行为主体未更新异步管道

Question

我正在尝试使用行为主题在HTML中提供异步管道。该对象在初始加载时起作用，但随后在任何后续尝试更新时都不会注册发射。我无法弄清楚的是，为什么接下来在行为主题上没有从switchMap触发apiCall（）。

buy-plans.component.html

int main()
{
    FILE* p;
    p = fopen("file.txt", "r+");

    int i = 0, j, k;
    char* pointer, lineRead[20], arr2[20][20];
    if (p != NULL)
    {
        while (!feof(p))
        {
            fscanf(p, "%s", &lineRead);
            for (k = 0; lineRead[k] != '\0'; k++);
            pointer = lineRead;
            for (j = 0; j < k; j++)
            {
                arr2[i][j] = *pointer;
                pointer++;
            }
            arr2[i][j] = '\0';
            i++;
        }
        for (int i = 0; i < 4; i++)
        {
            printf("%s\n", arr2[i]);
        }
    }
    else
    {
        printf("Couldn't find file.\n");
    }
    return 0;
}

buyplans.component.ts

<div class="wrapper" *ngIf="buyPlan$ | async as buyPlan; else loading">
     <div class="desktop-container" *ngIf="deviceInfoService.isDesktopDevice; else mobileContainer">
         <app-buy-plans-desktop [buyPlan]="buyPlan"> </app-buy-plans-desktop>
     </div>
     <ng-template #mobileContainer>
         <app-buy-plans-mobile [buyPlan]="buyPlan"></app-buy-plans-mobile>
     </ng-template>
</div>

<ng-template #loading>
      <div class="spinner-wrapper" [ngClass]="{ 'sidenav-open': sharedService.isSidenavOpen$ | async }">
          <div class="spinner-mask"></div>
              <mat-spinner class="buy-plans-spinner" color="accent"></mat-spinner>
          </div>
</ng-template>