Solidity : uint256不能隐式转换为uint256[]内存

Question

到目前为止，我已经对数据定位文档进行了RTFM访问，并尝试了这个解决方案，但没有结果。

合同的完整代码如下所示：

pragma solidity ^0.4.13;

contract People {

    Person[] public people;

    struct Person {
        bytes32 firstName;
        bytes32 lastName;
        uint age; 
    }

    function addPerson(bytes32 _firstName, bytes32 _lastName, uint _age) returns (bool success) {

        Person memory newPerson;
        newPerson.firstName = _firstName;
        newPerson.lastName = _lastName;
        newPerson.age = _age;

        people.push(newPerson);
        return true;

    }

    function getPeople() constant returns (bytes32[],bytes32[],uint[]) {

        uint length = people.length;

        bytes32[] memory firstNames = new bytes32[](length);
        bytes32[] memory lastNames = new bytes32[](length);
        uint[] memory ages = new uint[](length);

        for(uint i = 0; i < people.length; i++) {

            // what does <<memory>> do in Solidity?
            Person memory currentPerson;

            currentPerson = people[i];

            firstNames = currentPerson.firstName;
            lastNames = currentPerson.lastName;
            ages = currentPerson.age;
        }

        return (firstNames, lastNames, ages);

    }

}

当我尝试用truffle compile --all编译它时，我得到以下错误：

Compiling ./contracts/ConvertLib.sol...
Compiling ./contracts/MetaCoin.sol...
Compiling ./contracts/Migrations.sol...
Compiling ./contracts/People.sol...

/Users/s.matthew.english/ConsenSys/PegaSys/smart_contracts/peopleList/0.0_peopleList/contracts/People.sol:40:26: TypeError: Type bytes32 is not implicitly convertible to expected type bytes32[] memory.
        firstNames = currentPerson.firstName;
                     ^---------------------^
,/Users/s.matthew.english/ConsenSys/PegaSys/smart_contracts/peopleList/0.0_peopleList/contracts/People.sol:41:25: TypeError: Type bytes32 is not implicitly convertible to expected type bytes32[] memory.
        lastNames = currentPerson.lastName;
                    ^--------------------^
,/Users/s.matthew.english/ConsenSys/PegaSys/smart_contracts/peopleList/0.0_peopleList/contracts/People.sol:42:20: TypeError: Type uint256 is not implicitly convertible to expected type uint256[] memory.
        ages = currentPerson.age;
               ^---------------^
Compiliation failed. See above.

很显然，这与这项任务有关：

        firstNames = currentPerson.firstName;
        lastNames = currentPerson.lastName;
        ages = currentPerson.age;

这有什么问题吗？

为了提供一些上下文，编写此合同是完成本教程的一部分，特别是在~20:26上的合同。

Answer 1

你为什么需要currentPerson呢？以下代码似乎有效：

pragma solidity ^0.4.13;

contract People {

Person[] public people;

struct Person {
    bytes32 firstName;
    bytes32 lastName;
    uint age; 
}

function addPerson(bytes32 _firstName, bytes32 _lastName, uint _age) returns (bool success) {

    Person memory newPerson;
    newPerson.firstName = _firstName;
    newPerson.lastName = _lastName;
    newPerson.age = _age;

    people.push(newPerson);
    return true;

}

function getPeople() constant returns (bytes32[],bytes32[],uint[]) {

    uint length = people.length;

    bytes32[] memory firstNames = new bytes32[](length);
    bytes32[] memory lastNames = new bytes32[](length);
    uint[] memory ages = new uint[](length);

    for(uint i = 0; i < people.length; i++) {

        // what does <<memory>> do in Solidity?
        //Person memory currentPerson;
        //currentPerson = people[i];

        firstNames[i] = people[i].firstName;
        lastNames[i] = people[i].lastName;
        ages[i] = people[i].age;
    }

    return (firstNames, lastNames, ages);

}

}

Answer 2

我给数组分配了一个数组元素，必须这样做：

    firstNames[i] = currentPerson.firstName;
    lastNames[i] = currentPerson.lastName;
    ages[i] = currentPerson.age;