angularfire2

问题 Im trying to get some Ids from a collection, and then trying to use each of these Ids to get more data from another collection. Here is what I got done so far: Basically, I have blog app in which multiple users will be able to post an article. And said article has categories. The thing is, when a user selects a category to filter, it will bring me all USERS that have an article in said category (instead of bringing all articles of the selected category). So, in Firestore I have: categories/

问题 I want to create a user registration with custom usernames. I store the user's username on a user document in Firestore. How can I validate a username already exists in my Users Collection? Maybe someone already have snippet for reactive form validation? 回答1: There is no efficient way to check all documents in a collection for a specific value. You would have to read each document in turn, and check them. That is prohibitive both from a performance and a cost standpoint. What you can instead

问题 I want to perform some firebase operation inside a loop in angular. When I send an HTTP request to firebase it returns an array of observables so using forkjoin i convert this array of observables into single observables. Now the problem is when I subscribe to these new observables I didn't get anything get_student_email() { this.get_project_service .get_project_by_doc_id(this.batchID, this.projectID) .subscribe((res) => { this.response = res; this.email = this.response.student; let data =

问题 I want to perform some firebase operation inside a loop in angular. When I send an HTTP request to firebase it returns an array of observables so using forkjoin i convert this array of observables into single observables. Now the problem is when I subscribe to these new observables I didn't get anything get_student_email() { this.get_project_service .get_project_by_doc_id(this.batchID, this.projectID) .subscribe((res) => { this.response = res; this.email = this.response.student; let data =

来源： https://stackoverflow.com/questions/52572597/angular-firestore-how-to-get-array-not-contain

来源： https://stackoverflow.com/questions/52572597/angular-firestore-how-to-get-array-not-contain

来源： https://stackoverflow.com/questions/41021487/angular-2-subscribe-from-component-or-service

来源： https://stackoverflow.com/questions/41021487/angular-2-subscribe-from-component-or-service

来源： https://stackoverflow.com/questions/52454480/missing-or-insufficient-permissions-firestore

来源： https://stackoverflow.com/questions/49729125/how-to-retrieve-id-of-just-inserted-firestore-document-with-angularfire2