Question

我部署了两份合同，一份是Callee，另一份是Caller。调用者使用Callee提供的功能。函数调用直接调用Callee是成功的，但是，调用者不起作用。实际上，我从互联网上尝试了不同的案例，但都没有。我是否会错过一些棘手的事情？以下是源代码：

Callee.sol

pragma solidity ^0.4.6;

contract Callee {
    uint[] public values;

    function getValue(uint initial) public pure returns(uint) {
        return initial + 150;
    }
    function storeValue(uint value) public {
        values.push(value);
    }
    function getValues() public view returns(uint) {
        return values.length;
    }
}

Caller.sol

pragma solidity ^0.4.6;

contract Caller {
    function someAction(address addr) public returns(uint) {
        Callee c = Callee(addr);
        return c.getValue(100);
    }

    function storeAction(address addr) public returns(uint) {
        Callee c = Callee(addr);
        c.storeValue(100);
        return c.getValues();
    }

    function someUnsafeAction(address addr) public returns(bool){
        return addr.call(bytes4(keccak256("storeValue(uint256)")), 100);
    }
}

contract Callee {
    function getValue(uint initialValue) public returns(uint);
    function storeValue(uint value) public;
    function getValues() public returns(uint);
}

Answer 1

Caller在技术上有效，但没有做到你期待的事情。

问题是Caller.someAction未标有pure或view修饰符，因此您的函数调用会触发新事务。事务调用不能返回值（它编译并运行，但不返回任何内容）。

如果您将Caller.someAction更改为pure功能（并且还要将界面中的Callee.getValue更改为pure以匹配合同），您将获得预期的250返回。

pragma solidity ^0.4.6;

contract Caller {
  function someAction(address addr) public pure returns(uint) {
    Callee  c = Callee(addr);
    return c.getValue(100);
  }

  function storeAction(address addr) public returns(uint) {
    Callee c = Callee(addr);
    c.storeValue(100);
    return c.getValues();
  }

  function someUnsafeAction(address addr) public returns(bool){
    return addr.call(bytes4(keccak256("storeValue(uint256)")), 100);
  }
}

contract Callee {
  function getValue(uint initialValue) public pure returns(uint);
  function storeValue(uint value) public;
  function getValues() public returns(uint);
}

在终端：

$ truffle migrate --reset
Compiling .\contracts\Callee.sol...
Compiling .\contracts\SimpleContract.sol...
Writing artifacts to .\build\contracts

Using network 'development'.

Running migration: 1_initial_migration.js
  Replacing Migrations...
  ... 0x58a14c93acc733bb08e4bb56978d0bb466f8aca7659673426d989ee7e0e626f3
  Migrations: 0x69ed5e4d6172639ed7d3c456ea8b2f2562c7dbcd
Saving successful migration to network...
  ... 0x9a3831076748cc6179ef3e4b3e466c3a4a871e196376bc22c984e91e95fdc567
Saving artifacts...
Running migration: 2_deploy_contracts.js
  Replacing Caller...
  ... 0x7be6840c86a356decacc13967d50ef4fea30e86d30d69b19fb9998ce500c95e8
  Caller: 0xb8c5e079af71813acac73bff9ca8e9e068660e86
  Replacing Callee...
  ... 0xba7f588f9119e67968a7d6ab0110d79e1ecd3003e10cce3134018d42e966c8be
  Callee: 0xd5c110c2f6566fd56749ec1a11328405f9935385
Saving successful migration to network...
  ... 0xc1526876e365189be1529a0943042e3a25e395a5cc19930ad907a694165104f1
Saving artifacts...

$ truffle console
truffle(development)> var caller = Caller.at('0xb8c5e079af71813acac73bff9ca8e9e068660e86');
undefined
truffle(development)> caller.someAction('0xd5c110c2f6566fd56749ec1a11328405f9935385');
{ [String: '250'] s: 1, e: 2, c: [ 250 ] }

智能合约之间的互动无效

1 个答案: