从angularfire2查询子集 [英] Querying subset from angularfire2
问题描述
pre $ set
$ b $ true $ $ b $ cat $ true $ $ $ $ $ $ $ $ $
snake:true,
bull:true
}
和
set2 = {
dog:true,
cat:true
}
我需要的是在set1中,而不是在set2中,在这种情况下,它会返回:
setresult = {
snake:true,
bull:true
}
我试图用map实现:
<$ p $ (动物)=> {
return animals.map((animal)=> ; {
if(auth.uid == _user。$ key || af.database.object('set2 /'+ animal。$ key)== null){}
else {
return af.database.object('set1 /'+ animal。$ key);
}
})
})
但是,我最终无线第一个用NULL的列表,我只需要结果集。
在此之前感谢。
您可以使用 combineLatest
操作符组成一个observable,它发出一个包含 set1
中的键/值的对象不在 set2
:
导入*作为Rx从rxjs / Rx ;
let set = Rx.Observable.combineLatest(
//使用AngularFire2对象的observables组合set1和set2
的最新值
this.af.database.object('/ set1 /'),
this.af.database.object('/ set2 /'),
//使用运算符的项目函数发出一个
//包含所需值的对象
$ b $(set1,set2)=> {
let result = {};
Object .key(set1).forEach((key)=> {
if(!set2 [key]){
result [key] = set1 [key];
}
});
返回结果;
}
);
set.subscribe((set)=> {console.log(set);});
I need to get a subset from a firebase list. Let's say I have two sets:
set1 = {
dog:true,
cat:true,
snake:true,
bull:true
}
and
set2 = {
dog:true,
cat:true
}
What I need is to get the "in set1, but not in set2", in this case it would return:
setresult = {
snake:true,
bull:true
}
I tried to achieve this with map:
this.setresult = this.af.database.list('/set2/').map((animals) => {
return animals.map((animal) => {
if (auth.uid == _user.$key || af.database.object('set2/' + animal.$key) == null) {}
else {
return af.database.object('set1/' + animal.$key);
}
})
})
But I end up with a list with nulls, and I need only the result set.
Thanks in advance.
You can use the combineLatest
operator to compose an observable that emits an object containing the keys/values from set1
that are not in set2
:
import * as Rx from "rxjs/Rx";
let set = Rx.Observable.combineLatest(
// Combine the latest values from set1 and set2
// using AngularFire2 object observables.
this.af.database.object('/set1/'),
this.af.database.object('/set2/'),
// Use the operator's project function to emit an
// object containing the required values.
(set1, set2) => {
let result = {};
Object.keys(set1).forEach((key) => {
if (!set2[key]) {
result[key] = set1[key];
}
});
return result;
}
);
set.subscribe((set) => { console.log(set); });
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