Solana: How to call up an anchor program that has a pda using cpi

**Calling an Anchor Program with a PDA in Solana using C++

Anchor programs are crucial components of the Solana ecosystem, allowing for decentralized, self-executing contracts. In this article, we’ll explore how to call an anchor program from another program on Solana, specifically when the called program has its own PDA (Program Data Area). We’ll cover both the prelude and main parts of the code.

Prerequisites

Before diving into the example, make sure you have a basic understanding of Solana, Anchor programs, and C++. You should also have a Solana CLI setup on your machine. For this example, we’ll be using the Solana CLI to interact with our Anchor program and the solana-program library.

Anchor Program A: Initializing PDA

Anchor program A (A) has an initialize function that initializes its own PDA:

pragma solidity ^0.8.0;


import "

import "


contract AnchorProgramA {

    // Initialize PDA

    function initializePda() public {

        // Create a new SafeERC20 instance and set the base URI

        uint256 _baseUri = 0x5cC7bDf9a1d1F5e8E39f7e24c3AeBf6e1b34e78a4a2ef2a0f7df;

        

        // Create a new SafeERC20 instance with the base URI

        SafeERC20 _pda = SafeERC20(_baseUri);

    }

}

Anchor Program B: Calling A’s Initialize Function

Anchor program B (B) wants to call A‘s initialize function. We’ll create an anchor program that calls A and then returns control back to the caller.

pragma solidity ^0.8.0;


import "

import "


contract AnchorProgramB {

    // Call A's initialize function and get the PDA

    function callA() public {

        // Call A's initialize function

        AnchorProgramA(A).initializePda();

        

        // Get the PDA from A

        uint256 _pda = solana_program.decode_pda(A);

    }

}

Solving for B

To get B back to call the called program, we need a way to interact with it. We can use the solana-program library to create an anchor program that can call another one.

pragma solidity ^0.8.0;


import "

import "

import "


contract SolanaAnchor {

    // Call A's initialize function and get the PDA

    function callA() public {

        AnchorProgramA(A).initializePda();

        

        uint256 _pda = solana_program.decode_pda(A);

    }

}

Getting B Back to Call A

To get B back to call A, we need a way for it to interact with the Solana anchor program. We can use the solana-program library to create an anchor program that calls another one.

pragma solidity ^0.8.0;


import "

import "

import "


contract SolanaProgram {

    // Call B's initialize function and get the PDA

    function callB() public {

        AnchorProgramB(B).callA();

    }

}

Example

Here’s an example of how SolanaAnchor and SolanaProgram could be used in a more complex scenario:

“`solidity

pragma solidity ^0.8.0;

import “

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