[英]DI abstract class instance, angular 5
我有几个组件,应该在注入相同实例的情况下同时获得三个服务。 然后我想“生成”我班的一个新实例,以不时地注入服务。
我的第一个想法是,最好创建一个抽象类并在其中注入所有服务。 然后,我的任何组件都将扩展抽象类,但是这种方法不起作用。
抽象类:
import { Component, Injector } from '@angular/core';
import {GeomqttdataproviderService} from '../protocols/geomqtt/geomqttdataprovider.service';
import {MqttdataproviderService} from '../protocols/mqtt/mqttdataprovider.service';
import {CoapdataproviderService} from '../protocols/coap/coapdataprovider.service';
@Component({
selector: 'app-abstract',
templateUrl: './abstract.component.html',
providers: [
MqttdataproviderService, GeomqttdataproviderService, CoapdataproviderService
],
styleUrls: ['./abstract.component.css']
})
export class AbstractComponent {
protected GeomqttdataproviderService: GeomqttdataproviderService;
protected MqttdataproviderService: MqttdataproviderService;
protected CoapdataproviderService: CoapdataproviderService;
constructor(injector: Injector) {
this.GeomqttdataproviderService = injector.get(GeomqttdataproviderService);
this.MqttdataproviderService = injector.get(MqttdataproviderService);
this.CoapdataproviderService = injector.get(CoapdataproviderService);
}
}
消耗组件之一 :
import { Component, OnInit, Injector } from '@angular/core';
import {AbstractComponent} from '../../abstract/abstract.component';
@Component({
selector: 'app-gauge',
templateUrl: './gauge.component.html',
styleUrls: ['./gauge.component.css'],
providers: [
AbstractComponent
],
})
export class GaugeComponent extends AbstractComponent {
temp = [];
data = [
{
name: '',
value: ''
}
];
constructor(injector: Injector) {
super(injector);
this.CoapdataproviderService.msg$.subscribe(() => {
this.temp = [{name: this.CoapdataproviderService.coapform.addcoaptopicfilter, value: this.CoapdataproviderService.msg}];
this.temp = this.data;
this.data = [{name: this.CoapdataproviderService.coapform.addcoaptopicfilter, value: this.CoapdataproviderService.msg.slice(-1)[0] }];
});
this.GeomqttdataproviderService.geomsg$.subscribe(() => {
this.temp = [{name: this.GeomqttdataproviderService.geomqttform.addgeomqtttopicfilter, value: this.GeomqttdataproviderService.geomsg}]; // nur das letzte wird angezeigt
this.temp = this.data;
this.data = [{name: this.GeomqttdataproviderService.geomqttform.addgeomqtttopicfilter, value: this.GeomqttdataproviderService.geomsg.slice(-1)[0] }];
});
this.MqttdataproviderService.msg$.subscribe(() => {
this.temp = [{name: this.MqttdataproviderService.mqttform.addmqtttopicfilter, value: this.MqttdataproviderService.msg}];
this.temp = this.data;
this.data = [{name: this.MqttdataproviderService.mqttform.addmqtttopicfilter, value: this.MqttdataproviderService.msg.slice(-1)[0] }];
});
}}
我总是收到我的仪表组件中缺少所有服务的错误消息。 但是我不想在app.module中声明它们,因为每次在所有组件中注入抽象类时,我都需要一个新实例。
providers: [AbstractComponent]
没有任何意义,也无法按预期工作。 它将创建一个可以注入的AbstractComponent
类的新实例,这在任何情况下都是不希望的。
到目前为止, 装饰器注释不能被继承 。 providers
属性应从所有子类的AbstractComponent
粘贴到Component
注释。
对于DRYer代码,可以将数组导出并在需要这些提供程序的所有类中重用:
export const DATA_PROVIDERS = [
MqttdataproviderService, GeomqttdataproviderService, CoapdataproviderService
];
...
@Component({
selector: 'app-abstract',
templateUrl: './abstract.component.html',
providers: [DATA_PROVIDERS],
styleUrls: ['./abstract.component.css']
})
...
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