React Native和Firebase数据库没有映射功能

Question

I have been working for a long time in object parse, this object from Firebase but I can't parse, pls help me how can I do?

{
   "user" : {
       "qweqwe1231" : {
           "-LKmfJ8X9FtL75-03yBf" : {
           "gonderilenkisi":"asdasdad",
           "gonderimzamani":"3123",
           "metin":"dqweqweqe",
           "okundumu":0
       },
       "-LKmgiBm8EB7LFDeOGbH" : {
           "gonderilenkisi":"asdasdad",
           "gonderimzamani":"3123",
           "metin":"dqweqweqe",
           "okundumu":0
       }
   }
}

I get data like this

firebase.database().ref().child('user').child('qweqwe1231').on('value', 
     (data)=>{
         console.log(data.val())

});

And I use to map function but I get an error message "map is not a function"

firebase.database().ref().child('user').child('qweqwe1231').on('value', 
     (data)=>{
         data.val().map((item)=>{ console.log(item.gonderilenkisi)})

});

Answer 1

That error looks correct to me. If you load /user/qweqwe1231 you get this JSON:

{
  "-LKmfJ8X9FtL75-03yBf" : {
    "gonderilenkisi" : "asdasdad",
    "gonderimzamani" : "3123",
    "metin" : "dqweqweqe",
    "okundumu" : 0
  }, 
  "-LKmgiBm8EB7LFDeOGbH" : {
    "gonderilenkisi" : "asdasdad",
    "gonderimzamani" : "3123",
    "metin" : "dqweqweqe",
    "okundumu" : 0
  }
}

This is not an array, so it doesn't have a map() method on it.

You're probably looking to iterate over the sub-objects of the object. Since there is no map() method, you'll have to:

1. extract the keys with Object.keys() .
2. loop over the keys with Array.forEach() or Array.forEach() .
3. look up the subobject for each key and do your thing on that.

So in code:

firebase.database().ref().child('user').child('qweqwe1231').on('value', (snapshot)=>{
    let data = snapshot.val();
    let keys = Object.keys(data);
    keys.forEach((key) => { console.log(data[key]); });
});

Alternatively, you can loop over the children of the DataSnapshot that Firebase passes you with DataSnapshot.forEach() .

So in code:

firebase.database().ref().child('user').child('qweqwe1231')
.on('value',  (snapshot)=>{
    snapshot.forEach((item) => { console.log(item.val().gonderilenkisi); })
});