开发身份证验证功能时，要求以formData形式将身份证正反面图片上传到服务器，实现部分代码如下：
AFHTTPSessionManager *imageManager = [AFHTTPSessionManager manager];
imageManager.responseSerializer = [AFHTTPResponseSerializer serializer];
//url为身份证上传到服务器的完整地址
[imageManager POST:url parameters:nil headers:nil constructingBodyWithBlock:^(id<AFMultipartFormData> _Nonnull formData) {
//上传身份证图片
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.dateFormat = @"yyyyMMddHHmmss";
NSString *str = [formatter stringFromDate:[NSDate date]];
NSString *fileName = [NSString stringWithFormat:@"%@.jpg", str];
//将身份证正反面图片的二进制文件拼在一起(name后面的value一定要跟后台给的接口文档的key一致)
//idCardFrontImg、idCardbackImg为身份证正/反面图片，UIImage类型
[formData appendPartWithFileData:UIImageJPEGRepresentation(idCardFrontImg, 0.5) name:@"frontFile" fileName:fileName mimeType:@"image/jpeg"];
[formData appendPartWithFileData:UIImageJPEGRepresentation(idCardbackImg, 0.5) name:@"backFile" fileName:fileName mimeType:@"image/jpeg"];
} progress:^(NSProgress * _Nonnull uploadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
//上传成功
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
//上传失败
}];
