Getting array of struct from another contract

Question

I have 2 contracts.

contract Contract1{
  struct Data {
      uint data1;
      string data2;
  }
  Data [] newData;
}

Let's assume that I have datas in newData

import "./Contract1.sol";
contract Contract2{
  Data storage newOne = newData[0];
}

I want to reach array of struct which is in Contract1 as above. How can I access to Contract1 from Contract2?

Petr Hejda · Accepted Answer · 2021-04-30 20:20:01Z

1

You can extend a contract with the is keyword.

Child contracts (in your case Contract2) can access all non-private parent (in your case Contract1) properties.

pragma solidity ^0.8;

import "./Contract1.sol";

contract Contract2 is Contract1 {
    function foo() external {
        Data storage newOne = newData[0];
        // newOne.data1 = 1;
        // newOne.data2 = 'hello';
    }
}

Edit: Mind that newData[0] is trying to access index 0 of the array, but when the contract is deployed, the array is empty (does not have index 0). You can create the first item (with index 0 and dummy data) by executing this function:

function add() external {
    newData.push(Data(1, 'a'));
}

edited Apr 30, 2021 at 20:20

answered Apr 30, 2021 at 13:56

Petr Hejda

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2 Comments

almi Over a year ago

I got an type error. Contract "Contract2" should be marked as abstact.

Petr Hejda Over a year ago

@almi That's unrelated to your original question and to the solution. The "should be marked as abstract" error shows up when your contract has a function definition without implementation, e.g. function foo() external; (mind the semicolon at the end and no function body).

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