iOS上传文件参数解析(HTTP header Content-Disposition)

AFNetworking中提供的图片上传方法：

[_sessionManager POST:uploadUrl parameters:dict constructingBodyWithBlock:^(id<AFMultipartFormData>  _Nonnull formData) {
if (imageData) {
[formData appendPartWithFileData:imageData name:<#name#> fileName:<#fileName#> mimeType:@"jpg"];
}
} success:^(NSURLSessionDataTask * _Nonnull task, id  _Nonnull responseObject) {
suc(task,responseObject);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
fail(task,error);
}];

可以看到里边有几个字段：

/**
Appends the HTTP header `Content-Disposition: file; filename=#{filename}; name=#{name}"` and `Content-Type: #{mimeType}`, followed by the encoded file data and the multipart form boundary.

@param data The data to be encoded and appended to the form data.
@param name The name to be associated with the specified data. This parameter must not be `nil`.
@param fileName The filename to be associated with the specified data. This parameter must not be `nil`.
@param mimeType The MIME type of the specified data. (For example, the MIME type for a JPEG image is image/jpeg.) For a list of valid MIME types, see http://www.iana.org/assignments/media-types/. This parameter must not be `nil`.
*/
- (void)appendPartWithFileData:(NSData *)data
name:(NSString *)name
fileName:(NSString *)fileName
mimeType:(NSString *)mimeType
{
NSParameterAssert(name);
NSParameterAssert(fileName);
NSParameterAssert(mimeType);

NSMutableDictionary *mutableHeaders = [NSMutableDictionary dictionary];
[mutableHeaders setValue:[NSString stringWithFormat:@"form-data; name=\"%@\"; filename=\"%@\"", name, fileName] forKey:@"Content-Disposition"];
[mutableHeaders setValue:mimeType forKey:@"Content-Type"];

[self appendPartWithHeaders:mutableHeaders body:data];
}