Javascript 如何在Angular中从http/async调用为接口属性赋值？

我有一个返回JSON对象的服务，我想将此数据分配给接口属性。下面是以下代码，这里的component.ts代码已被剥离，仅包含相关部分

Service.ts文件

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class ApiService {
  constructor(private httpClient: HttpClient) { }

  public getFanSpeed(){
    return this.httpClient.get('http://localhost:4000/auth/get-fan-speed');
  }
}

import { Component, OnInit } from '@angular/core';
import { ApiService } from '../../api.service';

interface CardSettings {
  content: string;
}

@Component({...})
export class DashboardComponent implements OnInit {
  fanSpeed: string;

  ngOnInit() {
    this.apiService.getFanSpeed().subscribe((response)=>{
      this.fanSpeed = response['fanSpeedVar'];
    });
  }

  fanSpeedCard: CardSettings = {
    content: this.fanSpeed
  };

  constructor(private apiService: ApiService) {}
}

import { Component, OnInit } from '@angular/core';
import { ApiService } from '../../api.service';

interface CardSettings {
  content: string;
}

@Component({...})
export class DashboardComponent implements OnInit {
  fanSpeed: string;

  ngOnInit() {
    this.apiService.getFanSpeed().subscribe((response)=>{
      this.fanSpeed = response['fanSpeedVar']
      this.fanSpeedCard.content = this.fanSpeed;
    });
  }

  fanSpeedCard: CardSettings = {
    content: this.fanSpeed
  };

  constructor(private apiService: ApiService) {}
}

Component.ts文件

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class ApiService {
  constructor(private httpClient: HttpClient) { }

  public getFanSpeed(){
    return this.httpClient.get('http://localhost:4000/auth/get-fan-speed');
  }
}

import { Component, OnInit } from '@angular/core';
import { ApiService } from '../../api.service';

interface CardSettings {
  content: string;
}

@Component({...})
export class DashboardComponent implements OnInit {
  fanSpeed: string;

  ngOnInit() {
    this.apiService.getFanSpeed().subscribe((response)=>{
      this.fanSpeed = response['fanSpeedVar'];
    });
  }

  fanSpeedCard: CardSettings = {
    content: this.fanSpeed
  };

  constructor(private apiService: ApiService) {}
}

import { Component, OnInit } from '@angular/core';
import { ApiService } from '../../api.service';

interface CardSettings {
  content: string;
}

@Component({...})
export class DashboardComponent implements OnInit {
  fanSpeed: string;

  ngOnInit() {
    this.apiService.getFanSpeed().subscribe((response)=>{
      this.fanSpeed = response['fanSpeedVar']
      this.fanSpeedCard.content = this.fanSpeed;
    });
  }

  fanSpeedCard: CardSettings = {
    content: this.fanSpeed
  };

  constructor(private apiService: ApiService) {}
}

---

我在ngOnInit（）函数中放了一个console.log，可以看到正确的值，但由于某些原因，它没有正确地分配给接口属性，因此在UI中为空。感谢您的指导。

在您的代码中，fanSpeedCard是一个属性，它是在您的类（仪表板组件）构建时为对象（带有CardSettings接口）指定的值：

fanSpeedCard: CardSettings = {
    content: this.fanSpeed
};

由于最初未定义fanSpeed（仅类型为字符串），并且由于您未在API响应中更新CardSettings对象，所以您的UI不会更改

如评论中所述，您需要确保更新订阅块中CardSettings内容属性的值（不仅仅是fanSpeed）：

---

您没有在ngOnInit（）中正确更新

fanSpeedCard

的

content

porperty值。在ngOnInit（）中，您重新分配了this.fanSpeed值。在这里，您应该将服务响应值分配给

fanSpeedCard

的

content

属性

以下解决方案将解决您的问题

Component.ts文件

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class ApiService {
  constructor(private httpClient: HttpClient) { }

  public getFanSpeed(){
    return this.httpClient.get('http://localhost:4000/auth/get-fan-speed');
  }
}

import { Component, OnInit } from '@angular/core';
import { ApiService } from '../../api.service';

interface CardSettings {
  content: string;
}

@Component({...})
export class DashboardComponent implements OnInit {
  fanSpeed: string;

  ngOnInit() {
    this.apiService.getFanSpeed().subscribe((response)=>{
      this.fanSpeed = response['fanSpeedVar'];
    });
  }

  fanSpeedCard: CardSettings = {
    content: this.fanSpeed
  };

  constructor(private apiService: ApiService) {}
}

import { Component, OnInit } from '@angular/core';
import { ApiService } from '../../api.service';

interface CardSettings {
  content: string;
}

@Component({...})
export class DashboardComponent implements OnInit {
  fanSpeed: string;

  ngOnInit() {
    this.apiService.getFanSpeed().subscribe((response)=>{
      this.fanSpeed = response['fanSpeedVar']
      this.fanSpeedCard.content = this.fanSpeed;
    });
  }

  fanSpeedCard: CardSettings = {
    content: this.fanSpeed
  };

  constructor(private apiService: ApiService) {}
}

---

fanSpeedCard

立即运行。但是API调用需要时间才能得到解决。您可以在订阅区块内分配

fanSpeedCard

值这是否回答了您的问题？谢谢你的解释，谢尔盖！它现在工作得很好。