如何避免使用firebase事务嵌套承诺？

Question

在 onDelete 触发器中，我正在运行一个事务来更新某个对象。我现在需要在运行该事务之前进行一些清理并删除一些其他对象。添加清理代码后，我收到关于嵌套承诺的警告，我不知道如何摆脱。这是一个sn-p：

exports.onDeleteAccount = functions.firestore
.document('accounts/{accountID}')
.onDelete((account, context) => {
  // First do the cleanup and delete addresses of the account
  const query = admin.firestore().collection('account_addresses').where('accountID', '==', account.id);
  return query.get().then(addresses => {
    var promises = [];
    addresses.forEach(address=>{
      promises.push(address.ref.delete());
    })
    return Promise.all(promises);
  }).then(()=> {
    // Then run the transaction to update the account_type object
    return runTransaction(transaction => {
      // This code may get re-run multiple times if there are conflicts.
      const acc_type = account.data().type;
      const accountTypeRef = admin.firestore().doc("account_types/"+acc_type);
      return transaction.get(accountTypeRef).then(accTypeDoc => {
        // Do some stuff and update an object called users
        transaction.update(accountTypeRef, {users: users});
        return;          
      })
    })
  })
  .catch(error => {
    console.log("AccountType delete transaction failed. Error: "+error);
  });
})

Answer 1

我认为问题不是来自Transaction，而是来自您调用delete() 的forEach 循环。您应该使用Promise.all() 来返回一个在传递给promises 数组的所有承诺（由delete() 返回）都已履行时履行的单一承诺，见下文。

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另外，你做runTransaction(transaction => {...}) 但runTransaction 是Firestore 的一个方法。你应该这样做admin.firestore().runTransaction(...)。

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因此，以下应该可以解决问题：

exports.onDeleteAccount = functions.firestore
    .document('accounts/{accountID}')
    .onDelete((account, context) => {
        // First do the cleanup and delete addresses of the account
        const query = admin.firestore().collection('account_addresses').where('accountID', '==', account.id);
        return query.get()
            .then(addresses => {
                const promises = [];
                addresses.forEach(address => {
                    promises.push(address.ref.delete());
                })
                return Promise.all(promises);
            }).then(() => {
                // Then run the transaction to update the account_type object
                return admin.firestore().runTransaction(transaction => {
                    // This code may get re-run multiple times if there are conflicts.
                    const acc_type = account.data().type;
                    const accountTypeRef = admin.firestore().doc("account_types/" + acc_type);
                    return transaction.get(accountTypeRef).then(accTypeDoc => {
                        // Do some stuff and update an object called users
                        transaction.update(accountTypeRef, { users: users }); 
                    })
                })
            })
            .catch(error => {
                console.log("AccountType delete transaction failed. Error: " + error);
            });
    })