DEV Community: margaret ogbor

Submitting a Dynamic Registration Form with Angular Signal Forms

margaret ogbor — Wed, 15 Jul 2026 08:14:39 +0000

In our previous blog post, we created a Dynamic Form using angular signal forms, that displayed different fields based on the selected account type.
In this blog post we will be looking at how we can submit our data to the backend, transforming our form model into the payload our backend expects, allowing our UI and API to have different data structures when needed.

Why transform our form data?

We designed our registration form based on what our user interface requirements were and not on the shape of our backend API.

export interface userAccount {
  account: {
    type: 'individual' | 'business';
    individual: {
      firstName: string;
      lastName: string;
    },
    business: {
      companyName: string;
      taxId: string;
      registrationNumber: string;
    }
  }
}

But what if our backend expects a totally different shape for our payload? For example:

export interface CreateAccountReq {
  accountType: 'individual' | 'business';
  firstName?: string;
  lastName?: string;
  companyName?: string;
  taxId?: string;
  registrationNumber?: string;
}

Instead of forcing our form model to match our backend request model, Angular recommends that we design our form around our user experience and translate it into what the backend requires, when we are ready to submit our data.

Let's see how we can do that.

Transforming Form Model to Backend Model

First we create a helper function to convert form model to backend api model:

import { CreateAccountReq, userAccount } from '../models/account';

export function formToRequest( form: userAccount ): CreateAccountReq {
  if (form.account.type === 'individual') {
    return {
      accountType: 'individual',
      firstName: form.account.individual.firstName,
      lastName: form.account.individual.lastName,
    }
  }
  return {
    accountType: 'business',
    companyName: form.account.business.companyName,
    taxId: form.account.business.taxId,
    registrationNumber: form.account.business.registrationNumber,
  }
}

Submitting Form Data

Now that our helper function is ready, we make use of Angular Signal Form's submit() function. The submit function is built into the signal forms Api and helps you manage form submission lifecycles.

To submit our registrationForm, we manually create a submit method:

async onSubmit(event: Event) {
    event.preventDefault();
    const success = await submit(this.registerationForm, async (field) => {
      const backendModel = formToRequest(this.field().value());
      const result = await this.fakeBackendService.createAccount(backendModel);
      if (result.ok) return;
      return { kind: 'serverError', message: 'Failed to save' };
    });
    if (success) {
      console.log("Account details submitted Successfully ...")
    }else{
      console.log("Unable to submit data ...")
    }
  }

In angular Signal Forms, since we are not using the template's FormRoot directive to submit the form but using the manual submission:

We prevent the browser's default behavior by using the preventDefault() so we can handle submission ourselves.
We then call the Signal Form's submit() method and pass it two things:
1. The form we intend to submit.
2. A callback that contains the code we want to run.
The submit() function resolves to true if successful submission and false if errors are returned.

NB: The callback passed to submit() will only execute if all fields pass validation. If any validation errors exist, the submission is stopped and the callback will not execute.

🔗 Live Demo & Source Code ⭐

Dynamic Registration Form

References

Dynamic Form Validation with Angular Signal Forms

margaret ogbor — Wed, 08 Jul 2026 11:11:09 +0000

There are times when we might need to work on forms that show and validate fields depending on a users selected input. For example an account registration form, with two types of account:

Individual
Business

When the user selects individual, show:

First name
Last name

When the user selects business, show:

Company name
Tax ID

This means that the validation rules will likely change for every change in account type.

In this blog post, we'll see how we can dynamically validate form fields based on a users selected account type, using angular signal forms.

Setting up our form model

Our form model tells us what our form will look like and the data it will contain. We define it like so:

export interface userAccount {
  account: {
    type: 'individual' | 'business';
    individual: {
      firstName: string;
      lastName: string;
    },
    business: {
      companyName: string;
      taxId: string;
      registrationNumber: string;
    }
  }
}

Creating the `accountModel`

Next, we'll create the accountModel. This holds the initial state of our form.

According to the angular docs, when working with dynamic fields, it is a good idea to initialize every field even if some of them won't be visible initially. Not doing so causes those fields to not exist in the form field tree, making it impossible to reference and interact with them later.

  accountModel = signal<userAccount>({
    account: {
      type: 'individual',
      individual: {
        firstName: '',
        lastName: '',
      },
      business: {
        companyName: '',
        taxId: '',
        registrationNumber: '',
      },
    },
  });

Defining our form schema

Then, we'll tell the form which sections should be visible.
When the user selects Individual, we want to hide the business fields.
When the user selects Business, we want to hide the individual fields.

  accountTypeSchema = schema<userAccount>((user) => {
    // Hide individual account when user selects business.
    hidden(user.account.individual, {
      when: ({ valueOf }) => valueOf(user.account.type) === 'business',
    });
    // Hide business account when user selects individual.
    hidden(user.account.business, {
      when: ({ valueOf }) => valueOf(user.account.type) === 'individual',
    });
  });

Creating our form

Now that we have both our schema and model, we can create the form.
To create the form, we use Angular Signal's form() function, passing both accountModel and accountTypeSchema as arguments.

  registrationForm = form<userAccount>(this.accountModel, this.accountTypeSchema);

At this point, our form is ready to be used in the template.

Building the template

Since our schema already knows which part of the form should be hidden based on a users selected input, we just need to reflect that in the template of our application.
Angular signal forms, expects hidden fields to be removed from the DOM. And that's why we wrapped each section with an @if block statement.
Instead of checking the selected account type, we simply check if the section is hidden.

<form>
  <h2>Create Account</h2>
  <div>
    <label>Account Type</label>

    <div>
      <label>
        <input
          type="radio"
          value="individual"
          [formField]="registrationForm.account.type"
        />
        Individual
      </label>

      <label>
        <input
          type="radio"
          value="business"
          [formField]="registrationForm.account.type"
        />
        Business
      </label>
    </div>
  </div>

  @if (!registrationForm.account.individual().hidden()) {
    <fieldset>
      <legend>Individual Information</legend>

      <div>
        <label for="firstName">First Name</label>
        <input
          id="firstName"
          type="text"
          [formField]="registrationForm.account.individual.firstName"
        />
      </div>

      <div>
        <label for="lastName">Last Name</label>
        <input
          id="lastName"
          type="text"
          [formField]="registrationForm.account.individual.lastName"
        />
      </div>
    </fieldset>
  }

  @if (!registrationForm.account.business().hidden()) {
    <fieldset>
      <legend>Business Information</legend>

      <div>
        <label for="companyName">Company Name</label>
        <input
          id="companyName"
          type="text"
          [formField]="registrationForm.account.business.companyName"
        />
      </div>

      <div>
        <label for="taxId">Tax ID</label>
        <input
          id="taxId"
          type="text"
          [formField]="registrationForm.account.business.taxId"
        />
      </div>

      <div>
        <label for="registrationNumber">Registration Number</label>
        <input
          id="registrationNumber"
          type="text"
          [formField]="registrationForm.account.business.registrationNumber"
        />
      </div>
    </fieldset>
  }

  <button type="submit">Create Account</button>
</form>

When you run the application, you can see that switching between individual and business types automatically updates the visible section of the form with no data lost.

🔗 Live Demo & Source Code ⭐

Dynamic Form Validation with Angular Signal Forms

DEV Community: margaret ogbor

Submitting a Dynamic Registration Form with Angular Signal Forms

Why transform our form data?

Transforming Form Model to Backend Model

Submitting Form Data

🔗 Live Demo & Source Code ⭐

References

Dynamic Form Validation with Angular Signal Forms

Setting up our form model

Creating the accountModel

Defining our form schema

Creating our form

Building the template

🔗 Live Demo & Source Code ⭐

References

Creating the `accountModel`