %@ ***** %@", operation.responseString, responseObject);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"Error: %@ ***** %@", operation.responseString, error);
}];
[op start];