Angular2 Http 请求

Question

Angular2 Http 请求

javascriptangulartypescriptangular2-http

9

你好，我正在尝试使用Angular2中的HTTP模块进行get请求。

在Typescript（1.5）中编译一切顺利，但是Chrome在控制台中显示以下错误：

EXCEPTION: Error during instantiation of EntryList!. ORIGINAL
EXCEPTION: TypeError: Cannot read property 'merge' of undefined
ORIGINAL STACKTRACE: TypeError: Cannot read property 'merge' of undefined
at mergeOptions (angular2.dev.js:27991)  
at execute.Http.get (angular2.dev.js:28052)  
at EntryService.getEntries (services.js:17)
at new EntryList (entry-list.js:20)

Services.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
import { Http, Observable } from "angular2/angular2"

export class EntryService {
    private _entries: Array<string>;
    private _http : Http;

    constructor() {     
        this._entries = ["test1", "test2", "test3"];
        this._http = new Http;      
    }

    get Entries() : Array<string> {
        return this._entries;
    }

    getEntries()
    {
        console.log(this._http);
        return this._http.get('http://localhost:53338/api/decisions')       
            .toRx()
            .map((response) => { 
                response.json()
            });     
    }
}

entry-list.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
/// <reference path="../modules/services.ts" />

import { Component, View, NgFor } from "angular2/angular2"
import { EntryService } from "modules/services"

@Component({
    selector: 'entry-list'  
})
@View({
    directives: [ NgFor ],
    templateUrl: "../views/entry-list.html" 
})
export class EntryList {
    entries: Array<string>; 

    constructor(public service: EntryService) {     
        this.entries = this.service.Entries;
        this.service.getEntries().subscribe((response) => {     
            console.log(response);
        }); 
    }
}

app.ts

/// <reference path="typings/angular2/angular2.d.ts" />
/// <reference path="components/entry-list.ts" />
/// <reference path="modules/services.ts" />

import { Component, View, bootstrap, NgFor } from "angular2/angular2"
import { EntryList } from "components/entry-list"
import { EntryService } from "modules/services"

@Component({
    selector : "app",
    bindings: [ EntryService ]  
})
@View({
    directives: [ EntryList ],
    templateUrl: "views/app.html"   
})
class App { 
    constructor() {
        console.log('hit');
    }
}

bootstrap(App);

index.html

<html>
    <head>
        <title>SCM</title>
        <script src="https://github.jspm.io/jmcriffey/bower-traceur-runtime@0.0.88/traceur-runtime.js"></script>
        <script src="https://jspm.io/system@0.16.js"></script>      
        <script src="https://code.angularjs.org/2.0.0-alpha.34/angular2.dev.js"></script>
    </head>
    <body>
        <app></app>
        <script>System.import('app')</script>
    </body>
</html>

我查看了 angular.io 网站上的 API 文档，但无法找到问题所在。

更新

Services.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
import { Http, Observable, httpInjectables } from "angular2/angular2"

export class EntryService {
    private _entries: Array<string>;    

    constructor(private http: Http) {       
        this._entries = ["test1", "test2", "test3"];            
    }

    get Entries() : Array<string> {
        return this._entries;
    }

    getEntries()
    {
        console.log(this.http);
        return this.http.get('http://localhost:53338/api/decisions')        
            .toRx()
            .map((response) => { 
                response.json()
            });     
    }
}

entry-list.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
/// <reference path="../modules/services.ts" />

import { Component, View, NgFor, Http, httpInjectables } from "angular2/angular2"
import { EntryService } from "modules/services"

@Component({
    selector: 'entry-list',
    bindings : [ Http, httpInjectables ]
})
@View({
    directives: [ NgFor ],
    templateUrl: "../views/entry-list.html" 
})
export class EntryList {
    entries: Array<string>; 

    constructor(public service: EntryService) {     
        this.entries = this.service.Entries;
        this.service.getEntries().subscribe((response) => {     
            console.log(response);
        }); 
    }
}

app.ts

/// <reference path="typings/angular2/angular2.d.ts" />
/// <reference path="components/entry-list.ts" />
/// <reference path="modules/services.ts" />

import { Component, View, bootstrap, NgFor, Http, httpInjectables } from "angular2/angular2"
import { EntryList } from "components/entry-list"
import { EntryService } from "modules/services"

@Component({
    selector : "app",
    bindings: [ EntryService, Http, httpInjectables ]   
})
@View({
    directives: [ EntryList ],
    templateUrl: "views/app.html"   
})
class App { 
    constructor() {
        console.log('hit');
    }
}

bootstrap(App);

不需要对index.html进行任何更改。

编辑：我的services.ts文件已更改以使其正常工作：

/// <reference path="../typings/angular2/angular2.d.ts" />
import { Injector, Http, httpInjectables } from "angular2/angular2"

export class EntryService {
    private _entries: Array<string>;    
    private http: Http;

    constructor() {     
        this._entries = ["test1", "test2", "test3"];        

        var injector = Injector.resolveAndCreate([
                httpInjectables,
                Http
            ]);
        this.http = injector.get(Http);                 
    }

    get Entries() : Array<string> {
        return this._entries;
    }

    getEntries()
    {       
        return this.http.get('http://localhost:53338/api/decisions')        
            .toRx()
            .map(response => response.json());      
    }
}

- Werner Swart

2个回答

2

你真的想为了CRUD / HTTP请求而使用另一个库吗？

我强烈建议使用 ES6 中默认的 fetch。我认为它不仅比 angular2/http 更简单，而且在当前和未来版本中也是标准。

** 它可以直接在 Safari、Chrome、IE-Edge 和 Firefox 上运行。

- user2379441

3

需要翻译的内容：An example would be helpful to support your case。一个例子会有助于支持你的论点。 - Serj Sagan

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Arnaud Boeglin · Accepted Answer

不要自己实例化 Http，而是获取注入的实例：

public constructor(http : Http) {
    this.http = http;
}

文档中写道：

Http可以作为一个可注入的类使用，具有执行http请求的方法。

因此，我不确定如果您自己实例化它会得到什么结果，但由于一些未定义的内部问题，它无法执行get请求。

编辑：添加更多来源。

@Injectable()
export class Http {
    constructor(protected _backend: ConnectionBackend, protected _defaultOptions: RequestOptions) {}

    /**
     * Performs a request with `get` http method.
     */
    get(url: string, options?: RequestOptionsArgs): EventEmitter {
        return httpRequest(this._backend, new Request(mergeOptions(this._defaultOptions, options, RequestMethods.GET, url)));
  }
}

我在这里添加了Github存储库中Http类的一小部分。你可以看到构造函数中给出了_backend和_defaultOptions，而你没有提供。方法get()将根据选项参数和构造函数中给出的_defaultOptions构建请求选项，因为你没有提供这些选项中的任何一个，我认为它会在mergeOptions调用中崩溃，你可以在这里找到：

function mergeOptions(defaultOpts, providedOpts, method, url): RequestOptions {
  var newOptions = defaultOpts;
  if (isPresent(providedOpts)) {
    // Hack so Dart can used named parameters
    newOptions = newOptions.merge(new RequestOptions({
      method: providedOpts.method,
      url: providedOpts.url,
      search: providedOpts.search,
      headers: providedOpts.headers,
      body: providedOpts.body,
      mode: providedOpts.mode,
      credentials: providedOpts.credentials,
      cache: providedOpts.cache
    }));
  }
  if (isPresent(method)) {
    return newOptions.merge(new RequestOptions({method: method, url: url}));
  } else {
    return newOptions.merge(new RequestOptions({url: url}));
  }
}

在函数的最后一个 if/else 块中。更多信息请查看源文件，位于这里。