如何基于角度4

Question

基于UI（prod，dev，qa）的用户输入，我想选择不同的后端环境并触发各自的后端API。我有一个家庭组件。从那里，我正在使用下拉列表捕获用户环境。然后将数据传递给服务，但是我无法动态更改env变量值。

家庭组件HTML

<select #tbchange (change)="OntbChange($event.target.value)">
  <option value="choose">Select</option>
  <option value="a">a</option>
  <option value="b">b</option>
  <option value="c">c</option>
</select>

home.component.ts

import { element } from 'protractor';
import { SailsService } from './../services/sails.service';
import {Component, ViewChild, ElementRef, Output, EventEmitter} from '@angular/core';
import {FormBuilder, FormControl, FormGroup, FormsModule, ReactiveFormsModule, Validator, Validators} from '@angular/forms';

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

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.css']
})

@ViewChild('tbchange') tbchange: ElementRef;

export class HomeComponent  {
  onSubmit() {
    console.log(this.conn.nativeElement.value);
    if (this.conn.nativeElement.value === 'l2') {
      if (this.myForm.value.uuid.length !== 0) {
        this.uuid = this.myForm.value.uuid;
        // this.testBed = this.myForm.get('testbed').value;
        console.log(this.uuid);
        // console.log(this.testBed);
        this
          .sails
          .getData(this.myForm.value.uuid, this.tbchange.nativeElement.value)
          .then((success) => {
            const user = success.json();
            this.l2UserData = user.userData;
            if (this.l2UserData.length > 0) {
              this.noResponse = false;
              this.isL2Connection = true;
              this.isL3Connection = false;
          } else {
            this.noResponse = true;
          }
          })
          .catch((error) => {
            this.isL2Connection = true;
            this.isL3Connection = false;
            console.log('Error is', error);
          })
      }
    }
}

sails.service.ts

import {Injectable} from '@angular/core';
import {Http} from '@angular/http';
import {LogService} from './log.service';
import {environment} from '../../environments/environment';
import {ApiService} from './http/api.service';
import 'rxjs/add/operator/map';

export const SERVICE_AUDIENCE = 'a';

@Injectable()
export class SailsService extends ApiService {
  constructor(http: Http,
    log: LogService) {
    if (!environment.services || !environment.services[SERVICE_AUDIENCE]) {
      `enter code here`throw new Error('environment.service for the `enter code here`LabApiService is `enter `enter code here`enter code here`code here`missing');
        }
        super(SERVICE_AUDIENCE, http, log);
      }

  getData(uuid, env) {
    return this
      .get(`/api/connection/xxx?uuid=${uuid}&env=${env}`)
      .toPromise()
  }

env.ts

export const environment = {
  production: false,
  debug: {
    apiCalls: '*'
  },
  services: {
    'a': 'http://xxxx:8000',
    'b': 'http://localhost:1337',
    'c': 'xxxxxxx:9000'
  }
};

我有一个API服务，其中编写了较低级的URL连接和REST方法。我面临的问题是，在用户API触发器上调用getData函数之前，构造函数已经初始化并存储export const SERVICE_AUDIENCE = 'a';的值。我必须以某种方式基于用户选择环境来动态更改SERVICE_AUDIENCE的值，并触发不同的环境字符串。我该如何实现？