casting with a parent

[reza-mousapour]

There is a cast(name A for example) that I have and I know its hash. I want to cast another cast(name B) and I want A to be B's parent. I tried post_cast() but I couldn't figure out how should I give the parent field true information. I have tried: parent = hash_of _A parent = A(the ApiCast type) but none of them seemed to work. what is true format for doing this task? can you give me an example? I would appreciate it.