javascript - 如何将 Promise.all 传递给另一个函数 Cloud Functions for Firebase

Question

我正在尝试从 Firebase 设置一些变量，然后将它们传递给 anotherfunction。目前，Promise.all 正在正确设置 foo 和 bar，但是，我无法判断 foo和 bar 被传递到 then，并且 Firebase 的范围不正确。

Promise.all block 基于此处的教程:https://www.youtube.com/watch?v=NgZIb6Uwpjc&t=305s

exports.someFunction = functions.database.ref(`/data`).onWrite(event => {
  const condition = event.data.val()
  if (condition) {
    // Get the data at this location only once, returns a promise, to ensure retrieval of foo and bar
    const foo = event.data.adminRef.child('foo').once('value')
    const bar = event.data.adminRef.child('bar').once('value')

    return Promise.all([foo, bar]).then(results => {
      const foo = results[0].val()
      const bar = results[1].val()
      // Properly sets foo and bar
      // As far as I can tell foo and bar are not passed into 'then'
    }).then([foo, bar] => {
      return someModule.anotherFunction({
        "foo": foo,
        "bar": bar
      })
    })
  } else {
    console.log('Fail');
  }
});

如何将 foo 和 bar 传递给 anotherFunction 并将该函数的响应设置为 Firebase？

Answer 1

这里是你出错的地方——看代码中的注释

return Promise.all([foo, bar]).then(results => {
  const foo = results[0].val()
  const bar = results[1].val()
  // you dont' return anything so, the following .then gets undefined argument
}).then([foo, bar] => {
  //    ^^^^^^^^^^^^^ invalid syntax, you need .then(([foo, bar]) =>
  return someModule.anotherFunction({
    "foo": foo,
    "bar": bar
  })

为了简化您的代码，只需删除 }).then([foo, bar] => { together!!

return Promise.all([foo, bar])
.then(results => {
    const foo = results[0].val()
    const bar = results[1].val()
    return someModule.anotherFunction({
        "foo": foo,
        "bar": bar
    }))
.then ...

但是，如果实际代码比您显示的更多，您可以这样做

return Promise.all([foo, bar])
.then(results => results.map(result => result.val()))
.then(([foo, bar]) => someModule.anotherFunction({
    "foo": foo,
    "bar": bar
}))
.then ...

或

return Promise.all([foo, bar])
.then(([foo, bar]) => ([foo.val(), bar.val()]))
.then(([foo, bar]) => someModule.anotherFunction({
    "foo": foo,
    "bar": bar
}))
.then ...