Question

我有以下问题：我从JSON API中提取数据。我目前为每个数据模型（例如文章，用户等）提供服务，并为每个数据模型提供模型类。但这是疯狂的，不能真正维持。所以我想重构一下，这样我就可以为每个数据模型和一个统一的DataAPIService建立一个接口和一个模型类。

问题是，DataAPIService中查询API的函数不应返回JSON，而是返回已查询类型的对象或对象集合。所以我需要一种方法将接口或类型传递给服务的查询方法，然后初始化这种类型的新对象。

这可能吗？我有道理吗？这里有一些代码可以帮助理解我的意思并展示我目前的进展。

import { Injectable } from '@angular/core';

import { AuthHttp } from 'angular2-jwt';
import 'rxjs/add/operator/map';

import { Config } from '../config/env.config';

@Injectable()
export class DataAPIService {

  constructor(
    private authHttp: AuthHttp
  ) {}

  // This function will be called to retrieve data (for example from a Component). 
  // I want to pass in the object type or interface so that I only have one 
  // getIndex() function and not one for every data type.

  getIndex(page:number = 1, object_name:string, object_type) {
    return this.authHttp.get(Config.API_ENDPOINT + '/' + object_name + '?page=' + page)
      .map(res => res.json())
      .map(res => {
        return this.fromJson(res.data, object_type);
      });
  }

  // This function just checks which attributes are present in the object type 
  // and fills a new object of this type with the values from JSON.  
  // This is partly pseudo-code since I don't know how to solve this.

  fromJson(input_json: any, object_type) {
    // The next line is obviously not working. This is what I'm trying to figure out
    var object:object_type = new object_type();
    var json_attributes = input_json.attributes;
    for (var key in json_attributes) {
      if (object.hasOwnProperty(key)) {
        object[key] = json_attributes[key];
      }
    }
    object.id = input_json.id;
    return object;
  }

}

Answer 1

你可以做的是使用泛型（如果你不知道它们是什么，我建议使用谷歌搜索）。

@Injectable()
export class DataAPIService {

  constructor(
    private authHttp: AuthHttp
  ) {}

  // This function will be called to retrieve data (for example from a     Component). 
  // I want to pass in the object type or interface so that I only have one 
  // getIndex() function and not one for every data type.

  getIndex<T>(page:number = 1, object_name:string): Observable<T> {
    return this.authHttp.get(Config.API_ENDPOINT + '/' + object_name +     '?page=' + page)
      .map(res => res.json());
  }

只需将T泛型添加到您的方法中，就可以将返回类型定义为类型为T的值的Observable.res.json（）将只创建一个对象，如果它返回给此调用者方法，他只会看到类型为T的值的可观察值。无需为接口编写这样的特定解析函数。

Answer 2

这就是我解决整个问题的方法。对我来说重要的是，生成的对象不是通用对象，而是Post类型的对象。我也想使用接口，我希望对象的初始化很容易。

首先，我有一个基类，所有数据模型都从该基类继承。

<强>基model.model.ts

import * as _ from 'lodash';

export class BaseModel {

  public id: string;
  [key: string]: any;

  constructor(private data?: any) {
    // This basically does the initialization from a variable json object. 
    // I later on just pass the json data into the constructor.
    if (data) {
      this.id = data.id;
      _.extend(this, data.attributes);
    }
  }
}

现在继承自Base Model的实际模型：

member.model.ts

// The actual model. It has an interface and extends the base class 
// (so that the main logic is just in one place - DRY)

import { BaseModel } from './base-model.model';

interface MemberInterface {
  email:string;
  name:string;
}

export class Member extends BaseModel implements MemberInterface {

  email:string;
  name:string;

  constructor(data?: any) {
    super(data);
  }

}

让我们用它。使用从API中提取数据的服务

import { Injectable } from '@angular/core';
import { AuthHttp } from 'angular2-jwt';
import 'rxjs/add/operator/map';
import { Config } from '../config/env.config';

@Injectable()
export class MemberService {

  constructor(public authHttp: AuthHttp) {}

  // Calls the API and returns the result.
  // authHttp works very similar to http. Just with added JWT protection
  // check it out on GitHub: angular2-jwt
  getIndex(page:number = 1):any {
    let url = [Config.API_ENDPOINT, 'members', '?page='].join('/');
    return this.authHttp.get(url + page)
      .map(res => res.json())
      .map(res => {
        return res;
      });
  }

  // Simpler example when just getting one entry
  getOne(id: string):any {
    let url = [Config.API_ENDPOINT, 'members', id].join('/');
    return this.authHttp.get(url)
      .map(res => res.json())
      .map(res => {
        return res;
      });
  }


}

最后让我们一起使用Model类和服务

import { Component, OnInit } from '@angular/core';

import { MemberService } from '../shared/index';
import { Member } from '../shared/models/member.model';

@Component({
  moduleId: module.id,
  selector: 'app-member-list',
  templateUrl: 'member-list.component.html',
  styleUrls: ['member-list.component.css']
})
export class MemberListComponent implements OnInit {

  private members: Array<Member>;
  private member: Member;

  constructor(private memberService: MemberService) {
    this.members = [];
    this.member = new Member();
  }

  ngOnInit():any {
    // Pull the list on initialization
    this.getIndex(1);
  }

  // For the index
  getIndex(page:number = 1):Array<Member> {
    this.memberService.getIndex(page).subscribe(
      res => {
        this.members = [];
        for(let i = 0; i < res.data.length; i++) {
          let member = new Member(res.data[i]);
          this.members.push(member);
        }
      },
      err => console.log(err)
    );
  }

  // Simpler version with just one entry 
  getOne():any {
    this.memberService.getIndex(page).subscribe(
      res => {
        this.member = new Member(res.data.attributes);
      },
      err => console.log(err)
    );
  }

}

Angular 2 Typescript：是否可以将接口作为参数传递给函数？

2 个答案: