Firestore:多个条件where子句

Question

例如,我的书籍列表中有动态过滤器,我可以设置特定的颜色,作者和类别.此过滤器可以一次设置多种颜色和多个类别.

   Book > Red, Blue > Adventure, Detective.

如何有条件地添加"where"？

  firebase
    .firestore()
    .collection("book")
    .where("category", "==", )
    .where("color", "==", )
    .where("author", "==", )

    .orderBy("date")
    .get()
    .then(querySnapshot => {...

Answer 1

正如您在API文档中看到的那样,collection()方法返回一个CollectionReference.CollectionReference扩展了Query. Query.where()和Query.orderBy()也返回Query对象.所以你可以像这样重写你的代码:

var query = firebase.firestore().collection("book")
query = query.where(...)
query = query.where(...)
query = query.where(...)
query = query.orderBy(...)
query.get().then(...)

现在,您可以输入条件来确定要在每个阶段应用哪些过滤器.

Answer 2

Firebase 版本 9

文档没有涵盖这一点，但以下是如何向查询添加条件 where 子句：

import { collection, query, where } from 'firebase/firestore'

const queryConstraints = []
if (group != null) queryConstraints.push(where('group', '==', group))
if (pro != null) queryConstraints.push(where('pro', '==', pro))
const q = query(collection(db, 'videos'), ...queryConstraints)

这个答案的来源是一些直观的猜测。

Answer 3

对于 Firebase 版本 9（2022 年 1 月更新）：

您可以使用多个 where 子句过滤数据：

import { query, collection, where, getDocs } from "firebase/firestore";

const q = query(
  collection(db, "products"),
  where("category", "==", "Computer"),
  where("types", "array-contains", ['Laptop', 'Lenovo', 'Intel']),
  where("price", "<=", 1000),
);

const docsSnap = await getDocs(q);
    
docsSnap.forEach((doc) => {
  console.log(doc.data());
});

Answer 4

除了@Doug Stevenson 的回答。当您拥有多个时，有where必要使其更具活力，就像我的情况一样。

function readDocuments(collection, options = {}) {
    let {where, orderBy, limit} = options;
    let query = firebase.firestore().collection(collection);

    if (where) {
        if (where[0] instanceof Array) {
            // It's an array of array
            for (let w of where) {
                query = query.where(...w);
            }
        } else {
            query = query.where(...where);
        }

    }

    if (orderBy) {
        query = query.orderBy(...orderBy);
    }

    if (limit) {
        query = query.limit(limit);
    }

    return query
            .get()
            .then()
            .catch()
    }

// Usage
// Multiple where
let options = {where: [["category", "==", "someCategory"], ["color", "==", "red"], ["author", "==", "Sam"]], orderBy: ["date", "desc"]};

//OR
// A single where
let options = {where: ["category", "==", "someCategory"]};

let documents = readDocuments("books", options);