无法在测试期间从智能契约中检索数据

Question

我正在为我的智能合同坚实版0.4.24编写松露测试。这些测试正在释放事件，以便通过智能契约将数据写入内存。但我无法从函数中检索数据。

以下是我的智能合同功能：

previousFarmId = 0；

struct Location {
        string latitude;
        string longitude;
        string locationAddress;
    }

    struct Farm {
        uint farmId;
        string farmName;
        Location location;
    }

mapping (uint => Farm) farms;

function registerFarm(string _farmName, string _farmLatitude, string _farmLongitude, string _locationAddress) public {

        previousFarmId = previousFarmId + 1;

        Location memory newLocation = farmLocation[previousFarmId];
        newLocation.latitude = _farmLatitude;
        newLocation.longitude = _farmLongitude;
        newLocation.locationAddress = _locationAddress;

        Farm memory newFarm = farms[previousFarmId];
        newFarm.farmId = previousFarmId;
        newFarm.farmName = _farmName;
        newFarm.location = newLocation;

        emit FarmRegistered(previousFarmId);

    }

    function getFarmInfo(uint _farmId) public view 
    returns (uint farmId, string farmName, string latitude, string longitude, string locationAddress) {
        Farm memory returnFarm = farms[_farmId];
        farmId = returnFarm.farmId;
        farmName = returnFarm.farmName;
        latitude = returnFarm.location.latitude;
        longitude = returnFarm.location.longitude;
        locationAddress = returnFarm.location.locationAddress;
    }

下面是松露测试：

const farmID = 1；

it("Testing smart contract function harvestGrapes() that allows producer to harvest grapes", async() => {

        const supplyChain = await SupplyChain.deployed();

        await supplyChain.addProducer(producerID, {from: deployerID});

        await supplyChain.registerFarm(farmName, farmLatitude, farmLongitude, farmAddress, {from: producerID});

        const resultFarms = await supplyChain.getFarmInfo.call(farmID);

        console.log('Farm ID: ' + resultFarms[0]);
        console.log('Farm Name: ' + resultFarms[1]);
        console.log('Farm Latitude: ' + resultFarms[2]);
        console.log('Farm Longitude: ' + resultFarms[3]);
        console.log('Farm Address: ' + resultFarms[4]); 
}

控制台日志：

Farm ID: 0
Farm Name:
Farm Latitude:
Farm Longitude:
Farm Address:

测试期间发出的事件：

   ProducerAdded(account: <indexed>)
    FarmRegistered(farmId: 1)
    GrapesHarvested(grapesId: 1)

Answer 1

这部分做不到你想做的。

function registerFarm(string _farmName, string _farmLatitude, string _farmLongitude, string _locationAddress) public {

        previousFarmId = previousFarmId + 1;

        Location memory newLocation = farmLocation[previousFarmId];
        newLocation.latitude = _farmLatitude;
        newLocation.longitude = _farmLongitude;
        newLocation.locationAddress = _locationAddress;

        Farm memory newFarm = farms[previousFarmId];
        newFarm.farmId = previousFarmId;
        newFarm.farmName = _farmName;
        newFarm.location = newLocation;

        emit FarmRegistered(previousFarmId);

    }

首先，将函数参数分配给memory变量newLocation。然后，将参数分配给另一个memory变量newFarm。他们都是memory，所以他们不会坚持。

考虑：

function registerFarm(string _farmName, string _farmLatitude, string _farmLongitude, string _locationAddress) public {

        previousFarmId = previousFarmId + 1;

        Location storage newLocation = farmLocation[previousFarmId];
        newLocation.latitude = _farmLatitude;
        newLocation.longitude = _farmLongitude;
        newLocation.locationAddress = _locationAddress;

        emit FarmRegistered(previousFarmId);

    }

newLocation是一个存储指针，所以分配给它直接到存储。函数执行完毕后，存储将保持不变。当memory变量的函数或函数作用域(新编译器进一步缩小作用域)结束时，它们将被熄灭。

在进入单元测试之前，您可能会发现Remix在进行表面测试和手动测试时非常方便。

希望能帮上忙。