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: "<div>{{ template_string }}</div>"

template_string contains: <b>{{ name }}</b>

and all should be evaluated to <div><b>My Name</b></div>

but I see <div>{{ template_string }}</div>

I need something like {{ template_string | eval }} or something else to evaluate the content of the variable on current context.

It's possible? I need something to use this approach because template_string can be changed when the component is used.

Edit1:

Angular Version: 4.0.3

E.g.

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

Usage:

<product-item [name]="product.name" [price]="product.price"></product-item>

Expected: Product Name USD3.00

Output: {{ name }} <b>{{ price | currency }}</b>

does not work, tested with 4.0.3, output the string as is: <div>{{ template_string }}</div> — rafrsr
– rafrsr, Commented May 19, 2017 at 20:15
not, suppose JIT, I'm currently running whit npm start. I'm a beginner, this is my first project using angular2. — rafrsr
– rafrsr, Commented May 19, 2017 at 22:21

Community · Accepted Answer · 2017-05-23 12:10:41Z

19

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

3 Comments

rafrsr Over a year ago

Thanks!! again ;)

zxz Over a year ago

This solution seems to break if the compile directive is used more than once? Any components I declare in the declarations of the dynamic module will be loaded in two modules with the same name, and the compilation crashes.

yurzui Over a year ago

@zxz stackoverflow.com/questions/39678963/…

tesgo · Accepted Answer · 2017-05-20 02:22:13Z

0

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.

edited May 20, 2017 at 2:22

answered May 19, 2017 at 23:22

tesgo

661 silver badge7 bronze badges

1 Comment

rafrsr Over a year ago

it's not my use case, I really need evaluate from string, see: stackoverflow.com/q/44073940/4724040, it's a similar unresolved use case

Khurram · Accepted Answer · 2017-05-20 04:15:30Z

0

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>`;
}

answered May 20, 2017 at 4:15

Khurram

6956 silver badges16 bronze badges

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