Angular filter Observable array

问题

I have an Observable array and I want to filter/find the Project by name. When I try to use the filter option it is saying

ProjectService.ts

import { Injectable } from '@angular/core';
import { Project } from "../classes/project";
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';

import { Http } from '@angular/http';


@Injectable()
export class ProjectService {

  private projects: Observable<Project[]>;

  constructor(private http: Http) {
    this.loadFromServer();
  }

  getProjects(): Observable<Project[]> {
    return this.projects;
  }

  private loadFromServer() {
    this.projects = this.http.get('/api/projects').map(res => res.json());
  }

  getProjectByName(name: String) {
    return this.projects.filter(proj => proj.name === name);
  }


}

Project Class

export class Project {
    public name: String;
    public miniDesc: String;
    public description: String;
    public category: String[];
    public images: any[];
}

回答1:

it should be:

getProjectByName(name: String) {
  return this.projects
    .map(projects => projects.filter(proj => proj.name === name));
}

you misunderstood about filter operator. The operator using to filter data return from stream. Your stream return array of object, so you need filter array to get you needed value.

The solution above will return an array after filtered, if you wanna get only one value, using following solution

getProjectByName(name: String) {
  return this.projects
    .map(projects => {
      let fl = projects.filter(proj => proj.name === name);
      return (fl.length > 0) ? fl[0] : null;
    });
}

回答2:

In angular 7 you dont need map to filter the value on a subscribed value

getProjectByName(name: String) {
  return this.projects
    filter(proj => proj.name === name));
}

回答3:

In your Service you can define <any> type or Project[] type to return the response value and same could be continue with filter. e.g. <any>res.json() or <Project[]>res.json()

and also update your class as suggested by @Sajeetharan

ProjectService.ts

import { Injectable } from '@angular/core';
import { Project } from "../classes/project";
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';

import { Http } from '@angular/http';


@Injectable()
export class ProjectService {

  private projects: Observable<Project[]>;

  constructor(private http: Http) {
    this.loadFromServer();
  }

  getProjects(): Observable<Project[]> {
    return this.projects;
  }

  private  loadFromServer(): Observable<any> {
    this.projects = this.http.get('/api/projects').map((res: Response)=> <any>res.json());
  }

  getProjectByName(name: string) {
    return this.projects.filter(proj => proj.name === name);
  }   
}

*always write your filters, conditions or manipulation in component not in services.

来源：https://stackoverflow.com/questions/43430715/angular-filter-observable-array

标签

angular

typescript

rxjs