How can I invoke the SPL Token program from my program?

Question

I'd like to make custom token program which just proxies all transaction to TOKEN_PROGRAM. I've made custom TOKEN_PROGRAM and ASSOCIATIED_TOKEN_PROGRAM, and what I'm trying to achieve is to make that token_program to invoke existing TOKEN_PROGRAM.

For instance, When I try to invoke token program for transfer, It just simply invokes existing TOKEN_PROGRAM to transfer.

This is what I tried:

                let account_info_iter = &mut accounts.iter();

                let source_account_info = next_account_info(account_info_iter)?;
                let test1 = source_account_info.clone();
                let destination_account_info = next_account_info(account_info_iter)?;
                let test2 = destination_account_info.clone();
                let authority_info = next_account_info(account_info_iter)?;
        
                let transfer_tokens_instruction = transfer(
                    &program_id,
                    &source_account_info.key,
                    &destination_account_info.key,
                    &authority_info.key,
                    &[&source_account_info.key],
                    amount,
                )?;
                let required_accounts_for_transfer = [
                    test1,
                    test2,
                ];
                
                invoke(
                    &transfer_tokens_instruction,
                    &required_accounts_for_transfer,
                )?;

But it just simply don't work. How do I invoke token program? is there any source I can see?

Answer 1

Use the anchor_spl crate.

This source code uses that crate to accomplish exactly what I believe you're trying to do, hope it helps you:

https://github.com/coral-xyz/anchor/blob/master/tests/spl/token-proxy/programs/token-proxy/src/lib.rs

Answer 2

check this detailed and very helpful article on Cross Program Invocation.

https://blocksecteam.medium.com/secure-the-solana-ecosystem-2-calling-between-programs-5fa3d947c4ed