从 Angular 中的孙组件访问祖父组件属性

Question

I'm building an Angular application and need to access a property of Component 1 in Component 3. The relationship between component 1 and component 3 is grandparent-grandchild.

I've successfully implemented communication between parent/child components directly (ie from component 1 to component 2 and from component 2 to component 3 (note that component 3 is the child of component 2 and component 2 is the child of component 1). I only need one-way communication (ie accessing properties from (grand)parent-components in the child-component).

Below you can see the structure of my application. I also make use of shared services.

Component 1.ts

import { Component, OnInit } from '@angular/core'
import { StrategyService } from './shared/strategy.service'

@Component({
    selector: 'strategies-list',
    templateUrl: './strategies-list.component.html'        
})

export class StrategiesListComponent implements OnInit {
    strategies:any[]
    constructor(private strategyService: StrategyService) {

    }

    ngOnInit() {
        this.strategies = this.strategyService.getStrategies()
    }

}

Component 1.html

<div>
<h1>Strategies</h1>
<hr/>
<strategy-thumbnail *ngFor = "let strategy of strategies" [strategy] = "strategy">  </strategy-thumbnail> 
</div>

Component 2.ts

import { StrategyService } from './shared/strategy.service'


@Component ({
    selector:'strategy-thumbnail',
    templateUrl:'./strategy-thumbnail.component.html',
    styles: [`
        .pad-left { margin-left: 10px; }
        .well div { color: #bbb; }
        `]
})

export class StrategyThumbnailComponent implements OnInit {
    @Input() strategy:any
    psets:any

    constructor(private strategyService: StrategyService) {

    }

    ngOnInit() {
        this.psets =this.strategyService.getParameterSets(this.strategy.Name)
    }



}

Component 2.html

<div class="well">
    {{strategy?.Name}}
    <param-set *ngFor = "let pset of psets" [pset] = "pset"> </param-set>

</div>

Component 3.ts

import { Component, Input, OnInit } from '@angular/core'
import { StrategyService } from '../strategies/shared/strategy.service'




@Component ({
    selector:'param-set',
    templateUrl:'./param-set.component.html'
})

export class ParamSetComponent {
    @Input() pset: any
    @Input() strategy: any
    returns: any




    constructor(private strategyService: StrategyService) {

    }

    ngOnInit() {

        this.returns = this.strategyService.getReturns(***SomeStrategyName***,this.pset.Name)
    }


}

Component 3.html

<div> {{pset?.Name}} </div>


<return-vector *ngFor = "let return of returns" [return] = "return"> </return-vector>

Component 4.ts

import { Component, Input } from '@angular/core'



@Component ({
    selector:'return-vector',
    templateUrl:'./return-vector.component.html'
})

export class ReturnVectorComponent {
    @Input() strategy:any
    @Input() pset: any
    @Input() return: any
}

Component 4.html

<div>Period: {{return?.period}}, Return: {{return?.return}}</div>

strategy.service.ts

import { Injectable } from '@angular/core'


@Injectable()

export class StrategyService {
    getStrategies() {
        return STRATEGIES
    }

    getStrategy(Name:string) {
        return this.getStrategies().find(strat => strat.Name === Name)
    }

    getParameterSets (Name: string) {
        return this.getStrategy(Name).PSETS
    }

    getParameterSet (StrategyName, PSetName) {
        return this.getParameterSets(StrategyName).find(pset => pset.Name === PSetName)
    }

    getReturns (StrategyName, PSetName) {
        return this.getParameterSet(StrategyName, PSetName).Returns
    }

    getReturn(StrategyName, PSetName, Period) {
        return this.getReturns(StrategyName, PSetName).find(returnperiod => returnperiod.period === Period)
    }

}

const STRATEGIES = [
    { "Name": "SomeStrategyName1", "PSETS: [{"Name":"SomePSetName1", "Returns": [{ "period": "someperiod1", "return" : somenumber1}, {"period": "someperiod2", "return" : somenumber2}]}, {"Name":"SomePSetName2", "Returns": [{ "period": "someperiod3", "return" : somenumber3}, {"period": "someperiod4", "return" : somenumber4}]}]},

{ "Name": "SomeStrategyName2", "PSETS: [{"Name":"SomePSetName3", "Returns": [{ "period": "someperiod5", "return" : somenumber5}, {"period": "someperiod6", "return" : somenumber6}]}, {"Name":"SomePSetName4", "Returns": [{ "period": "someperiod3", "return" : somenumber3}, {"period": "someperiod4", "return" : somenumber4}]}]},

...

{ "Name": "SomeStrategyNameK", "PSETS: [{"Name":"SomePSetName3", "Returns": [{ "period": "someperiod5", "return" : somenumber5}, {"period": "someperiod6", "return" : somenumber6}]}, {"Name":"SomePSetName4", "Returns": [{ "period": "someperiod3", "return" : somenumber3}, {"period": "someperiod4", "return" : somenumber4}]}]}]

In the code above, everything works as expected apart from one thing: in component 3.ts I want to access some specific return set. If I input some specific strategy name (eg "SomeStrategyName1"), my code works. But I want this strategy name to be specific to the strategies I'm looping through.

I've tried replacing "SomeStrategyName1" with this.strategy.Name since I've used the input parameter twice (once in component 3 and once in component 2). In component 2, this works: I can successfully access the Name property of this.strategy when calling the getParameterSets function in the ts-file.

In Component 3 however, this does not work. I get a TypeError: Cannot read property 'Name' of undefined at ParamSetComponent.ngOnInit.

Answer 1

You need to pass strategy in Component 2 Template to param-set component as it expects one:

<div class="well">
  {{strategy?.Name}}
  <param-set 
    *ngFor="let pset of psets" 
    [pset]="pset" 
    [strategy]="strategy">
  </param-set>
</div>

You'll also have to do the same for Component 3 and so on...

<div> {{pset?.Name}} </div>
<return-vector 
  *ngFor="let return of returns" 
  [pset]="pset"
  [strategy]="strategy"
  [return]="return">
</return-vector>