ValueChanges&SnapshotChanges,不再使用FirebaseAngularFire2获取完整列表

最近AngularFire如何处理对象/列表以及引用整个应用程序中的对象,我们遇到了一些严重的问题.

主要的是旧的AngularFireObject & AngularFireList工作与新的相比.我们的应用程序高度依赖于$key价值,因为我们非常规范化(如推荐).

现在,文档使用一个map示例来获取$key值,但是它的工作方式不一样,甚至valueChanges()看起来效果也不一样.

我不完全确定我们现在应该做些什么改变.

考虑:

老路

/* /items/
    a/{name: 'Dennis', city: 'Dallas'}
    b/{name: 'Katie', city: 'Austin'}
    c/{name: 'Will', city: 'Chicago'}
*/
let myAfList = this.af.list('path/to/items');
let itemsFirst, itemsSecond, itemsThird;

myAfList.subscribe(items => itemsFirst = items);

setTimeout(_ => myAfList.subscribe(items => itemsSecOnd= items), 1000);
setTimeout(_ => myAfList.subscribe(items => itemsThird = items), 2000);

/* Results for all three item arrays
    itemsFirst: [
        {name: 'Dennis', city: 'Dallas', $key: 'a'},
        {name: 'Katie', city: 'Austin', $key: 'b'}
        {name: 'Will', city: 'Chicago', $key: 'c'}
    ];
*/

let myAfList = this.af.list('path/to/items').valueChanges();
let itemsFirst, itemsSecond, itemsThird;

myAfList.subscribe(items => itemsFirst = items);

setTimeout(_ => myAfList.subscribe(items => itemsSecOnd= items), 1000);
setTimeout(_ => myAfList.subscribe(items => itemsThird = items), 2000);

/* Results for ONLY itemsFirst
    itemsFirst: [
        {name: 'Dennis', city: 'Dallas'},
        {name: 'Katie', city: 'Austin'}
        {name: 'Will', city: 'Chicago'}
    ];
*/

let myAfList = this.af.list('path/to/items').snapshotChanges()
            .map(actiOns=> {
                return actions.map(action => {
                    const $key = action.payload.key;
                    const data = { $key, ...action.payload.val() };
                    return data;
                });
            });
let itemsFirst, itemsSecond, itemsThird;

myAfList.subscribe(items => itemsFirst = items);

setTimeout(_ => myAfList.subscribe(items => itemsSecOnd= items), 1000);
setTimeout(_ => myAfList.subscribe(items => itemsThird = items), 2000);

/* Results for ONLY itemsFirst
    itemsFirst: [
        {name: 'Dennis', city: 'Dallas', $key: a},
        {name: 'Katie', city: 'Austin', $key: b}
        {name: 'Will', city: 'Chicago', $key: c}
    ];
*/

let myAfList = this.af.list('path/to/items');
myAfList.valueChanges().subscribe(items => itemsFirst = items);