darlin 1.0.1

A comprehensive Dart package that provides Kotlin-like utilities and extensions for enhanced null safety, string manipulation, list operations, boolean logic, and scope functions.

Dart Utilities - Kotlin-like Extensions

A Dart package that provides Kotlin-like utilities and extensions, bringing familiar null safety checks and scope functions to Dart projects.

Features

• String Null Safety Checks: isNullOrEmpty, isNullOrBlank, isNotNullOrEmpty, isNotNullOrBlank
• String Utilities: reversed, capitalize(), isNumeric, isEmail, removeWhitespaces(), limit()
• List Null Safety Checks: isNullOrEmpty, isNotNullOrEmpty
• List Utilities: firstOrNull(), lastOrNull(), singleOrNull(), distinctBy(), takeIf(), takeUnless(), filterNotNull(), mapNotNull()
• Nullable Utilities: isNull, isNotNull, ifNull(), ifNotNull()
• Boolean Utilities: toggle(), xor(), and(), or()
• Scope Functions: let, also, apply for any object type
• Null-safe: All functions are designed with Dart's null safety in mind
• Type-safe: Full type safety with generics support
• Lightweight: Minimal dependencies, focused functionality

Getting started

Add this package to your pubspec.yaml:

dependencies:
  darlin: ^1.0.0

Then import the package:

import 'package:darlin/darlin.dart';

Usage

String Null Safety Checks

String? nullableString = null;
String? emptyString = '';
String? blankString = '   ';
String? normalString = 'Hello, World!';

// Check for null or empty
print(nullableString.isNullOrEmpty); // true
print(emptyString.isNullOrEmpty); // true
print(normalString.isNullOrEmpty); // false

// Check for null or blank (whitespace only)
print(nullableString.isNullOrBlank); // true
print(blankString.isNullOrBlank); // true
print(normalString.isNullOrBlank); // false

// Opposite checks
  print(normalString.isNotNullOrEmpty); // true
  print(normalString.isNotNullOrBlank); // true

String Utilities

final testString = 'hello world';
final numericString = '12345';
final emailString = '[e-mail]';

// String manipulation
print(testString.reversed); // 'dlrow olleh'
print(testString.capitalize()); // 'Hello world'
print(testString.removeWhitespaces()); // 'helloworld'

// Validation
print(numericString.isNumeric); // true
print(emailString.isEmail); // true

// Truncation
final longString = 'This is a very long string';
  print(longString.limit(10)); // 'This is a...'

List Null Safety Checks

List<int>? nullableList = null;
List<int>? emptyList = [];
List<int>? normalList = [1, 2, 3];

print(nullableList.isNullOrEmpty); // true
print(emptyList.isNullOrEmpty); // true
print(normalList.isNullOrEmpty); // false
print(normalList.isNotNullOrEmpty); // true

List Utilities

final numbers = [1, 2, 3, 4, 5];
final mixedList = [1, null, 2, null, 3];
final stringNumbers = ['1', '2', 'abc', '3'];

// Safe element access
print(numbers.firstOrNull()); // 1
print(numbers.lastOrNull()); // 5
print([42].singleOrNull()); // 42

// Filtering and transformation
final evenNumbers = numbers.takeIf((n) => n % 2 == 0); // [2, 4]
final oddNumbers = numbers.takeUnless((n) => n % 2 == 0); // [1, 3, 5]
final nonNullElements = mixedList.filterNotNull(); // [1, 2, 3]
final parsedNumbers = stringNumbers.mapNotNull((s) => int.tryParse(s)); // [1, 2, 3]

// Distinct by property
final people = [Person('John', 25), Person('Jane', 25), Person('Bob', 30)];
final distinctByAge = people.distinctBy((p) => p.age); // [John(25), Bob(30)]

Nullable Utilities

String? nullableValue = null;
String? nonNullValue = 'hello';
int? nullableNumber = 42;

// Null checks
print(nullableValue.isNull); // true
print(nonNullValue.isNotNull); // true

// Default values
final result1 = nullableValue.ifNull('default'); // 'default'
final result2 = nonNullValue.ifNull('default'); // 'hello'

// Conditional execution
nullableValue.ifNotNull((value) => print('This won\'t print'));
nonNullValue.ifNotNull((value) => print('Value is: $value')); // Value is: hello
nullableNumber.ifNotNull((value) => print('Number is: $value')); // Number is: 42

Boolean Utilities

// Toggle boolean value
bool flag = true;
flag = flag.toggle(); // false
flag = flag.toggle(); // true

// Nullable boolean operations
bool? a = true;
bool? b = false;
bool? c = null;

// XOR operations
print(a.xor(b)); // true
print(a.xor(a)); // false
print(a.xor(c)); // null

// AND operations
print(a.and(b)); // false
print(a.and(a)); // true
print(a.and(c)); // null

// OR operations
print(a.or(b)); // true
print(b.or(b)); // false
print(a.or(c)); // null

// Complex expressions
final result = a.and(b).or(a); // true

Scope Functions

let - Transform and return result

String? nullableString = 'hello world';
final upperCaseResult = nullableString.let((it) => it.toUpperCase());
print(upperCaseResult); // "HELLO WORLD"

// Returns null if the object is null
String? nullString = null;
final result = nullString.let((it) => it.toUpperCase());
print(result); // null

also - Side effects, return original object

final numbers = <int>[1, 2, 3];
final result = numbers.also((it) {
  print('Processing list with ${it.length} items');
  it.add(4);
});
print(result); // [1, 2, 3, 4]

apply - Configure object, return original object

class Person {
  String name;
  int age;
  Person(this.name, this.age);
}

final person = Person('John', 25);
final configuredPerson = person.apply((it) {
  it.name = 'Jane';
  it.age = 30;
});
print('${configuredPerson.name}, ${configuredPerson.age}'); // "Jane, 30"

Real-world Example

// Process user input with null safety
String? userInput = '  [e-mail]  ';

final processedEmail = userInput
    .let((it) => it.trim())
    ?.also((it) => print('Processing email: $it'))
    ?.let((it) => it.toLowerCase())
    ?.apply((it) => print('Final email: $it'));

print(processedEmail); // "[e-mail]"

API Reference

StringChecks Extension

Method	Description	Returns
isNullOrEmpty	Returns true if string is null or empty	bool
isNullOrBlank	Returns true if string is null or contains only whitespace	bool
isNotNullOrEmpty	Returns true if string is not null and not empty	bool
isNotNullOrBlank	Returns true if string is not null and contains non-whitespace characters	bool

StringUtils Extension

Method	Description	Returns
reversed	Returns the reversed string	String
capitalize()	Capitalizes the first character of the string	String
isNumeric	Returns true if string contains only numeric characters	bool
isEmail	Returns true if string is a valid email address	bool
removeWhitespaces()	Removes all whitespace characters from the string	String
limit(int maxLength)	Safely truncates string to specified length with '...'	String

ListChecks Extension

Method	Description	Returns
isNullOrEmpty	Returns true if list is null or empty	bool
isNotNullOrEmpty	Returns true if list is not null and not empty	bool

ListUtils Extension

Method	Description	Returns
firstOrNull()	Returns the first element or null if list is empty	T?
lastOrNull()	Returns the last element or null if list is empty	T?
singleOrNull()	Returns the single element or null if list is empty or has multiple elements	T?
distinctBy<K>(K Function(T) selector)	Returns list with distinct elements based on selector function	List<T>
takeIf(bool Function(T) predicate)	Returns elements that satisfy the predicate	List<T>
takeUnless(bool Function(T) predicate)	Returns elements that do not satisfy the predicate	List<T>
filterNotNull()	Returns list containing all non-null elements	List<T>
mapNotNull<R>(R? Function(T) transform)	Returns list containing only non-null transformed elements	List<R>

NullableUtils Extension

Method	Description	Returns
isNull	Returns true if the object is null	bool
isNotNull	Returns true if the object is not null	bool
ifNull(T fallback)	Returns the object if not null, otherwise returns fallback	T
ifNotNull(void Function(T) action)	Executes the function if the object is not null	void

BooleanUtils Extension

Method	Description	Returns
toggle()	Returns the opposite of the current boolean value	bool

NullableBooleanUtils Extension

Method	Description	Returns
xor(bool? other)	Performs XOR operation, returns null if either operand is null	bool?
and(bool? other)	Performs AND operation, returns null if either operand is null	bool?
or(bool? other)	Performs OR operation, returns null if either operand is null	bool?

ScopeFunctions Extension

Method	Description	Returns
let<R>(R Function(T it) block)	Executes function if not null, returns result	R?
also(void Function(T it) block)	Executes function if not null, returns original object	T?
apply(void Function(T it) block)	Executes function if not null, returns original object	T?

Testing

Run the tests to verify functionality:

dart test

Example

See the complete example in example/kotlin_like_utils_example.dart:

dart run example/kotlin_like_utils_example.dart

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License.