Contract Structure & Versions

Code License

  • Specify a license at the top of every file.

// SPDX-License-Identifier: MIT

Solidity Versions

pragma solidity 0.8.7;              // A specific version
pragma solidity ^0.8.7;             // Version 0.8.7 or higher
pragma solidity >=0.8.7 <0.9.0;     // Only versions including or greater than 0.8.7 
                                    // and less than 0.9.0

Contract Template

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract HelloWorld {
}

Import

  • When you have multiple files and you want to import one file into another, Solidity uses the importkeyword:

import "./someothercontract.sol";

contract newContract is SomeOtherContract {
}

  • So if we had a file named someothercontract.sol in the same directory as this contract (that's what the ./means), it would get imported by the compiler.

Contract Layout

  • license

  • version

  • imports

  • errors

  • interfaces, libraries, contracts

  • type declarations

  • state variables

  • events

  • modifiers

  • functions

Function Layout

  • constructor

  • receive function (if exists)

  • fallback function (if exists)

  • external

  • public

  • internal

  • private

  • view & pure functions

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