Filtering items by value inside ngFor without writing Pipes

问题

I have the following Component:

class MyComponent {
  public mode = 'v';
  readonly modes = ['v', 'a', 'd'];
  ....
}

Now I want to use an ngFor to display buttons for all modes in modes except the current mode stored in mode. I have the following code:

<button *ngFor="let othermode of modes">
  {{ othermode }}
</button>

I always want two buttons to be displayed, containing the remaining 2 modes. I tried this:

<button *ngFor="let othermode of modes.filter(elem => elem !== this.mode)">
  {{ othermode }}
</button>

but it isn't working. All questions I saw required to write a custom pipe for this feature, but isn't there any simple way to filter an array of strings, using just the values ?

回答1:

You can use :

<ng-container *ngFor="let othermode of modes">
  <button *ngIf="othermode!=mode">
    {{ othermode }}
  </button>
</ng-container>

回答2:

Use a filter function for filter the data:

filterFunction(your_collection): any[] {  
    return your_collection.filter(i => i.field.value === filterKey);
}

and in the template:

*ngFor="let value of filterFunction(datasource)"

Or use a exist component. See the thread:

https://stackoverflow.com/a/50071762/4332063

回答3:

Use ng-template with ngIf, If you want to iterate the array with condition. Below is the sample code. you can find the working version here

<ng-template ngFor let-othermode [ngForOf]="modes">
<button *ngIf="othermode!=mode">
  {{ othermode }}
</button>
</ng-template>

来源：https://stackoverflow.com/questions/47406804/filtering-items-by-value-inside-ngfor-without-writing-pipes

标签

angular

ngfor