Firebase Firestore 获取集合中每个文档的子集合答案

【问题标题】：Firebase Firestore Get Subcollections for each document in a collectionFirebase Firestore 获取集合中每个文档的子集合
【发布时间】：2019-02-15 11:55:56
【问题描述】：

我的数据库有一个部分的集合，每个部分都包含一个子部分的子集合。

这是我需要创建的数组：

[
  {
    "sectiontitle": "first section",
    "sectiontype": "1",
    "__id__": "6jwwukHmOs1743yC13vH",
    "subsections": [
      {
        "desc": "blah blah blah",
        "__id__": "KTq4MJTEMbDfR33RoX9J"
      },
      {
        "desc": "blah blah blah",
        "__id__": "ASFSADFSAFSADFSADFFS"
      }
    ]
  },
  {
    "sectiontitle": "second section",
    "sectiontype": "1",
    "__id__": "5jwwDHEDOs1743yC13vG",
    "subsections": [
      {
        "desc": "blah blah blah",
        "__id__": "DFG4MJTEMbDfR33DDDDD"
      },
      {
        "desc": "blah blah blah",
        "__id__": "ASDFGHFSAFSADFSHJFRD"
      }
    ]
  }
]

我的代码是：

    // get sections
    firebase.firestore().collection("sections").get().then((sections) => {
      var myarray = [];
      var i = 0;
      sections.forEach((section) => {
        var sectiondata = section.data();
        sectiondata.__id__ = section.id
        sectiondata.subsections = [];
        myarray.push(sectiondata);

        //get subsections
        firebase.firestore().collection("sections").doc(sectiondata.__id__).collection("subsections").get().then((subsections) => {
          subsections.forEach((subsection) => {
            var subsectiondata = subsection.data();
            subsectiondata.__id__ = subsection.id;
            myarray.push('sections.' + i + '.subsections', subsectiondata); // problem is i index is not correct
          });
        });

        i++;

      });
    });

这个问题是i 索引不正确，因为读取的部分已经完成并在开始读取子部分时循环通过foreach。我不熟悉 Javascript 承诺，所以我希望有人可以帮助我解决这个问题？

基本上，对于每个部分，添加小节。

谢谢。

【问题讨论】：

标签： javascript firebase google-cloud-firestore

【解决方案1】：

请试试这个，让我知道是否工作正常。请注意，SubjectBehavior 是从 RxJs 库导入的，我的代码是打字稿代码，因为我认为您使用的是打字稿。

   sb = new SubjectBehavior<[]>();
    var basicArray = [];
           firebase.firestore().collection("sections").get().then((sections) => {
              var myarray = [];
              basicArray = [];
              var count = 0;

              sections.forEach((section) => {
                var sectiondata = section.data();
                sectiondata.__id__ = section.id
                sectiondata.subsections = [];
                myarray.push(sectiondata);
            count++;
            if( count === sections.length()) {
                sb.next(myarray); //or .emit(), i dont remember
            }
                //get subsections

            });

        sb.subscribe( (myArrayElements: any[]) => {
            myArrayElement.foreach( (element) => {
    firebase.firestore().collection("sections").doc(element.__id__).collection("subsections").get().then((subsections) => {
                      subsections.forEach((subsection) => {
                        var subsectiondata = subsection.data();
                        subsectiondata.__id__ = subsection.id;
                        basicArray.push('here element data (sectionData)' + '' + '.subsections', subsectiondata); 
                      });
                    });

                  });
    });
    });

【讨论】：