Firestore：多个条件where子句 [英] Firestore: Multiple conditional where clauses

问题描述

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。
此过滤器可以同时设置多种颜色和多个类别。

For example I have dynamic filter for my list of books where I can set specific color, authors and categories. This filter can set multiple colors at once and multiple categories.

   Book > Red, Blue > Adventure, Detective.

如何有条件地添加where？

How can I add "where" conditionally?

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

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

推荐答案

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

As you can see in the API docs, the collection() method returns a CollectionReference. CollectionReference extends Query. Query.where() and Query.orderBy() also return Query objects. So you can rewrite your code like this:

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

现在你可以放入条件来确定你想在每个阶段应用哪些过滤器。

Now you can put in conditionals to figure out which filters you want to apply at each stage.

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