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solidity | 关键词 virtual、override、super

 2 years ago
source link: https://benpaodewoniu.github.io/2023/02/19/solidity59/
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solidity | 关键词 virtual、override、super

virtual 和 override 相当于重写父类的方法，作用和 java 的一样。

  • virtual
    • 父合约中的函数，如果希望子合约重写，需要加上 virtual 关键字。
  • override
    • 子合约重写了父合约中的函数，需要加上 override 关键字。

注意：用 override 修饰 public 变量，会重写与变量同名的 getter 函数，例如：

mapping(address => uint256) public override balanceOf;
pragma solidity ^0.8.0;

contract A{

string public name;
    string public t;
    uint256 public c;
    function test() public{
        pre();
        c = c + 1;
    }

function pre() internal virtual{
        t = "test";
    }
}

contract Test is A {

function pre() internal override{
        name = "test";
    }
}

部署 Test 合约，部署完成，调用变量

  • C
    • 0
  • name
    • ""
  • t
    • ""

调用 test 函数，这几个值变为

  • C
    • 1
  • name
    • test
  • t
    • ""

说明，重写方法后，父函数就不再执行。如果想要执行父方法，可以使用 super。

pragma solidity ^0.8.0;

contract A{

string public name;
    string public t;
    uint256 public c;
    function test() public{
        pre();
        c = c + 1;
    }

function pre() internal virtual{
        t = "test";
    }
}

contract Test is A {

function pre() internal override{
        super.pre();
        name = "test";
    }
}
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