angular - 单击关闭按钮时无法设置未定义的属性-角度材料日期

Question

我正在尝试清除日期字段，用户必须手动输入日期。我正在使用角度日期材料。

这是我的错误

这是我的html代码。

<div *ngFor="let item of dialogData?.milestoneData?.maintenanceCountryAssumption; let mcaIndex=index">
<div *ngFor="let element of item.trialDesignElement; let elementIndex=index;">
    {{item.trialDesignElement}}
    <div class="row">
        <div class="col-md-4">
            {{ element.trialName}}
        </div>
        <div class="col-md-4">
            <mat-form-field *ngIf="element.firstPatientInDate">
                <input [disabled]="!enableEdit"
                    (dateChange)="setChange(mcaIndex, elementIndex,'firstPatientInDate', $event)" matInput
                    [matDatepicker]="fpd" placeholder="Choose a date"
                    [value]="getData(element.firstPatientInDate)" name="{{elementIndex}}--{{mcaIndex}}">
                <button mat-button *ngIf="element.firstPatientInDate" matSuffix mat-icon-button
                    aria-label="Clear" (click)="clearFirstDateField(mcaIndex, elementIndex)">
                    <mat-icon>close</mat-icon>
                </button>
                <mat-datepicker-toggle matSuffix [for]="fpd"></mat-datepicker-toggle>
                <mat-datepicker #fpd></mat-datepicker>
            </mat-form-field>
            <mat-form-field *ngIf="!element.firstPatientInDate">
                <input (dateChange)="setChange(mcaIndex, elementIndex,'firstPatientInDate', $event)" matInput
                    [matDatepicker]="dup" placeholder="Choose a date" name="{{elementIndex}}--{{mcaIndex}}"
                    [(ngModel)]="element.firstPatientInDate">
                <button mat-button *ngIf="element.firstPatientInDate" matSuffix mat-icon-button
                    aria-label="Clear" (click)="clearSecondDateField(mcaIndex, elementIndex)">
                    <mat-icon>close</mat-icon>
                </button>
                <mat-datepicker-toggle matSuffix [for]="dup"></mat-datepicker-toggle>
                <mat-datepicker #dup></mat-datepicker>
            </mat-form-field>
        </div>
        <div class="col-md-4">
            <mat-form-field *ngIf="element.lastPatientInDate">
                <input [disabled]="!enableEdit" required [ngClass]="{'lpiError': element.lpiError}" matInput
                    [matDatepicker]="dup3" [min]="dateFilter(element.firstPatientInDate)"
                    name="{{elementIndex+1}}--{{mcaIndex}}" placeholder="Choose a date"
                    [value]="getData(element.lastPatientInDate)">
                <button mat-button *ngIf="element.lastPatientInDate" matSuffix mat-icon-button
                    aria-label="Clear" (click)="clearLPIFirstDateField(mcaIndex, elementIndex);">
                    <mat-icon>close</mat-icon>
                </button>
                <mat-datepicker-toggle matSuffix [for]="dup3"></mat-datepicker-toggle>
                <mat-datepicker #dup3></mat-datepicker>
            </mat-form-field>
            <mat-form-field *ngIf="!element.lastPatientInDate">
                <input required [ngClass]="{'lpiError': element.lpiError}"
                    (dateChange)="setChange(macIndex, elementIndex,'lastPatientInDate', $event)" matInput
                    [matDatepicker]="dup4" [min]="dateFilter(element.firstPatientInDate)"
                    name="{{elementIndex+1}}--{{mcaIndex}}" placeholder="Choose a date"
                    [(ngModel)]="element.lastPatientInDate">
                <button mat-button *ngIf="element.lastPatientInDate" matSuffix mat-icon-button
                    aria-label="Clear" (click)="clearLPISecondDateField(mcaIndex, elementIndex);">
                    <mat-icon>close</mat-icon>
                </button>
                <mat-datepicker-toggle matSuffix [for]="dup4"></mat-datepicker-toggle>
                <mat-datepicker #dup4></mat-datepicker>
            </mat-form-field>

        </div>
    </div>
</div>

这是我的 ts 代码。

clearFirstDateField(mcaIndex, elementIndex) {
this.dialogData.milestoneData.maintenanceCountryAssumption[mcaIndex].trialDesignElement[elementIndex].
firstPatientInDate = '';

}

实际上我得到了错误*ngIf="element.firstPatientInDate"

在控制台中我可以看到 FPID

请让我知道我在这里做错了什么。