【solidity】继承和调用权限(10)

pragma solidity ^0.4.0;

contract father {
    uint public money = 10000;

    function dahan() pure public returns(string) {
        return "dahan";
    }

}

contract son is father {

    function getMoney() view public returns(uint){
        return money; // 10000
    }

    function test() pure public returns(string) {
        return dahan(); // "dahan"
    }
}

pragma solidity ^0.4.0;

contract grandfather {
    uint public gudong = 200;

    function zhongdi() pure public returns(string){
        return "zhongdi";
    }
}

contract father is grandfather {
    uint public money = 10000;

    function dahan() pure public returns(string) {
        return "dahan";
    }

}

contract son is father {
    function getMoney() view public returns(uint){
        return money;
    }

    function test() pure public returns(string) {
        return dahan();
    }

    function getGudong() view public returns(uint){
        return gudong;
    }

}

pragma solidity ^0.4.0;

contract father {

    uint public money = 10000;

    // uint money = 10000;  不加上任何属性符 可以继承
    // uint internal money = 10000;  可以被继承

    // uint external money = 10000; 不能使用该符号
    // uint private money = 10000; 不能被继承


    // 不加符号，public, internal 可以被继承  external 必须要 this.danhan
    // private 不能被继承
    function dahan() pure public returns(string) {
        return "dahan";
    }

    // public 任何情况都可以调用
    // internal 只能是合约的内部调用 或是 继承合约的内部调用
    // external 只能是合约的外部调用 或是 继承合约的外部调用 
    //          可以用this.danhan() 这种方式在内部调用。因为this表示该合约，也是表示外部调用
    // private 只能是合约自己调用

}

contract son is father {

    function getMoney() view public returns(uint){
        return money;
    }

}

contract externalTest {
    // 创建合约以后，调用方法。 跟继承不一样的方式调用
    father f = new father();

    function externalTestIt() view public returns(string){
        return f.dahan();
    }
}

function getBalance() public view returns (uint) {
    return address(this).balance;
}

function add(uint a, uint b) public pure returns (uint) {
    return a + b;
}