angular5 組件之間監聽傳值變化

http://www.cnblogs.com/SLchuck/p/5904000.html

 https://i.cnblogs.com/EditPosts.aspx?postid=7995179&update=1

https://segmentfault.com/a/1190000010048073

agular5 父子組件之間傳值是實用

• 第一類：父子組件間的通信

1. @Input 和@Output

當然一般傳值變化是指父組件像子組件傳的值變化的情況，如地圖zoom變化

當篩選范圍變化時地圖比例尺變化地圖隨着縮放，這是地圖控件就要監聽父組件的篩選范圍值變化

import {
  Component,
  OnInit,
  Input,
  Output,
  EventEmitter,
  OnDestroy,
  ElementRef,
 OnChanges,
  SimpleChanges
} from '@angular/core';


/*import {loader} from './loader';*/
/*import {BAIDU_MAP_STYLE} from './map';*/
/*import any = jasmine.any;*/

declare const BMap: any;

@Component({
  selector: 'app-baidu-map',
  templateUrl: './baidu-map.component.html',
  styleUrls: ['./baidu-map.component.css']
})
export class BaiduMapComponent implements OnInit, OnChanges {

  @Input() address: string = '深圳';
  @Input() apiKey: string = 'sIq3pmhG5n4xVuKQ8eKr1BiV0hsLP2ek';
  @Input() center: any;
  @Input() zoom = 15;
  @Input() enableScrollWheelZoom = false;                                  //鼠標是否可滾動縮放 默認不可以
  @Input() zoomControl = false;                                            //是否有縮放控件   默認沒有


  @Output() getLocation: EventEmitter<any> = new EventEmitter();

  geoAddress = '';

  constructor(private elementRef: ElementRef) {
  }

  ngOnInit() {

    //不需要init because zoom一進來就變化了就觸發onChange函數執行loader去initMap了所以此處不需要loader

    /*  var address = this.geoAddress ? this.geoAddress : this.address;
      loader(this.apiKey, this.initMap.bind(this,address));*/
  }

 ngOnChanges(changes: SimpleChanges) {
    //當zoomlevel改變刷新地圖時marker不需要初始化位最開始定位的
    var address = this.geoAddress ? this.geoAddress : this.address;
    this.loader(this.apiKey, this.initMap.bind(this, address));
  }
}

這樣就可以監聽了（注意標紅的代碼）

1. forwardref(父獲得子實例)

import { Component, Input, EventEmitter, Output,Host,Inject,forwardRef } from '@angular/core';
import{ParentPage} from '../parent/parent';
@Component({
selector: 'page-child',
templateUrl: 'child.html',
})
export class ChildPage {
constructor( @Host() @Inject(forwardRef(() => ParentPage)) app: ParentPage) {
setInterval(() => {
app.i++;
}, 1000);
}
}

 

 

1. @viewChild（父獲得實例）

import {ViewChild, Component } from '@angular/core';
import{ChildPage}from '../child/child';

@Component({
selector: 'page-parent',
templateUrl: 'parent.html',
})
export class ParentPage {
@ViewChild(ChildPage) child:ChildPage;
ngAfterViewInit() {
setInterval(()=> {
this.child.i++;
}, 1000)
}
}

 

共用一個service

subject

eventEmitter