Solidity 编译合约错误 No visibility specified. Did you intend to add "public"

没想到 Solidity 里也有 public 和 private 两种可见修饰符

如果一个方法需要对外可见，也就是可以通过合约 ABI 来访问，那么需要添加 public ，如果不对外访问，则需要添加 private

如果你没添加，则会出现以下错误

HelloWorldContract.sol:3:3: SyntaxError: No visibility specified. Did you intend to add "public"?\n  function sayHi() view returns (string){\n  ^ (Relevant source part starts here and spans across multiple lines).\n

比如我的源码如下

pragma solidity ^0.5.8;
contract HelloWorldContract {
  function  sayHi() pure 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';
  }
}