如何使用Cloud Function .onWrite（Firebase）從其他數據庫節點獲取變量

Question

如果Firebase節點設置為true，我嘗試設置一些變量以發送以傳遞給函數。 我正在嘗試根據以下文檔使用.parent和.val()函數來設置customer_id ： https : .val()

exports.newCloudFunction = functions.database.ref('/user/{userId}/sources/saveSource').onWrite(event => {
// Retrieve true/false value to verify whether card should be kept on file
const saveSource = event.data.val();

if (saveSource) {
  let snap = event.data;
  let customer_id = snap.ref.parent.child('customer_id').val();
  console.log(customer_id);
  // pass customer_id into function
}

我期望snap.ref.parent引用/sources和.child('customer_id').val()從customer_id鍵訪問值。

但是，當我嘗試運行此功能時，出現以下錯誤：

TypeError: snap.ref.parent.child(...).val is not a function
at exports.linkCardToSquareAccount.functions.database.ref.onWrite.event (/user_code/index.js:79:56)
at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:35:20
at process._tickDomainCallback (internal/process/next_tick.js:129:7)

如何引用原始onWrite位置范圍之外的節點？

Answer 1

您不能只在數據庫引用上調用.val()並期望在該位置獲取數據。 您需要添加一個值偵聽器以獲取新數據。

幸運的是，Cloud Functions內部完全支持此功能：

exports.newCloudFunction = functions.database.ref('/user/{userId}/sources/saveSource').onWrite(event => {
    // Retrieve true/false value to verify whether card should be kept on file
    const saveSource = event.data.val();

    if (saveSource) {
        const customerIdRef = event.data.adminRef.parent.child('customer_id')
        // attach a 'once' value listener to get the data at this location only once
        // this returns a promise, so we know the function won't terminate before we have retrieved the customer_id
        return customerIdRef.once('value').then(snap => {
            const customer_id = snap.val();
            console.log(customer_id);
            // use customer_id here
        });
    } 
});

您可以在此處了解更多信息 。