pattern(pattern: RegExp): (modelValue: any, viewValue: any): boolean

Accepts a pattern and returns a function that, when provided a model value and view value, returns true if the view value matches the pattern.

Parameters:

Returns:

Function - Validator function.

Example:

import app from 'app';

import {
  pattern
} from '@darkobits/formation-validators';

function MyCtrl() {
  const vm = this;

  vm.controls = {
    name: {
      validators: {
        pattern: pattern(/^[\D]+$/g)
      },
      errors: [
        ['pattern', 'Names may only contain letters and punctuation.']
      ]
    }
  };
});

app.component('myComponent', {
  controller: MyCtrl,
  controllerAs: 'vm',
  // ...
});

Why does this validator test against view values?

It is most common to validate the actual input received from the user rather than the value written to the data model. In most cases, the view value and model value for a control are the same. However, when parsers and formatters are used to transform between view values and model values, they can be different.

Imagine you are collecting a user's phone number. You may want to store the number in the E.164 format, but ask the user to enter it in a format appropriate for their locale. In such a case, a $parser would be used to transform the locale-specific view value into an E.164-formatted model value. We want to ensure that the user entered their phone number in the locale-specific format, meaning we need to test the view value, not the model value.