Angular2Firebase 通过多个值查询 whereIN

Question

所以我正在寻找与 WHERE IN(val1,val2) 等价的方法，我已经尝试过，但没有用。

Angular 火力地堡

this.firebase.database.list('/favorites', {
            query: {
                orderByChild: 'uID',
                equalTo: [1,2,3,'some value]
            }
});

Answer 1

Firebase 的查询没有 OR 或 IN 运算符。因此，您无法轻松地将上述查询映射到 Firebase。

一种解决方法是对元素实现multiFilter:

public items: FirebaseListObservable<any[]> = null;


ngOnInit() {
    this.items = this.db.list('/favorites', {
        query: {
            orderByChild: 'uID'  
        }
    });

    this.items.subscribe(items => {
       console.info(this.multiFilter(items,{'uID': [1,2,3,'some value]}));
    });
}

public multiFilter(arr: Object[], filters: Object) {
  const filterKeys = Object.keys(filters);
  return arr.filter(eachObj => {
    return filterKeys.every(eachKey => {
      if (!filters[eachKey].length) {
        return true; // passing an empty filter means that filter is ignored.
      }
      return filters[eachKey].includes(eachObj[eachKey]);
    });
  });
};