angularjs – Angular2:使用自定义装饰器或注释将提供程序注入到组件中?

我正在使用一个简单的TabsProvider隐藏Ionic 2中的某些@Pages(一个Ionic 2装饰器)的标签:

tabs.ts

import { Injectable } from 'angular2/core';
import { BehaviorSubject } from 'rxjs';

@Injectable()
export class TabsProvider {
  currentState = new BehaviorSubject<boolean>(true);
  public showTabs(){
    this.currentState.next(true);
  }
  public hideTabs(){
    this.currentState.next(false);
  }
}

tabs组件订阅currentState,TabsProvider注入各种页面,如下所示:

样品page.ts:

import {Page} from 'ionic-angular';
import { TabsProvider } from './tabs';

@Page({
  ...
})
export class SamplePage {
  tabsProvider: TabsProvider;

  constructor(tabsProvider: TabsProvider) {
    this.tabsProvider = tabsProvider;
  }

  onPageWillEnter(){
    this.tabsProvider.hideTabs();
  }

  onPageWillLeave(){
    this.tabsProvider.showTabs();
  }
}

这段代码几乎都是样板文件,如果我可以在装饰器(或注释)中定义这个功能,那将会更加清晰,例如:

import { Page } from 'ionic-angular';
import { hideTabs } from './tabs';

@hideTabs()
@Page({
  ...
})
export class BuyPage {
}

但我无法确定如何注入TabsProvider并将onPageWillEnter和onPageWillLeave方法添加到SamplePage.

装饰器(或注释)可以以某种方式注入额外的Angular提供者吗?

到目前为止我得到的最远:

在tabs.ts中:

export function hideTabs() {
  return function(cls: any) {
    cls.prototype.onPageWillEnter = function() {
      this.tabsProvider.hideTabs();
    };
    cls.prototype.onPageWillLeave = function() {
      this.tabsProvider.showTabs();
    };
    return cls;
  }
}

这使我们成为我们正在寻找的部分,但仍然需要导入TabsProvider并将其作为特定实例成员注入:

样品page.ts

import {Page, Events} from 'ionic-angular';
import { hideTabs, TabsProvider } from './tabs';

@hideTabs()
@Page({
  ...
})
export class SamplePage {
  constructor(public tabsProvider: TabsProvider) {
  }
}

是否可以将其完全抽象为@hideTabs()?

编辑:

选项卡组件的相关部分(对于任何对实现感兴趣的人)pages / tabs / tabs.ts:

import { Page } from 'ionic-angular';
import { TabsProvider } from './tabs';

@Page({
  ...
})
export class TabsPage {

  ...

  currentState: boolean;
  constructor(TabsProvider: TabsProvider) {
    TabsProvider.currentState.subscribe((state: boolean) => {
      this.currentState = state;
    });
  }
}

页/标签/ tabs.html:

<div [ngClass]="{'hide-tabs': !currentState}">
  <ion-tabs>
    ...
  </ion-tabs>
</div>

页/标签/ tabs.scss:

.hide-tabs ion-tabbar-section {
    display: none;
}

最佳答案 我刚遇到同样的问题,这就是我提出的解决方案.一般方法是:

>使用Reflect.getOwnMetadata从类中读取现有依赖项.
>添加到依赖项列表
>创建一个新的构造函数,它包装旧的构造函数并处理这些依赖项.

tabs.ts:

    import TabsProvider from "./tabs";

    export function hideTabs() {
      return function(cls: Function) : any {

        // Save existing onPageWillEnter and onPageWillLeave inplementations
        let enter = cls.prototype.onPageWillEnter || function () {};
        let leave = cls.prototype.onPageWillLeave || function () {};

        // Create new constructor for class
        const newCls = function (tabsProvider, ...args) {
            this.__hideTabs__tabsProvider = tabsProvider;
            return cls.apply(this, args);
        }

        // Copy prototype to new constructor
        newCls.prototype = constructor.prototype;

        // Copy metadata to new constructor
        let metadatakeys = Reflect.getMetadataKeys(cls);
        metadatakeys.forEach(function (key) {
          Reflect.defineMetadata(key, Reflect.getOwnMetadata(key, cls), newCls)
        });

        // Read dependencies list from 'cls', add our own dependency, and write list to 'newCls'
        let dependencies = Reflect.getOwnMetadata('design:paramtypes', cls);
        dependencies = [TabsProvider].concat(dependencies)
        Reflect.defineMetadata('design:paramtypes', params, newCls);

        // Define new onPageWillEnter and onPageWillLeave implementation which implement tab show/hide functionality
        // and also call the old implementation saved above (if they exist)
        newCls.prototype.onPageWillEnter = function() {
          this.tabsProvider.hideTabs();
          enter.apply(this, arguments);
        };

        newCls.prototype.onPageWillLeave = function() {
          this.tabsProvider.showTabs();
          leave.apply(this, arguments);
        };

        return newCls;
      }
    }

我还建议在@Page装饰器下面移动@hideTabs装饰器

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