Let's say contract A does not know the address of contract C but it knows what function of C it wants to call. Contract B stores contracts's C address. Therefore contract A wants to request a call to C's function but at the address of contract B. Furthermore, the function returns a value about which contract A cares. Essentially, contract C is a library that contract A wants to use for his own computations but does not know the libraries' address.
Now, I have looked into various ways of doing this with call, delegatecall and fallback function but I think it might not be possible to do it exactly like that.
For example, there was once suggested solution here which I hope is fine to copy here for convenience:
contract Relay {
address public currentVersion;
address public owner;
function Relay(address initAddr){
currentVersion = initAddr;
owner = msg.sender;
}
function(){
if(!currentVersion.delegatecall(msg.data)) throw;
}
Solution 1: I have tried something like the above code, making my contract B to have a fallback function. However, when A executed a call to C through it then it returned me some strange result back to A which made me believe that it will just not work this way for some reason; the result of C will not return through fallback back to A.
Solution 2: The closest I got it to work is when I had A execute a delegatecall to B which in turn executes the delegatecall to C. This meant that C was executing in the context of A and so when I set a storage variable in C, I am actually setting a storage variable in A. Then I had the result of the computation stored in a state variable in A which is not bad. However, this solution also means that B needs to have hardcoded all the variables/logic in the fallback function and cannot access its storage variables because it executes in the context of A. It cannot have the address of C stored in a state variable like the currentVersion in the example above.
I am not sure if everything what I wrote is correct but this is my take on it. I am hoping that maybe solution 1 should still be possible but I did something wrong? Am I missing something?
