动手写一个angular版本的Message组件

学习一个框架或库的最好方法是看官方文档，并着手去写例子。最近在利用空闲的时间学习angular，那今天就尝试写一个message组件，并通过message服务动态加载message组件。
我所参与的项目基本是用jquery完成的。之前，在项目中自己动手写过一个简单的message插件，样子如下图。

success.jpg

那现在就使用angular（版本5.0.0）来实现message组件。

message组件

message组件要根据传入的类型、消息和duration来显示。创建三个文件：message.component.ts,message.component.html,message.component.css，代码如下。

//message.component.ts
import {Component,Input,OnInit,ChangeDetectionStrategy} from '@angular/core';
import {
   trigger,
   state,
   style,
   transition,
   animate
 } from '@angular/animations';
const mapping={
   success:'glyphicon-ok-sign',
   warning:'glyphicon-exclamation-sign',
   error:'glyphicon-exclamation-sign',
   info:'glyphicon-ok-circle'
}
@Component({
   selector:'upc-ng-message',
   templateUrl:'./message.component.html',
   styleUrls:['./message.component.css'],
   changeDetection:ChangeDetectionStrategy.OnPush
})
export class MessageComponent implements OnInit{
   ngOnInit(): void {
       this.typeClass=['upc-message-' + this.msgType];
       this.typeIconClass=[mapping[this.msgType]];
   }
   @Input() msgType:'success' | 'info' | 'warning' | 'error'='info'

   @Input() payload:string = ''

   private typeClass
   private typeIconClass
}

<!--*message.component.html-->
<div class="upc-message">
        <div class="upc-message-content" [ngClass]="typeClass">
            <i class="glyphicon" [ngClass]="typeIconClass"></i>
            {{payload}}
        </div>
</div>

.upc-message {
    position: fixed;
    z-index: 1999;
    width: 100%;
    top: 36px;
    left: 0;
    pointer-events: none;
    padding: 8px;
    text-align: center;
  }
  .upc-message i {
      margin-right: 8px;
      font-size: 14px;
      top: 1px;
      position: relative;
  }
  .upc-message-success i {
      color: green;
  }
  .upc-message-warning i {
      color: yellow;
  }
  .upc-message-error i {
      color: red;
  }
  .upc-message-content {
      padding: 8px 16px;
      -ms-border-radius: 4px;
      border-radius: 4px;
      -webkit-box-shadow: 0 2px 8px #000000;
      -ms-box-shadow: 0 2px 8px #000000;
      box-shadow: 0 2px 8px #000000;
      box-shadow: 0 2px 8px rgba(0,0,0,.2);
      background: #fff;
      display: inline-block;
      pointer-events: all;
  }

ComponentLoader

通过官方文档动态组件一节，可以了解动态创建组件需要通过ComponentFactoryResolver来完成。使用ComponentFactoryResolver创建 ComponentFactory，再通过ComponentFactory的create方法创建组件。看官方文档中API的说明，ComponentFactory的create方法至少需要一个injector参数，而injector的创建在文档中也有提到，其中参数providers为需要注入的类。再梳理下整个过程：

提供providers
创建Injector实例
创建ComponetFactory
使用ComponetFactory创建ComponentRef

//ComponentFactory的create方法
create(injector: Injector, projectableNodes?: any[][], rootSelectorOrNode?: string|any, ngModule?: NgModuleRef<any>): ComponentRef<C>

//使用Injector的create创建injector实例
static create(providers: StaticProvider[], parent?: Injector): Injector

为了代码的复用，这里创建通用的loader类来完成组件的动态创建。其中，attch方法用于初始化ComponetFactory（参数为组件类型）；to方法用于标识组件的父容器；provider方法用于初始化可注入的类；create方法用于创建组件并手动变更检测；remove方法用于移除组件。

import {
    ComponentFactoryResolver,
    ComponentFactory,
    ComponentRef,
    Type,
    Injector,
    Provider,
    ElementRef
} from '@angular/core';
export class ComponentLoader<T>{
    constructor(private _cfr: ComponentFactoryResolver,
        private _injector: Injector) {
    }
    private _componentFactory: ComponentFactory<T>
    attch(componentType: Type<T>): ComponentLoader<T> {
        this._componentFactory = this._cfr.resolveComponentFactory<T>(componentType);
        return this;
    }
    private _parent: Element
    to(parent: string | ElementRef): ComponentLoader<T> {
        if (parent instanceof ElementRef) {
            this._parent = parent.nativeElement;
        } else {
            this._parent = document.querySelector(parent);
        }

        return this;
    }
    private _providers: Provider[] = [];
    provider(provider: Provider) {
        this._providers.push(provider);
    }
    create(opts: {}): ComponentRef<T> {
        const injector = Injector.create(this._providers as any[], this._injector);
        const componentRef = this._componentFactory.create(injector);
        Object.assign(componentRef.instance, opts);
        if (this._parent) {
            this._parent.appendChild(componentRef.location.nativeElement);
        }
        componentRef.changeDetectorRef.markForCheck();
        componentRef.changeDetectorRef.detectChanges();
        return componentRef;
    }
    remove(ref:ComponentRef<T>){
        if(this._parent){
            this._parent.removeChild(ref.location.nativeElement)
        }
        ref=null;
    }
}

同时，为了便于loader的创建，再创建LoaderFactory类，代码如下：

import {
    ComponentFactoryResolver,
    Injector,
    Injectable,
    ElementRef
} from '@angular/core';
import { ComponentLoader } from './component-loader.class';

@Injectable()
export class ComponentLoaderFactory {
    constructor(private _injector: Injector,
        private _cfr: ComponentFactoryResolver) {

    }

    create<T>(): ComponentLoader<T> {
        return new ComponentLoader(this._cfr, this._injector);
    }
}

message service

message service提供显示message的API，代码如下：

import {Injectable,Injector} from '@angular/core';
import { ComponentLoaderFactory } from '../component-loader/component-loader.factory';
import {MessageComponent} from './message.component';
import {ComponentLoader} from '../component-loader/component-loader.class';

@Injectable()
export class MessageService{
    constructor(private _clf:ComponentLoaderFactory,private _injector:Injector){
        this.loader=this._clf.create<MessageComponent>();
    }
    private loader:ComponentLoader<MessageComponent>
    private createMessage(t,c,duration=2000){
        this.loader.attch(MessageComponent).to('body');
        const opts = {
            msgType: t,
            payload:c
        };
        const ref = this.loader.create(opts);
        ref.changeDetectorRef.markForCheck();
        ref.changeDetectorRef.detectChanges();
        let self=this;
        let st = setTimeout(() => {
            self.loader.remove(ref);
            st = null；
        }, duration);
    }
    public info(payload,duration?) {
        this.createMessage('info',payload,duration);
    }
    public success(payload,duration?) {
        this.createMessage('success',payload,duration);
    }
    public error(payload,duration?) {
        this.createMessage('error',payload,duration);
    }
    public warning(payload,duration?) {
        this.createMessage('warning',payload,duration);
    }
}

message.module

最后，增加message.module.ts。记得要把动态创建的组件添加到entryComponents数组中。

import {NgModule} from '@angular/core';
import { CommonModule } from '@angular/common';
import {MessageComponent} from './message.component';
import {MessageService} from './message.service';
import {ComponentLoaderFactory} from '../component-loader/component-loader.factory';

@NgModule({
   imports:[CommonModule],
   declarations:[MessageComponent],
   providers:[MessageService,ComponentLoaderFactory],
   entryComponents:[MessageComponent],
   exports:[MessageComponent]
})
export class MessageModule{
}

使用方法

注入MessageService，调用API使用Message组件。

this._msgService.success('成功了!');