在 Angular 中將數據從父組件傳遞到子組件時出現 HTML 錯誤

Question

在這里，我將數據從父母傳遞給孩子，並嘗試使用這些數據繪制圖表。 這是我在子組件createGraph(divName, chartDataInfo)中的圖形繪制方法。在這里我試圖繪制 2 個圖表。

  export class ViewComponent implements OnInit{
      lineChart = ['line_chart1', 'line_chart2', 'line_chart3'];
      value = ['33.5M', '67.9M', '90.9M', '09.9M'];
      names = ['Bookings', 'Modifications','cancellations',  'Revenue' ];
      bookingInfo = [];
      mdfInfo = [];
    
      ngOnInit() {
         this.getInfo();
         this.getBookingInfo();
        }
    
      getBookingInfo() {
              const params = [];
              params.push({code: 'dateType', name: 'BOOKING'});
              params.push({code: 'fromDate', name: '2019-01-01'});
              params.push({code: 'toDate', name: '2019-12-31'});
    
              this.ServiceHandler.getTxnInfo([], params).subscribe(
                bookings => {
                  this.bookingInfo = bookings.responseObj.txnValues;
                  console.log(this.bookingInfo);
              });
          }
    
       getInfo(){
        const params = [];
        params.push({code: 'fromDate', name: '2019-01-01'});
        params.push({code: 'toDate', name: '2019-12-31'});
        this.ServiceHandler.getMdfInfo([], params).subscribe(
          modifications => {
            this.mdfInfo = modifications.responseObj.txnValues;
            this.modificationTtcSum = modifications.responseObj.ttcSum;
           });
      }
    
    }

這是我的dashboard.component.html

<app-chips [lineChart]="lineChart[0]" [value] = "value[0]" [name] = "names[0]" [mdfInfo] = "mdfInfo"></app-summary-chips>
<app-chips [lineChart]="lineChart[1]" [value] = "value[1]" [name] = "names[1]" [bookingInfo] = "bookingInfo"></app-summary-chips>

這是我的子組件。 因此我調用了this.createGraph(this.lineChart, this.mdfInfo); 在ngOnChanges(changes: SimpleChanges)內 2 次。但是當我喜歡這兩個圖表時都不會出現。當我在ngOnChanges(changes: SimpleChanges)和同時調用this.createGraph(this.lineChart, this.mdfInfo)只有一次我只使用一次<app-summary-chips>選擇器，然后繪制一個圖表。 原因是什么？

export class ChipsComponent implements OnInit {
  @Input('lineChart') lineChart: string;
  @Input('value') value: string;
  @Input('name') name: string;
  @Input() bookingInfo = [];
  @Input()  mdfInfo = [];

  ngOnChanges(changes: SimpleChanges) {
    console.log(this.bookingInfo);
    console.log(this.mdfInfo );
    this.createGraph(this.lineChart, this.mdfInfo);
    this.createGraph(this.lineChart, this.bookingInfo);
    }

   createGraph(divName, chartDataInfo) {
    am4core.useTheme(am4themesAnimated);
  
    const chartNameChartTTV = am4core.create(divName, am4charts.XYChart);
    chartNameChartTTV.width = am4core.percent(100);
    chartNameChartTTV.height = am4core.percent(100);
    console.log(this.bookingInfo);
    chartNameChartTTV.padding(0, 0, 0, 0);
    chartNameChartTTV.data = [];

    for (let i = 0; i < chartDataInfo.length; i++) {
      const booking = chartDataInfo[i];
      console.log(booking);
      chartNameChartTTV.data.push({date: booking.time, value: booking.ttc});
    }

    chartNameChartTTV.colors.list = [
      am4core.color('rgba(4, 69, 142, 1)'),
    ];

    // Create axes
    const dateAxis = chartNameChartTTV.xAxes.push(new am4charts.DateAxis());
    const valueAxis = chartNameChartTTV.yAxes.push(new am4charts.ValueAxis());

    valueAxis.renderer.grid.template.disabled = true;
    valueAxis.renderer.labels.template.disabled = true;
    dateAxis.renderer.grid.template.disabled = true;
    dateAxis.renderer.labels.template.disabled = true;

// Create series
    const series = chartNameChartTTV.series.push(new am4charts.LineSeries());
    series.dataFields.valueY = 'value';
    series.dataFields.dateX = 'date';
    series.tooltipText = '{value';
    series.fillOpacity = 1;
    series.strokeWidth = 2;
    series.minBulletDistance = 15;
  
  }

}

這是我的chips.component.html

<div class="l-content-wrapper c-summary-chip oh" >
  <div class="c-summary-chip__value">{{value}}</div>
  <div class="c-summary-chip__txt">{{name}}</div>
  <div id= "{{lineChart}}" class="c-summary-chip__graph ">
  </div>
</div> 

Answer 1

嘗試將代碼包裝在 if 檢查中

createGraph(divName, chartDataInfo) {

    if (divName && chartDataInfo.length) {}
}

由於 ngOnChanges 是一個異步事件，因此無法保證當您調用 function 內部更改時，所有參數都會出現。

也為了調試給 console.log 像這樣。

createGraph(divName, chartDataInfo) {
    console.log(divName, chartDataInfo);

    if (divName && chartDataInfo) {}
}

這樣，您可以在調用 function 時確認所有需要的數據。

Answer 2

在ngOnChanges鈎子中使用SimpleChanges來跟蹤您的input參數。 如果參數存在，請致電您的 function。

ngOnChanges(changes: SimpleChanges): void {
    if (changes['divName'] && changes['chartDataInfo']) {
        this.createGraph(changes['divName'].currentValue, changes['chartDataInfo'].currentValue);
    }
}

請看一下https://dev.to/nickraphael/ngonchanges-best-practice-always-use-simplechanges-always-1feg