Angular2, evaluate template from string inside a component

Question

It\'s possible evaluate template from string in a variable?. I need place the string in the component instead of the expression, e.g.

template: \"

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Answer 1

You can create your own directive that will do it:

compile.directive.ts

@Directive({
  selector: '[compile]'
})
export class CompileDirective implements OnChanges {
  @Input() compile: string;
  @Input() compileContext: any;

  compRef: ComponentRef<any>;

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

  ngOnChanges() {
    if(!this.compile) {
      if(this.compRef) {
        this.updateProperties();
        return;
      }
      throw Error('You forgot to provide template');
    }

    this.vcRef.clear();
    this.compRef = null;

    const component = this.createDynamicComponent(this.compile);
    const module = this.createDynamicModule(component);
    this.compiler.compileModuleAndAllComponentsAsync(module)
      .then((moduleWithFactories: ModuleWithComponentFactories<any>) => {
        let compFactory = moduleWithFactories.componentFactories.find(x => x.componentType === component);

        this.compRef = this.vcRef.createComponent(compFactory);
        this.updateProperties();
      })
      .catch(error => {
        console.log(error);
      });
  }

  updateProperties() {
    for(var prop in this.compileContext) {
      this.compRef.instance[prop] = this.compileContext[prop];
    }
  }

  private createDynamicComponent (template:string) {
    @Component({
      selector: 'custom-dynamic-component',
      template: template,
    })
    class CustomDynamicComponent {}
    return CustomDynamicComponent;
  }

  private createDynamicModule (component: Type<any>) {
    @NgModule({
      // You might need other modules, providers, etc...
      // Note that whatever components you want to be able
      // to render dynamically must be known to this module
      imports: [CommonModule],
      declarations: [component]
    })
    class DynamicModule {}
    return DynamicModule;
  }
}

Usage:

@Component({
  selector: 'product-item',
  template: `
    <div class="product">
      <ng-container *compile="template; context: this"></ng-container>
    </div>
  `,
})
export class ProductItemComponent {
  @Input() name: string;
  @Input() price: number = 0;
  @Input() template: string = `{{ name }} <b>{{ price | currency }}</b>`;
}

Plunker Example

See also

• Angular 2.1.0 create child component on the fly, dynamically

Answer 2

not sure how you're building the template string

import { ..., OnInit } from '@angular/core';

@Component({
    selector: 'product-item',
    template: `
    <div class="product" [innerHtml]='template_string'>
    </div>`,
    })
export class ProductItemComponent implements OnInit {
    @Input() name: string;
    @Input() price: number = 0;
    @Input() pre: string;
    @Input() mid: string;
    @Input() post: string;
    template_string;
    ngOnInit() {
        // this is probably what you want
        this.template_string = `${this.pre}${this.name}${this.mid}${this.price}${this.post}`
    }
}

<product-item [name]="name" [price]="price" pre="<em>" mid="</em><b>" post="</b>"></product-item>

the string can be built from outside the component, would still recommend something like ngIf to control dynamic templates though.

Answer 3

In Angular double curly braces {{}} are used to evaluation an expression in a component's template. and not work on random strings or dynamically added DOM elements. So one way of doing this is to use typescript string interpolation using ${}. check the rest of code to understand

@Component({
  selector: 'product-item',
  template: `
    <div class="product" [innerHTML]="template"></div>`,
})
export class ProductItemComponent {
  @Input() name: string;
  @Input() price: number = 0;
  @Input() template: string = `${ this.name } <b>${ this.price }}</b>`;
}