Flutter Mobile Development · Ders

Girdi Doğrulama Teknikleri

Veri bütünlüğünü sağlamak için form alanlarında doğrulayıcılar, düzenli ifadeler ve özel mantık kullanarak istemci tarafı doğrulama uygulayın.

Girdi Doğrulama Teknikleri, CoddyKit'te ücretsiz bir Flutter Mobile Development dersidir. Bu, 4 dersinin 2. dersidir. Aşağıdan dersin tamamını ücretsiz okuyabilir, sonra tarayıcıda yerleşik kod editörü ve 7/24 yapay zeka koçu ile uygulamalı olarak pratik yapabilirsin. Bu, Flutter Mobile Development öğrenme yolunun bir parçasıdır ve ilerlemeniz web ve CoddyKit uygulaması arasında senkronize olur. Flutter Mobile Development kursu toplamda 4 dersten oluşur.

Bu dersin bazı bölümleri henüz çevrilmemiş olup İngilizce olarak gösterilmektedir.

What is Input Validation?

When users enter data into your app, you need to make sure it's correct and safe. This process is called input validation.

It's crucial for maintaining data quality and preventing errors or security issues, ensuring your application works as expected.

Why Validate User Input?

Validation helps in many ways to create robust and user-friendly applications:

Data Integrity: Ensures data fits expected formats (e.g., email looks like an email).
User Experience: Guides users to enter correct information, reducing frustration.
Security: Prevents malicious input that could exploit your app (e.g., SQL injection).
Business Logic: Ensures data meets specific business rules (e.g., age requirements, unique usernames).

The TextFormField Validator

In Flutter, the TextFormField widget has a special property called validator. This property takes a function that checks the input value.

If the input is invalid, the function should return an error message (a String). If it's valid, it should return null.

Basic Empty Field Check

Let's see a simple validator that checks if a text field is empty. If it is, an error message appears below the field.

Try typing something, then deleting it and submitting to see the error.

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Validation Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Basic Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

class MyCustomForm extends StatefulWidget {
  const MyCustomForm({super.key});

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              decoration: const InputDecoration(
                hintText: 'Enter your name',
                labelText: 'Name',
              ),
              validator: (value) {
                if (value == null || value.isEmpty) {
                  return 'Please enter some text';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Processing Data')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}

Displaying Validation Errors

When a validator function returns a String (an error message), the TextFormField automatically displays this message below the input field in a distinct red color.

This immediate visual feedback helps users understand what went wrong and how to fix it, improving the overall user experience.

Custom Logic: Password Check

You can write any custom logic inside your validator function. Here, we check if a password is at least 6 characters long, which is a common security practice.

This demonstrates how to implement rules beyond simple empty checks.

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Validation Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Custom Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

class MyCustomForm extends StatefulWidget {
  const MyCustomForm({super.key});

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              obscureText: true,
              decoration: const InputDecoration(
                hintText: 'Enter a password',
                labelText: 'Password',
              ),
              validator: (value) {
                if (value == null || value.isEmpty) {
                  return 'Please enter a password';
                }
                if (value.length < 6) {
                  return 'Password must be at least 6 chars';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Password is valid!')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}

Regular Expressions (Regex)

For more complex validation patterns, like checking email formats, phone numbers, or specific alphanumeric sequences, Regular Expressions (Regex) are incredibly powerful.

A regex is a sequence of characters that defines a search pattern. Dart's RegExp class lets you use them easily.

Email Validation with Regex

Here's how to use a simple regular expression to validate an email address format. It checks for a basic pattern: text@text.domain.

Remember, comprehensive email validation can be complex, but this regex provides a good starting point for common formats.

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Regex Validation Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Email Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

class MyCustomForm extends StatefulWidget {
  const MyCustomForm({super.key});

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();
  final RegExp emailRegex = RegExp(
      r"^[a-zA-Z0-9.]+@[a-zA-Z0-9]+\.[a-zA-Z]+"
  );

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              keyboardType: TextInputType.emailAddress,
              decoration: const InputDecoration(
                hintText: 'Enter your email',
                labelText: 'Email',
              ),
              validator: (value) {
                if (value == null || value.isEmpty) {
                  return 'Please enter an email';
                }
                if (!emailRegex.hasMatch(value)) {
                  return 'Please enter a valid email format';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Email is valid!')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}

Triggering Validation Manually

Validation is typically triggered when the user tries to submit the form. You do this by calling _formKey.currentState!.validate() inside an onPressed handler for a button.

This method runs all validators in the Form and returns true if all are valid, false otherwise. You can also use autovalidateMode on the Form widget to validate inputs as they change, as shown in the example.

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Auto Validate Demo',
      home: Scaffold(
        appBar: AppBar(title: const Text('Auto-Validation')),
        body: const MyCustomForm(),
      ),
    );
  }
}

class MyCustomForm extends StatefulWidget {
  const MyCustomForm({super.key});

  @override
  State<MyCustomForm> createState() => _MyCustomFormState();
}

class _MyCustomFormState extends State<MyCustomForm> {
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      // Auto-validate as user types
      autovalidateMode: AutovalidateMode.always,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: TextFormField(
              decoration: const InputDecoration(
                hintText: 'Enter text (min 3 chars)',
                labelText: 'Input',
              ),
              validator: (value) {
                if (value == null || value.length < 3) {
                  return 'Must be at least 3 characters';
                }
                return null;
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 16.0),
            child: ElevatedButton(
              onPressed: () {
                // Manual validation still works
                if (_formKey.currentState!.validate()) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('Input is valid!')),
                  );
                }
              },
              child: const Text('Submit'),
            ),
          ),
        ],
      ),
    );
  }
}

Validation Check

Which of the following are valid ways to implement input validation in Flutter?

Recap: Input Validation

In this lesson, you learned about client-side input validation in Flutter.

We covered why validation is essential for data integrity, user experience, and security.
You used the validator property of TextFormField to define validation rules.
We explored implementing custom logic and using RegExp for complex patterns.
Finally, you saw how to trigger validation using _formKey.currentState!.validate() and autovalidateMode.

Well done! You're now equipped to build more robust and user-friendly forms.

Sıkça Sorulan Sorular

“Girdi Doğrulama Teknikleri” dersi ücretsiz mi?

Evet — “Girdi Doğrulama Teknikleri” dersin tüm metni burada web'de ücretsiz olarak okunabilir. Etkileşimli olarak pratik yapmak (yerleşik kod editörü ve 7/24 yapay zeka koçu) ve Flutter Mobile Development kursunun geri kalanını açmak için CoddyKit PRO'ya yükselt. Flutter Mobile Development kursu toplamda 4 dersten oluşur.

“Girdi Doğrulama Teknikleri” dersinde ne öğreneceğim?

Veri bütünlüğünü sağlamak için form alanlarında doğrulayıcılar, düzenli ifadeler ve özel mantık kullanarak istemci tarafı doğrulama uygulayın. Flutter Mobile Development ile uygulamalı kodu tarayıcıda doğrudan çalıştırarak pratik yaparsın ve 7/24 yapay zeka koçu dersi çalışırken sorularını yanıtlar.

Flutter Mobile Development öğrenmeye başlamak için deneyim gerekli mi?

Önceden deneyim gerekmez. CoddyKit'te Flutter Mobile Development, başlangıçtan ileri seviyeye kadar yapılandırıldığı için buradan başlayabilir veya başından başlayıp kendi hızında ilerleme yapabilirsin. Bu, 4 dersinin 2. dersidir.

“Girdi Doğrulama Teknikleri” dersi ne kadar sürer?

Çoğu CoddyKit dersi yaklaşık 5–10 dakika sürer. Her biri kısa ve etkileşimli olduğu için sabit ilerleme yaparsın ve web ile uygulama arasında tam olarak bıraktığın yerden devam edebilirsin.

Bu Flutter Mobile Development dersinde kod yazıp çalıştırabilir miyim?

Evet. Her Flutter Mobile Development dersi yerleşik bir kod editörü içerir, bu sayede tarayıcıda gerçek kod yazıp çalıştırabilir ve anlık yapay zeka geri bildirimi alırsın — yerel kurulum gerekli değildir.

Bu kursun tüm dersleri

Form Widget'ı ve Denetleyiciler
Girdi Doğrulama Teknikleri
Özel Form Alanları
Odak, Klavye ve Girdi Kullanıcı Deneyimi

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