Solidity 编译合约警告 Function state mutability can be restricted to pure

因为下一个项目涉及到 以太坊 合约相关的东西，因此放假的时候需要学习以下 Solidity 相关的东西

刚刚在编译合约的时候出现了以下警告

Warning: Function state mutability can be restricted to pure\n  function  sayHi() public view returns (string memory _greeting){\n  ^ (Relevant source part starts here and spans across multiple lines

修复方法很简单，就是把 public view 改成 public pure

比如我的合约源码如下

pragma solidity ^0.5.8;
contract HelloWorldContract {
  function  sayHi() public view returns (string memory _greeting){
    _greeting = 'Hello World';
  }
}

则需要改成

pragma solidity ^0.5.8;
contract HelloWorldContract {
  function  sayHi() public pure returns (string memory _greeting){
    _greeting = 'Hello World';
  }
}