Javascript 如何将API中的数据加载到Angular 2中的数组中？

所以上周我开始学习AngularJS，结果发现我最好还是学习Angular2。在大量阅读和修改Plunker上的示例应用程序之后，我终于准备好进入Angular 2。上周，我使用AngularJS创建了一个简单的应用程序，可以从API检索数据并将其转换为导航菜单。因此，本周我将尝试将该代码移植到Angular 2

我不能说这很容易，但经过多次修改后，我发现它不起作用的原因是它甚至没有提取数据。下面是我提取数据的服务代码

/src/app/navigation.service.ts

import { NavItem } from './navigation.model';
import { Injectable } from '@angular/core';
import { Http, Headers } from '@angular/http';
import 'rxjs/add/operator/map';

@Injectable()

export class NavService {   
    sections: NavItem[] = [];
    categories: NavItem[] = [];

    constructor(private http: Http) {
    }
    loadSections() {
        //var headers = new Headers();
        //headers.append('Content-Type', 'application/json');
        this.http
            .get('http://localhost:15557/api/navigation/sections/list')
            .map(res => {
                return res.json()
            })
            .subscribe(
            data => {
                this.sections = data;
            },
            err => this.logError(err),
            () => console.log("Loaded all sections")
        );
    }

    loadCategories(id) {
        this.http
            .get('http://localhost:15557/api/navigation/categories/' + id)
            .map(res => res.json())
            .subscribe(
            data => this.categories = [data],
            err => this.logError(err),
            () => console.log("Loaded categories in section with id " + id)
        );
    }

    logError(err) {
        console.error('There was an error: ' + err);
    }
}

export class NavItem {
    // I am never going to use int unless I need to do math operations //
    id: string;
    name: string;
    pid: string;
    slug: string;

    constructor(id: string, name: string, pid: string, slug: string) {
        this.id = id;
        this.name = name;
        this.pid = pid;
        this.slug = slug;
    }
}

import { Component } from '@angular/core';
import { NavItem } from './navigation.model';
import { NavService } from './navigation.service';

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

export class NavComponent {
    public section: NavItem;
    constructor(private service: NavService) { }
    ngOnInit() {
        this.service.loadSections();
    }
}

/src/app/navigation.model.ts

import { NavItem } from './navigation.model';
import { Injectable } from '@angular/core';
import { Http, Headers } from '@angular/http';
import 'rxjs/add/operator/map';

@Injectable()

export class NavService {   
    sections: NavItem[] = [];
    categories: NavItem[] = [];

    constructor(private http: Http) {
    }
    loadSections() {
        //var headers = new Headers();
        //headers.append('Content-Type', 'application/json');
        this.http
            .get('http://localhost:15557/api/navigation/sections/list')
            .map(res => {
                return res.json()
            })
            .subscribe(
            data => {
                this.sections = data;
            },
            err => this.logError(err),
            () => console.log("Loaded all sections")
        );
    }

    loadCategories(id) {
        this.http
            .get('http://localhost:15557/api/navigation/categories/' + id)
            .map(res => res.json())
            .subscribe(
            data => this.categories = [data],
            err => this.logError(err),
            () => console.log("Loaded categories in section with id " + id)
        );
    }

    logError(err) {
        console.error('There was an error: ' + err);
    }
}

export class NavItem {
    // I am never going to use int unless I need to do math operations //
    id: string;
    name: string;
    pid: string;
    slug: string;

    constructor(id: string, name: string, pid: string, slug: string) {
        this.id = id;
        this.name = name;
        this.pid = pid;
        this.slug = slug;
    }
}

import { Component } from '@angular/core';
import { NavItem } from './navigation.model';
import { NavService } from './navigation.service';

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

export class NavComponent {
    public section: NavItem;
    constructor(private service: NavService) { }
    ngOnInit() {
        this.service.loadSections();
    }
}

/src/app/navigation.component.ts

import { NavItem } from './navigation.model';
import { Injectable } from '@angular/core';
import { Http, Headers } from '@angular/http';
import 'rxjs/add/operator/map';

@Injectable()

export class NavService {   
    sections: NavItem[] = [];
    categories: NavItem[] = [];

    constructor(private http: Http) {
    }
    loadSections() {
        //var headers = new Headers();
        //headers.append('Content-Type', 'application/json');
        this.http
            .get('http://localhost:15557/api/navigation/sections/list')
            .map(res => {
                return res.json()
            })
            .subscribe(
            data => {
                this.sections = data;
            },
            err => this.logError(err),
            () => console.log("Loaded all sections")
        );
    }

    loadCategories(id) {
        this.http
            .get('http://localhost:15557/api/navigation/categories/' + id)
            .map(res => res.json())
            .subscribe(
            data => this.categories = [data],
            err => this.logError(err),
            () => console.log("Loaded categories in section with id " + id)
        );
    }

    logError(err) {
        console.error('There was an error: ' + err);
    }
}

export class NavItem {
    // I am never going to use int unless I need to do math operations //
    id: string;
    name: string;
    pid: string;
    slug: string;

    constructor(id: string, name: string, pid: string, slug: string) {
        this.id = id;
        this.name = name;
        this.pid = pid;
        this.slug = slug;
    }
}

import { Component } from '@angular/core';
import { NavItem } from './navigation.model';
import { NavService } from './navigation.service';

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

export class NavComponent {
    public section: NavItem;
    constructor(private service: NavService) { }
    ngOnInit() {
        this.service.loadSections();
    }
}

---

这个代码有什么错

我以前从未使用过这样的服务。也许您的实现有一个简单的错误，但以下是我如何始终在angular中实现服务：

服务 组成部分

---

我以前从未使用过这样的服务。也许您的实现有一个简单的错误，但以下是我如何始终在angular中实现服务：

服务 组成部分

---

乍一看，代码似乎不错。我建议使用Chrome开发工具查看您的网络流量，看看您得到了什么样的响应。另外，我将

console.log

记录订阅中的

数据

响应，以了解实际发生的情况。另外，确保您实际使用的是Angular 2。在Angular 4中，他们改变了您执行HTTP请求的方式。如果您不确定，请按照Targaryen所说的做，并尽可能多地插入

console.log

，以查看流程。我注意到的一件事是，您没有任何机制将

部分

数据从服务返回到您的组件，您看到的是正确的位置吗？乍一看，代码似乎很好。我建议使用Chrome开发工具查看您的网络流量，看看您得到了什么样的响应。另外，我将

console.log

记录订阅中的

数据

响应，以了解实际发生的情况。另外，确保您实际使用的是Angular 2。在Angular 4中，他们改变了您执行HTTP请求的方式。如果您不确定，请按照Targaryen所说的做，并尽可能多地插入

console.log

，以查看流程。我注意到的一件事是，您没有任何机制将

部分

数据从服务返回到您的组件，您找对地方了吗？