Importing Solidity Contracts

One great feature of Solidity is the ability to import contracts into other contracts.

Let’s take the previous contract and split it up into two separate files:

Ownable.sol Token.sol

Create these two files in Remix and copy the following content into the files:

//SPDX-License-Identifier: MIT
 
pragma solidity ^0.8.10;
 
contract Owned {
    address owner;
 
    constructor() {
        owner = msg.sender;
    }
 
    modifier onlyOwner() {
        require(msg.sender == owner, "You are not allowed");
        _;
    }
}

Let’s test this and head over to the Run Tab. You will see again several contracts in the dropdown.

If you select “Token” from the dropdown and deploy it, you’ll get the same contract as in the beginning, but better:

1. The Contracts are split up into smaller logical units
2. With modifiers we have re-usable small components we can also use in contracts extending the base contract
3. With separate files we created a better organization of code

Now, let’s have a look what happens here behind the scenes!