javascript - Firebase.firestore() 不是函数？

Question

我们正在尝试转换此 json 对象时间戳：

Object {
  "_nanoseconds": 725000000,
  "_seconds": 1621386976,
}

到firebase时间戳：

t {
  "nanoseconds": 725000000,
  "seconds": 1621386976,
}

我们抛出错误的代码：

const lastItemIndex = thoughts.length - 1;
console.log(thoughts[lastItemIndex].date_created); // <--- logs Object timestamp

const seconds = thoughts[lastItemIndex].date_created._seconds;
console.log(seconds); // <--- logs seconds

const nanoseconds = thoughts[lastItemIndex].date_created._nanoseconds;
console.log(nanoseconds); // <---- logs nanoseconds

const lastDate = Firebase.firestore().Timestamp(seconds, nanoseconds); // <--- error
console.log(lastDate);

我们在我们的文件中导入 Firebase，如下所示：

import Firebase from '../../firebase';

在 firebase.js 文件中：

import * as firebase from 'firebase/app';

// Optionally import the services that you want to use
import 'firebase/firestore';

我们得到的警告：

[Unhandled promise rejection: TypeError: _firebase.default.firestore().Timestamp is not a function. (In '_firebase.default.firestore().Timestamp(seconds, nanoseconds)', '_firebase.default.firestore().Timestamp' is undefined)]

我们还尝试了以下方法：

const lastDate = new Firebase.firestore.Timestamp(seconds, nanoseconds);

并得到以下错误：

[Unhandled promise rejection: TypeError: undefined is not a constructor (evaluating 'new _firebase.default.firestore.Timestamp(seconds, nanoseconds)')]

我们遵循文档无济于事。我们如何正确转换它？

编辑

同时导出 Time_stamp 和 Firebase 会破坏应用程序 [应用程序的其余部分无法识别 Firebase 导出]

export default Firebase让一切恢复正常。但是转换时间戳的问题仍然存在

// Initialize Firebase

export const Firebase = firebase.initializeApp(firebaseConfig);
export const Time_stamp = firebase.firestore.Timestamp();

// export default Firebase;

标签： javascriptfirebasegoogle-cloud-firestore

Answer 1

问题在于您如何导入和导出库。

审查您的代码

如果这是您从主库导入的位置，您还需要确保正确导出它。查看您当前的firebase.js文件：

import * as firebase from 'firebase/app';

// Optionally import the services that you want to use
import 'firebase/firestore';

/* ... */

// Initialize Firebase

const Firebase = firebase.initializeApp(firebaseConfig);

export default Firebase; // <- this is a firebase.app.App not firebase itself

您正在导出一个实例firebase.app.App而不是firebase（整个 firebase 库和命名空间）。

当您拥有一个firebase.app.App实例时，您可以使用app.firestore(). 因为您像Firebase在主代码中一样导入此应用程序实例，所以您会将其与firebase.firestore()执行其他操作的普通程序混淆。

为了帮助说明差异，请看一下：

import * as firebase from "firebase/app";
import "firebase/firestore";

const config = { /* ... */ };

const defaultFirebaseApp = firebase.initializeApp(config);

// the instance of Firestore for the default app
const dbApp = defaultFirebaseApp.firestore();

// the instance of Firestore for the default app
const dbDefault = firebase.firestore();
// OR
// const dbDefault = firebase.firestore(dbApp);

console.log(dbApp === dbDefault); // -> true

const namedFirebaseApp = firebase.initializeApp(config, "something");

const dbNamedApp = namedFirebaseApp.firestore(); // returns instance of Firestore for the named app
// OR
// const dbNamedApp = firebase.firestore(dbNamedApp);

console.log(dbDefault === dbNamedApp); // -> false

推荐的出口风格

要从中正确导出 Firebase 库firebase.js，您需要（并且应该）使用：

import firebase from 'firebase/app';
import 'firebase/firestore';

/* ... */

// Initialize Firebase

firebase.initializeApp(firebaseConfig);

export default firebase; // re-export firebase library & namespace

通过以这种方式重新导出库，您可以像遇到的所有代码示例一样使用它：

import firebase from '../../firebase';

const {_nanoseconds, _seconds} = thoughts[lastItemIndex].date_created;
const dateCreatedAsTimestamp = new firebase.firestore.Timestamp(_nanoseconds, _seconds);

const db = firebase.firestore();

db.doc("collection/doc")
  .set({
    date_created: dateCreatedAsTimestamp
  })
  .then(
    () => console.log("success"),
    (err) => console.error("failed", err);
  );

替代导出样式

如果您打算向 中添加一些实用功能firebase.js，则导入内容的方式会略有变化

import firebase from 'firebase/app';
import 'firebase/firestore';

/* ... */

// Initialize Firebase

export const defaultApp = firebase.initializeApp(firebaseConfig);

export function castToTimestamp(timestampLikeObject) {
  const {_nanoseconds, _seconds} = timestampLikeObject;
  return new firebase.firestore.Timestamp(_nanoseconds, _seconds);
}

export default firebase; // re-export firebase library & namespace as the default

使用上述文件，您可以将其导入为：

// you can import this normally like in the other example, but we'll
// include some of the other exports (like the utility function)
import firebase, { castToTimestamp } from '../../firebase';

const {_nanoseconds, _seconds} = thoughts[lastItemIndex].date_created;
const dateCreatedAsTimestamp = new firebase.firestore.Timestamp(_nanoseconds, _seconds);
// OR
// const dateCreatedAsTimestamp = castToTimestamp(thoughts[lastItemIndex].date_created);

const db = firebase.firestore();

db.doc("collection/doc")
  .set({
    date_created: dateCreatedAsTimestamp
  })
  .then(
    () => console.log("success"),
    (err) => console.error("failed", err);
  );