Crafting Robust Forms in Flutter

Crafting Robust Forms in Flutter

Forms are essential for almost any mobile app. They allow us to capture user information, validate the user input, and send that data to a remote server or local database. Forms are critical to the success of our apps, yet they often get overlooked by developers and designers alike.

In this article, we’ll be discussing how to create robust forms with Flutter using an open source package known as formly. Formly is a powerful tool that helps us quickly craft powerful and customizable forms in Flutter. We’ll also be discussing some best practices for designing effective forms and optimizing form performance.

What Is Formly?

Formly is an open-source package that was released by Flutter team member Hillel Coren. It allows us to quickly generate forms from JSON structures. Developers can define a series of fields and associated properties that define how the form should look and behave. It also makes it easy to add custom validation rules and integrate with backend services.

Designing Forms with Formly

Before we dive into the code, let’s discuss some key aspects to consider when designing forms. First, it’s important to think about the user flow. How do you want users to interact with the form? Do you want them to fill out each field one at a time or move quickly through multiple fields?

Another important factor is form length. A lengthy form can become tedious and discourage users from continuing. Try breaking your form up into multiple pages and provide helpful hints and useful tips along the way. Finally, consider adding progress tracking components such as percentage indicators and page numbers.

Defining a Form in Formly

Now that we have a better understanding of how to design our form, let’s jump into the code. To begin, we need to define the form’s structure. This is done using a JSON object, which contains various key/value pairs. For example, here’s a simple form for capturing basic contact details:

{
  "name": {
    "type": "text",
    "label": "Name"
  },
  "email": {
    "type": "text",
    "label": "Email"
  },
  "phone": {
    "type": "text",
    "label": "Phone"
  }
}

Once the form structure has been defined, the next step is to generate the actual form using the Formly widget. This can be done like this:

Formly(
  fields: formStructure,
  onChanged: (data) {
    // Do something with the data
  ),

The Formly widget takes two arguments: fields, which contains the form structure, and onChanged, which is a callback function that can perform an action when the form is updated.

Validating User Input

Validating user input is an important part of any form. Not only does it prevent invalid data from being submitted, but it also provides feedback to users if they enter incorrect data. Formly makes this process easier by allowing us to define custom validations for each field. Here’s an example of defining a maximum length for a text field:

"name": {
  "type": "text",
  "label": "Name",
  "validators": [
    {
      "name": "maxLength",
      "options": {
        "max": 50
      }
    }
  ]
}

Once the validations have been set up, Formly will automatically check the user input and provide feedback if the input is invalid.

Connecting to a Backend Service or Database

Formly also makes it easy to connect our forms to a backend service or database. Once the form is created, we can attach a callback method to the “onSubmitted” field of the Formly widget. This method can then be used to send the form data to the appropriate service.

Conclusion

Forms are essential for almost any mobile application. They allow us to capture user information, validate user input, and send data to a remote server or database. With Formly, creating forms with Flutter is much simpler, as it allows us to quickly generate robust forms with minimal effort. By following best practices and leveraging Formly’s powerful features, we can ensure our forms are optimized for both UX and performance.