invoke pipe during run time using pipe name /metadata

问题

I'm trying to build a dynamic table where i wand to decide in run time which pipe to use (If Any).

I'm trying to achieve something similar to (Simplified):

export class CellModel {
     public content: any;
     public pipe: string
}

Table

<tbody>
     <tr *ngFor="let row of data">
         <template ngFor let-cell [ngForOf]=row>
           <td *ngIf="cell.pipe">{{cell.content | cell.pipe}}</td>
           <td *ngIf="!cell.pipe">{{cell.content}}</td>
     </tr>
</tbody>

I understand that this example gives an error. Can i use Reflect is some manner or some other solution?

回答1:

You can't apply pipes dynamically. What you can do is to build a "meta" pipe that decides what transformation(s) to do.

@Pipe({
  name: 'meta'
})
class MetaPipe implements PipeTransform {
  transform(val, pipes:any[]) {
    var result = val;
    for(var pipe of pipes) {
      result = pipe.transform(result);
    }
    return result;
  }
}

and then use it like

<td *ngIf="cell.pipe">{{cell.content | meta:[cell.pipe]}}</td>

回答2:

For runtime compile only you can create a directive which will compile template dynamically.

UPDATE:

Using compileModuleAndAllComponentsAsync for RC.6^

dynamic-pipe.ts

  ngAfterViewInit() {
    const data = this.data.content;
    const pipe = this.data.pipe;

    @Component({
      selector: 'dynamic-comp',
      template: '{{ data | ' + pipe  + '}}'
    })
    class DynamicComponent  {
        @Input() public data: any;
    };

    @NgModule({
      imports: [BrowserModule],
      declarations: [DynamicComponent]
    })
    class DynamicModule {}

    this.compiler.compileModuleAndAllComponentsAsync(DynamicModule)
      .then(({moduleFactory, componentFactories}) => {
        const compFactory = componentFactories.find(x => x.componentType === DynamicComponent);
        const injector = ReflectiveInjector.fromResolvedProviders([], this.vcRef.parentInjector);
        const cmpRef = this.vcRef.createComponent(compFactory, 0, injector, []);
        cmpRef.instance.data = data;
      });
  }

Plunker sample RC.6^

OBSOLETE SOLUTION

In RC.5 you can use Compiler.compileComponentSync/Async to do that:

dynamic-pipe.ts

@Directive({
  selector: 'dynamic-pipe' 
})
export class DynamicPipe {
  @Input() data: CellModel;

  constructor(private vcRef: ViewContainerRef, private compiler: Compiler) {}

  ngAfterViewInit() {
    const metadata = new ComponentMetadata({
      template: '{{ data | ' + this.data.pipe  + '}}'
    });

    const data = this.data.content;
    const decoratedCmp = Component(metadata)(class DynamicComponent {  data = data; });

    this.compiler.compileComponentAsync(decoratedCmp)
      .then(factory => {
        const injector = ReflectiveInjector.fromResolvedProviders([], 
           this.vcRef.parentInjector);
        this.vcRef.createComponent(factory, 0, injector, []);
      });
  }
}

And use it this way:

<template ngFor let-cell [ngForOf]="row">
   <td><dynamic-pipe [data]="cell"></dynamic-pipe></td>
</template>

See also the plunker sample RC.5 that demonstrates this feature.

Anyway i think Günter's solution is preferable

来源：https://stackoverflow.com/questions/39252944/invoke-pipe-during-run-time-using-pipe-name-metadata

标签

angular

angular2-pipe