When you display error messages you want to make them as understandable as possible such that the user is able to figure out the problem. Example: the error message of a min validator should ideally contain the actual number and the min number allowed. So the message could be like "You have to enter a number bigger than X. You entered Y". Let's see how Formly allows us to display such highly customizable messages.

 

// app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppComponent } from './app.component';
import { ReactiveFormsModule } from '@angular/forms';
import { FormlyModule, FormlyFieldConfig } from '@ngx-formly/core';
import { FormlyMaterialModule } from '@ngx-formly/material';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

import { SharedModule } from './shared/shared.module';
import { DebugComponent } from './shared/debug.component';

// global min error message, you can override by validation.messages.min in field
export function minValidationMessage(err, field: FormlyFieldConfig) {
  return `Please provide a value bigger than ${err.min}. You provided ${err.actual}`;
}

@NgModule({
  declarations: [AppComponent],
  imports: [
    BrowserModule,
    SharedModule,
    ReactiveFormsModule,
    FormlyModule.forRoot({
      validationMessages: [
        {
          name: 'required',
          message: 'This field is required',
        },
        {
          name: 'min',
          message: minValidationMessage,
        },
      ],
    }),
    FormlyMaterialModule,
    BrowserAnimationsModule,
  ],
  providers: [],
  bootstrap: [AppComponent],
})
export class AppModule {}

 

    {
      key: 'age',
      type: 'input',
      templateOptions: {
        type: 'number',
        label: 'Age',
        min: 18, // use global min error message
      },
      // override the global min error message
      validation: {
        messages: {
          min: 'Sorry, you have to be older than 18',
        },
      },
    },