form_warden

A very simple package to help you write robust, reusable and extendable validations to go with your Flutter Forms.

How it works

Building Blocks

Create simple or complex blocks of validation, and compose those building blocks to create flutter validators. Each block will have it's own logic, a set of args to create dynamic validators & specific error messages for each block.

There are simple ones, configurable ones and even you can create validations aligned to the domain of the app.

Creating a warden

A warden will be a collection of validation blocks. Examples of enum & email pattern checking is added below.

Installation

To use this package, add form_warden as a dependency in your pubspec.yaml file.

Usage

Import the package

import 'package:form_warden/form_warden.dart';

Required field (inbuilt-validator)

TextFormField(
    autovalidateMode: AutovalidateMode.onUserInteraction,
    validator: createWarden([Validators.required]),
    decoration: InputDecoration(
        border: OutlineInputBorder(),
        labelText: f.label,
    ),
    onSaved: null,
),

Required email field (using inbuilt validator)

TextFormField(
    autovalidateMode: AutovalidateMode.onUserInteraction,
    validator: createWarden([Validators.required, Validators.email]),
    decoration: InputDecoration(
        border: OutlineInputBorder(),
        labelText: f.label,
    ),
    onSaved: null,
),

Custom validator

ValidatorFunction greaterThanTen = (value) {
    if (value is int && value > 10) {
        return null;
    }
    return "Must be greater than 10";
};

TextFormField(
    autovalidateMode: AutovalidateMode.onUserInteraction,
    validator: createWarden([greaterThanTen]),
    decoration: InputDecoration(
        border: OutlineInputBorder(),
        labelText: f.label,
    ),
    onSaved: null,
)

Club multiple validators together to create robust validators

ValidatorFunction greaterThanTen = (value) {
    if (value is int && value > 10) {
        return null;
    }
    return "Must be greater than 10";
};
ValidatorFunction lessThanHundred = (value) {
    if (value is int && value < 100) {
        return null;
    }
    return "Must be less than 100";
};

TextFormField(
    autovalidateMode: AutovalidateMode.onUserInteraction,
    validator: createWarden([greaterThanTen, lessThanHundred]),
    decoration: InputDecoration(
        border: OutlineInputBorder(),
        labelText: f.label,
    ),
    onSaved: null,
)

Using higher order functions create configurable validators

ValidatorFunction between(int lowerLimit, int upperLimit) {
  ValidatorFunction greaterThanLowerLimit = (dynamic? value) {
    if (value.isEmpty) return null;
    var _v = int.parse(value);
    if (_v > lowerLimit && _v < upperLimit) return null;
    return "Value must be between $lowerLimit and $upperLimit";
  };
  return greaterThanLowerLimit;
}

TextFormField(
    autovalidateMode: AutovalidateMode.onUserInteraction,
    validator: createWarden([between(10, 100)]),
    decoration: InputDecoration(
        border: OutlineInputBorder(),
        labelText: f.label,
    ),
    onSaved: null,
)

License

MIT