使用typescript作为自定义数据类型返回Angular中的Promise

Question

I am new in Typescript, and I am trying to return a promise with and object of type Device , but I cannot reach it.

The problem is when I return a Mock everything works good, but when I connect to a real API I have problems here response.json().data as Device .

When I ask for the data in the server and then I try to print this in the template, everything its gone and in the console I have Undefined . Also the console.log that is in device.component.ts in the function getDevices() print like the old status of the object, because when I change the data appear the data that was supposed to show before.

I have a few questions like:

1. How can I access to the response.json().data in the .then of the promise to see what's the structure or what's the data that it has ?

2. How can I map (I think this terminology is correct for Observable , but I don't know how to say it for Promise s) my device object with the data of the API ?

device.component.ts

import { Component, OnInit, Input } from '@angular/core';
import { Device } from './device';
import { DeviceService } from './device.service';

@Component({
selector: 'app-device',
templateUrl: './device.component.html'
})

export class DeviceComponent implements OnInit {
    @Input() private device: Device;
    constructor(private deviceService: DeviceService) {};

    ngOnInit(): void {
        // this.getDevice(40072);
        this.deviceService.getDeviceMock().then(device => this.device = device);
    }

    getDevice(id: number): void {
        this.deviceService.getDevice(id).then(device => this.device = device);
        console.log(this.device);
        // this.deviceService.getDeviceMock().then(device => this.device = device);
    }

    search(id: number): void {
        this.getDevice(id);
}

    save(): void {
        this.deviceService.setDevice(this.device);
    }
}

device.component.html

<input [(ngModel)]="idSearch" type="text" placeholder="Insert ID"  >
<button (click)="search(idSearch)">Search</button>

<div *ngIf="device">
<div>
  <label>Uid: </label>
  <input [(ngModel)]="device.Uid" placeholder="Uid">
</div>

<div>
  <label>VigilId: </label>
<input [(ngModel)]="device.VigilId" placeholder="VigilId">
</div>

<div>
  <label>CmfPhoneNumber: </label>
  <input [(ngModel)]="device.Model.RuntimeSettings.CmfPhoneNumber" placeholder="CmfPhoneNumber">
</div>

<div>
  <label>ReportInterval: </label>
  <input [(ngModel)]="device.Model.RuntimeSettings.ReportInterval" placeholder="ReportInterval">
</div>

<div>
  <label>GeoLocationHighAccuracy: </label>
  <input [(ngModel)]="device.Model.RuntimeSettings.GeoLocationHighAccuracy" placeholder="GeoLocationHighAccuracy">
</div>

<div>
  <label>AlarmCancelTimeout: </label>
  <input [(ngModel)]="device.Model.RuntimeSettings.AlarmCancelTimeout" placeholder="AlarmCancelTimeout">
</div>

<div>
  <label>AdherenceCheckInterval: </label>
  <input [(ngModel)]="device.Model.RuntimeSettings.AdherenceCheckInterval" placeholder="AdherenceCheckInterval">
</div>

<div>
  <label>PreAlarmPeriod: </label>
  <input [(ngModel)]="device.Model.RuntimeSettings.PreAlarmPeriod" placeholder="PreAlarmPeriod">
</div>

<div>
  <label>PingInterval: </label>
  <input [(ngModel)]="device.Model.RuntimeSettings.PingInterval" placeholder="PingInterval">
</div>

<button (click)="save()">Send</button>

device.service.ts

import { Component } from '@angular/core';
import { Device } from './device';
import { Injectable } from '@angular/core';
import { Headers, Http } from '@angular/http';
import 'rxjs/add/operator/toPromise';

import { DeviceMock } from './device-mock'


@Injectable()
export class DeviceService {
    // TODO: Create configuration file.
    private apiUrl = 'https://api.com/api2/v2';
    private headers = new Headers({'Authorization': 'xxxx'});

    constructor(private http: Http) {};
    getDeviceMock(): Promise<Device> {
        return Promise.resolve(DeviceMock)
    }

    getDevice(id: number): Promise<Device> {
        const url = `${this.apiUrl}/device/${id}?names=RuntimeSettings`;
        return this.http.get(url, {headers: this.headers})
            .toPromise()
            .then(response => response.json().data as Device)
            .catch(this.handleError);
    }

    setDevice(device: Device): Promise<Device> {
        this.headers.set('Content-Type', 'application/json');
        const url = `${this.apiUrl}/device/${device.VigilId}?names=RuntimeSettings`;
        return this.http.put(url, JSON.stringify(device), {headers: this.headers})
            .toPromise()
            .then(response => response.json().data as Device)
            .catch(this.handleError);
    }

    private handleError(error: any): Promise<any> {
        console.error('An error occurred', error);
        return Promise.reject(error.message || error);
    }
};

device.ts

export interface Device {
    VigilId: number;
    Uid: string;
    Model: Model;
};

interface Model {
    RuntimeSettings: RuntimeSettings;
};

interface RuntimeSettings {
    ReportInterval: number;
    PingInterval: number;
    PreAlarmPeriod: number;
    AdherenceCheckInterval: number;
    AlarmClearTimeout: number;
    AlarmCancelTimeout: number;
    DailyReportInterval: number;
    GeoLocationRetryCount: number;
    GeoLocationHighAccuracy: true;
    GeoLocationTimeOut: number;
    GeoMaxAgeTimeOut: number;
    CmfPhoneNumber: number;
    PalmTouchTrigger: boolean;
    TouchTriggerCooldownPeriod: number;
    DemoMode: boolean;
    DeviceName: string;
    VerboseLogging: boolean;
};

And this is a response of the API

{
    "VigilId": 41,
    "Uid": "Identi",
    "Model": {
        "RuntimeSettings": {
            "ReportInterval": 900,
            "PingInterval": 300,
            "PreAlarmPeriod": 10,
            "AdherenceCheckInterval": 3600,
            "AlarmClearTimeout": 600,
            "AlarmCancelTimeout": 15,
            "DailyReportInterval": 43200,
            "GeoLocationRetryCount": 3,
            "GeoLocationHighAccuracy": true,
            "GeoLocationTimeOut": 5000,
            "GeoMaxAgeTimeOut": 60,
            "CmfPhoneNumber": "",
            "PalmTouchTrigger": true,
            "TouchTriggerCooldownPeriod": 30,
            "DemoMode": false,
            "DeviceName": "",
            "VerboseLogging": false
        }
    }
}

Answer 1

For question (1):

You must notice that HTTP Client requests are asynchronous. It means the outer/parent function does not hold to wait for the network request to complete, ie, does not block . That is the reason you get "old data" on your getDevices : it prints the object before updating it from server response.

getDevice(id: number): void {
    this.deviceService.getDevice(id)
        .then(device => this.device = device);  // network request is scheduled
    console.log(this.device); // device is printed to log but not necessarily
                              // after the network request returns
}

To solve it, change it to:

getDevice(id: number): void {
    this.deviceService.getDevice(id).then(device => {
        console.log(device); // print to console what is returned from network
        this.device = device;
    });
}

For question (2):

What you are doing this.device = device is correct, that would update your this.device object and point it to the new device object from the server response. (Unless I understood wrongly this question).

Answer 2

For your second question, this line:

response.json().data

appears to be looking for a property of the JSON called "data", but I don't see that anywhere in your example. Does the returned JSON have a property called data?