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I am doing the front end of a project using Angular 6, but I am beginner in both Angular and Typescript and I am trying to use the interfaces of Typescript as in Java, injecting them to use the methods and tals, the problem is the following:
*I have an interface with the signature of the methods;
*I have a class q implements this interface and has the methods;
*I have a component q calls the interface on Contructor thus private myInterface: MyInterface and, at least in Java what I would do is make this attribute receive a new object from the class q implements this interface (this.myInterface = new ObjetoQueImplementa();) and could use their methods normally, but in Typescript is different, and I even saw articles and some examples that I found there with a certain injection of dependency as in Java but none of them came to help me, I will leave my code here I hope someone can help me here.
Interface:
import {Agenda} from "../model/agenda";
import {Observable} from "rxjs/index";
export interface AgendaCommandRepository {
insert(agenda: Agenda): Observable<Agenda>;
update(agenda: Agenda): Observable<Agenda>;
deleteAgenda(id: number): Observable<number>;
}
Class implementing the interface:
import { Injectable } from '@angular/core';
import { AgendaService } from '../service/agenda-command.service';
import { AgendaCommandValidator } from '../validator/agenda-command-
validator';
import { Agenda } from '../../model/agenda';
import { Observable } from 'rxjs/index';
@Injectable({
providedIn: 'root'
})
export class AgendaCommandRepositoryImpl implements AgendaCommandRepository {
constructor(private service: AgendaService, private validator:
AgendaCommandValidator) { }
insert(agenda: Agenda): Observable<Agenda> {
if (this.validator.validaInsert(agenda)) {
return this.service.insert(agenda);
}
return null;
}
update(agenda: Agenda): Observable<Agenda> {
if (this.validator.validaUpdate(agenda)) {
return this.service.update(agenda);
}
return null;
}
deleteAgenda(id: number): Observable<number> {
if (this.validator.validaDelete(id)) {
return this.service.deleteAgenda(id);
}
return null;
}
}
Component that injects the interface to call its methods and execute the code of the class q implements the interface:
import {Component, Inject, OnInit} from '@angular/core';
import { AgendaCommandRepositoryImpl } from "../../repository/agenda-
command-repository-impl";
import { Agenda } from "../../../model/agenda";
import { AgendaQueryRepository } from "../../../query/repository/agenda-
query-repository";
import { ActivatedRoute } from '@angular/router';
import { AgendaCommandRepository } from "../../agenda-command-repository";
@Component({
selector: 'app-agenda',
templateUrl: './agenda-command.component.html',
styleUrls: ['./agenda-command.component.css']
})
export class AgendaCommandComponent implements OnInit {
agenda: Agenda;
id: number;
titulo: string; // para teste
constructor(private repository: AgendaCommandRepository, private
queryRepository: AgendaQueryRepository, private route: ActivatedRoute) {}
ngOnInit() {
this.id = +this.route.snapshot.paramMap.get('id');
if (this.id) {
this.queryRepository.findById(this.id).subscribe(agenda => this.agenda
= agenda);
this.titulo = "Edição";
} else {
this.agenda = new Agenda();
this.titulo = "Cadastro";
}
}
salvar() {
if (this.id) {
this.repository.update(this.agenda).subscribe();
} else {
this.repository.insert(this.agenda).subscribe();
}
}
}
Your class
AgendaCommandRepositoryImplis not implementingAgendaCommandRepository, only has methods with the same name, missing theimplements. When defining in the constructor which type isAgendaCommandRepositoryit will try to use the interface as value which will not work, you must directly pass the implementationAgendaCommandRepositoryImpl– Costamilam
@Guilhermecostamilam I’m sorry I copied wrong, the idea was to have the
implementsla, nn preucupe that I have already edited and fixed my mistake, but you have some idea how to solve this my problem?– Bruno
Or you pass
AgendaCommandRepositoryImplin the constructor orprivateand in an instance the classthis.repository = new AgendaCommandRepositoryImpl();– Costamilam
@Guilhermecostamilam pseh I tried this second option and it did not work, it gives an error saying that the
this.repositoryexpects 2 arguments and this getting 0, in my conception was to work but as nn understand mto of typescript my conception nn worth nothing, has some other idea?– Bruno
Yes, this error occurs because the class
AgendaCommandRepositoryImplneed to receive two parameters in your constructor, you need to take them when instantiating, when you create a direct instance in the constructor arguments the TS makes it automatic for you– Costamilam
@Guilhermecostamilam I think I understand what you mean, but does nn have an easier/more practical way of doing this? is that it seems to me that way "gambiarrento", it gets a code very ugly, like, the code would look like this
this.repository = new AgendaCommandRepositoryImpl(new AgendaService(new HttpClient()), new AgendaCommandValidator());There’s got to be some way to do it Without getting all twisted up...– Bruno
Yes pass in constructor parameter the class that implements
– Costamilam
@Guilhermecostamilam type like this
constructor(private repository: AgendaCommandRepository, private repositoryImpl: AgendaCommandRepositoryImpl) { };?– Bruno
pq if that’s the way it is, nn I want to have it instantiated or I would use its object msmo and nn would need the interface, I found a way to do exactly what I want and it works but I took from an example of Angular 4 I think and tbm this way that I found is more laborious and nn know if it’s worth it, look here dps to see this article sera q vc nn knows a way to make the result of this article without that gambiarra and all work?
– Bruno