How can I get public variable value inside @input decorator of type function?

Question

I have a dropdown component which has @Input decoration having function with arguments and it returns boolean value

dropdown-abstract.component.ts

    @Input() public itemDisabled: (itemArgs: { dataItem: any; index: number }) => boolean = () => false;

license-add.component.html

        <hf-shared-dropdown-small class="license-card__row-input"
                                  [id]="'expiryDate'"
                                  [required]="false"
                                  [itemDisabled]="itemDisabled"
                                  [isConfirmable]="false"
                                  [data]="expiryDates"
                                  [value]="selectedExpiryDate"
                                  (valueChange)="dateSelect($event)">
        </hf-shared-dropdown-small>

license-add.component.ts

    public getCustomer(): void {
        this.loading = true;
        this.customerService.getCustomer(this.customerId)
            .pipe(first(), finalize(() => this.loading = false))
            .subscribe((response: CustomerResponse) => {
                if (response && response.success) {
                   
                    this.customerName = response.name;
                    this.registeredTo = response.tradingName ?? response.name;
                    this.locationCount = response.licensedLocCount;
                    this.employeeCount = response.licensedEmpCount;
                    //here we set the contract end date to use
                    this.contractEndDate = response.contractEndDate;
                
                    sessionStorage.setItem("contractEndDate",this.contractEndDate.toString());
                    if (response.contractEndDate && response.contractEndDate > 0) {
                        this.selectedExpiryDate = this.expiryDates[3];
                        this.dateSelect(this.selectedExpiryDate);
                    }
                } else {
                    this.modalService.showInfoPopup({ title: 'Ooops!', text: 'Customer missing.', showIcon: true, popupType: PopupTypes.Error });
                }
            },
                (error: any) => {
                    this.modalService.showInfoPopup({ title: 'Ooops!', text: error, showIcon: true, popupType: PopupTypes.Error });
                });
    }

then @Input function in this component

      public itemDisabled(itemArgs: { dataItem: IdNameValue; index: number; date: number})  {

        console.log(this.contractEndDate)
   
        if ((this.contractEndDate)) {
            if (itemArgs.dataItem.id === LicensePeriod.ContractEndDate) {
                return true;
            }
        }
        return false;
    }

Now when I access the itemDisabled function, this.contractEndDate gives undefined although the value was set earlier.

Answer 1

That is happening in your case because the itemDisabled is being called from another context (and another this).

To resolve it you need to:

• Either change the function to an arrow function instead of a normal function:

public itemDisabled = (itemArgs: {
  dataItem: IdNameValue;
  index: number;
  date: number;
}) => {
  console.log(this.contractEndDate);

  if (this.contractEndDate) {
    if (itemArgs.dataItem.id === LicensePeriod.ContractEndDate) {
      return true;
    }
  }
  return false;
};

• Or bind your function to this related to your component:

<hf-shared-dropdown-small
  class="license-card__row-input"
  [id]="'expiryDate'"
  [required]="false"
  [itemDisabled]="itemDisabled.bind(this)"
  [isConfirmable]="false"
  [data]="expiryDates"
  [value]="selectedExpiryDate"
  (valueChange)="dateSelect($event)"
>
</hf-shared-dropdown-small>

You can read more here about the differences between the arrow function and the normal one: https://stackoverflow.com/a/34361380/15159603

Answer 2

in your license-add.component.html your are giving only [itemDisabled]="itemDisabled"

maybe try to use [itemDisabled]="itemDisabled()" with your itemArgs-Object?

I think the problem is, that you dont use your itemArgs in html