我需要多次订阅才能从Nosql数据库中获取正确的数据.为了获取特定项目的用户列表,我这样做：
ngOnInit() {
//Subscription 1 (Service): Get project data
this.projectService.getCurrentproject().take(1).subscribe(projectData => {
console.log('Got project data.');
//Subscription 2: Get project user IDS
this.af.database.list('/project_roles/'+projectData.$key)
.subscribe((userMeta) => {
});
});
}
>正如您所看到的,订阅中的订阅,订阅中的订阅..并且每个订阅取决于之前的订阅.
>订阅3和4可以是并行的.
解决方法
试试这个.
ngOnInit() {
this.projectService.getCurrentproject().take(1)
.flatMap(projectData => {
return this.af.database.list('/project_roles/'+projectData.$key)
})
.flatMap(userMeta => {
let subs = userMeta.map(projectRole => {
return Observable.zip([
this.af.database.object('/roles/'+projectRole.$value),this.af.database.object('/users/'+projectRole.$key)
]).map(([roleData,user]) => {
user.role = roleData.$value;
return Observable.of(user)
})
});
return Observable.zip(subs)
})
.subscribe(users => {
this.users = users
})
}
