Objective-c - AFNetworking3.0 post request base64 encoding is transmitted to the background with an extra = sign at the beginning

Question

The AFNetworking3.0 framework is used to make a post request on the client, and the request parameters are base64 encoded.
But something very strange is: after posting, I captured the packet and found that there was an extra "=" sign in front of the entire request body, which caused the backend to not recognize it correctly.

This is the content seen through packet capture, and the "=" sign appears

This is the result of my client using GTM encryption, without the "=" sign in front

I don’t know if it’s a problem with the AF version. I haven’t tested it yet. Do you have any friends who have encountered the same situation?

更新一下：反复研究过后，发现是我post的时候使用的是string（base64编码后），但是afnetworking在运行中，会以键值对的形式：key=value 传过去。因为这个多余的"="号就是这个键值对中残留的（这里显示key为空）。所以我现在从这个方面着手解决。