Firebase 在 React Native 數據獲取中返回“未定義”值

Question

我正在嘗試從 firebase 實時數據庫中獲取餐館列表，
我為獲取數據而剪下的代碼 -

_isMounted = false;

state :{
  data: [],
}

constructor(props){
  super(props)

  this.state = {
    data:[],
  }
}

componentDidMount(){
  this._isMounted = true
  this.getData()
}

componentWillUnmount(){
  this._isMounted = false
}

getData(){
  firebase.database().ref('Restaurants/').on("value", snapshot =>{
    let restaurantList = snapshot.val();
    console.log(restaurantList)
    this.setState({data: restaurantList})
  });
}

Firebase 上的數據結構如下 -

數組restaurantList的控制台輸出是 -

Array [
  undefined,
  Object {
    "location": "Testing data",
    "name": "Time Traveller",
    "rating": 4.5,
    "tags": "Indian, Asian",
  },
  Object {
    "locations": "Testing data",
    "name": "Novelty",
    "rating": 4.5,
    "tags": "Indian",
  },
]

我不確定從哪里獲取數組中undefined項目。

Answer 1

請嘗試以下操作：

getData(){
  firebase.database().ref('Restaurants/').on("value", snapshot =>{
  snapshot.forEach((childSub) => {
    let key = childSub.key;
    let restaurantList = childSub.val();
    console.log(restaurantList);
   });
  });
}

undefined 是鍵，嘗試在鍵內迭代並檢索數據