在可观察范围内使用可观察角度

本文介绍了在可观察范围内使用可观察角度的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在制作角度为6的费用管理器Webapp.我的数据库位于firebase上.我正在使用angularfire2 lib来检索和更新数据.

I am making an expense manager webapp with angular 6. My database is on firebase. I am using the angularfire2 lib to retrieve and update the data.

数据库的设计如下

获取类别的功能是

getCategory(uid:String,categorykey:string):Observable<any> { return this.afdb.object(`users/${uid}/categories/${categorykey}`) .snapshotChanges() .pipe(map(c=>({key:c.payload.key,...c.payload.val()})));}

返回可观察到的费用的函数是

the function that returns observable with an array of expenses is

getExpensesWithKeys(uid:String):Observable<any>{ return this.afdb.list(users/${uid}/expenses) .snapshotChanges() .pipe( map(changes => changes.map(c => ({key:c.payload.key,...c.payload.val()})) ) ); }

在我的组件中，我可以得到我的费用

In my component I can get my expenses as

expenses:Expense[]; getExpensesWithKey("userid-123") .subscribe(expenses=>this.expenses=expenses)

和任何类别

category:Category; getCategory("userid-123",expenses[0].category) .subscribe(category=>this.category=category);

我想创建一个获取支出数组并为每个支出返回类别的可观察对象，我可以将其推入类别数组.我一直在绞尽脑汁，将这两个可观察到的东西与各种rxjs运算符结合在一起，但无济于事.

I want to create an observable that gets the expenses array and returns the category for each expense which i can push into an array of categories. I've been racking my brain to combine the two observables with all kinds of rxjs operaters but to no avail.

非常感谢您的帮助.

只是想添加一些我已经尝试过的方法.我尝试过的一种方法是

edit: Just wanted to add a few methods I tried already. One method I tried was

this.getExpensesWithKeys("user-123") .pipe(mergeMap(expenses=> expenses.map(expense=> this.getCategory("user-123",expense.category)))).subscribe(console.log);

但是它只是发出一个Observables数组.如何获取类别对象并将其推入数组?

but it just emitting an array of Observables. How can i get the category objects and push them into an array?

我尝试过的另一种方法

this.rtdbService.getExpensesWithKeys("user-123") .pipe(map(expenses=> expenses.map(expense=>expense.category))) .pipe(mergeMap(ids=> this.rtdbService.getCategory("user-123",ids))) .subscribe(console.log);

这仅发出类别的键.

我也尝试了以下提供的答案，该答案没有发出任何东西.

I also tried the below provided answer as well which is not emitting anything.

预先感谢

推荐答案

我终于找到了解决方法

getExpensewithCategories(uid:String):Observable<any>{ ; let expwithCat$=this.getExpenses(uid).pipe(mergeMap(expenses =>{ return expenses.map(expense => this.getCategory(uid,expense.category) .pipe(map(cat=> ({expensekey:expense.key, amount:expense.amount, date:expense.date, expcatkey:expense.category, categorykey:cat.key, color:cat.color, name:cat.name}) ) )) } })); return expwithCat$.pipe(mergeAll()) }