无法从firebase中获取嵌套子对象的数据？

Question

我试着用一个特定的ID来获得所有的评论，我尝试了所有的解决方案，但是从来都不起作用。当我尝试获取“post”(第一级节点)时，同样的方法也适用，但嵌套的级别不起作用

数据库：

​

 calculate_post_rating(post_id){

    console.log('this post id: '+post_id);

    let dbref = firebase.database().ref('/user-reviews/'+ post_id + '/');

    dbref.on('child_added', function (data){                

        console.log(data.key); //console is not even printing this, seems like this part is not even executed.

        console.log('rated by user: ' + data.val().rating);

 });

Answer 1

如果以不同的方式构造数据并避免使用key It key，将会更容易：

https://firebase.google.com/docs/database/rest/structure-data#how_data_is_structured_its_a_json_tree

users-reviews: 
 - reviewingUserId 
   - comment: 'Wow'
   - rating: 5
   - subject: 'This may help you out'

Answer 2

代码实际上是工作的，问题是我从循环内部调用了另一个函数"calculate_post_rating(post_id)"，如下所示：

这是他们中的一些人跳过了计算的评级。

let dbref = firebase.database().ref('/posts/');

dbref.on('child_added', function (data){                

    console.log(data.key); //console is not even printing this, seems like this part is not even executed.

    console.log('rated by user: ' + data.val().rating);


let final_rating = calculate_rating(data.key); // this is where the expected final rating wasn't looping properly

});

由此我可以得出结论:由于firebase函数是异步的，您永远不应该从循环中调用外部函数？