Angular translate service, interpolate params in nested json

Question

In angular translation service, interpolating params in normal translation json works well. But in nested json, interpolating params is not working.

My JSON:

  "SampleField": {
    "SampleValidation": {
      "MIN": "Value should not be less than {{min}}", 
      "MAX": "Value should not be more than {{max}}", 
    }
  }

My Angular Code:

ngOnInit(): void {
  this.translateService.get('SampleField.Validation', {
    // using hard coded value just as a sample
    min: 0, max: 2000
  }).subscribe(translation => {
    console.log(translation);
  });
}

Expected Output:

{
    MIN: "Value should not be less than 0",
    MAX: "Value should not be greater than 2000"
}

Actual Output:

{
    MIN: "Value should not be less than {{min}}",
    MAX: "Value should not be greater than {{max}}"
}

Answer 1

According to the source of ngx-translate interpolation works only on strings:

export abstract class TranslateParser {
/**
 * Interpolates a string to replace parameters
 * "This is a {{ key }}" ==> "This is a value", with params = { key: "value" }
 * @param expr
 * @param params
 * @returns {string}
 */
abstract interpolate(expr: string | Function, params?: any): string;

This means you might need to use an array of keys instead of a non-leaf element:

this.translateService.get([
    'SampleField.Validation.MIN', 
    'SampleField.Validation.MAX'
  ], {
  // using hard coded value just as a sample
  min: 0, max: 2000
}).subscribe(translation => {
  console.log(translation);
});

Answer 2

You can also do this by using the translate pipe, so that you can remove the additional service dependency to your component.

<p *ngIf="!item?.isRemovable">
{{'i18n.dashboard.heading' 
| translate:{'TEXTTOFIND': 'STRINGTOREPLACE'} }}
</p>

Just make sure that your key i18n.test.key has this TEXTTOFIND interpolated. Something like below.

"heading": "This is with the interpolated {{TEXTTOFIND}} text."

Note the {{}} in the heading string and the STRINGTOREPLACE can be anything you wish.