Type Caster #

A lightweight type casting library for Dart with safe conversions and clear error handling.

Features #

• All Dart types: int, double, String, bool, DateTime, List<T>, Set<T>, Map<K,V>
• Simple API: tryAs<T>(), asString(), asInt(), "123".asInt()
• Safe conversions: Clear error messages with context
• Custom types: Register your own type casters

Installation #

Add type_caster to your pubspec.yaml:

dependencies:
  type_caster: ^0.1.0

dart pub get

Usage #

Quick Start #

import 'package:type_caster/type_caster.dart';

// Safe conversions with null return on failure
final int? number = tryInt('123');        // 123
final bool? flag = tryBool('invalid');    // null

// Direct conversions with exception on failure  
final String text = asString(123);        // "123"
final double price = asDouble('99.99');   // 99.99

// Extension methods for fluent API
final int count = "42".asInt();           // 42
final bool isActive = "true".asBool();    // true

Collections & Complex Types #

// Lists from various sources
final numbers = asList<int>('[1,2,3]');           // [1, 2, 3]
final items = "a,b,c".asList<String>();           // ["a", "b", "c"]

// Sets (unique values)
final tags = asSet<String>('red,blue,red');       // {"red", "blue"}

// Maps from JSON strings
final user = asMap<String, dynamic>('{"name":"John","age":30}');

// DateTime with custom patterns
final date = asDateTime('2023-10-15');
final custom = asDateTime('15/10/2023', pattern: 'dd/MM/yyyy');

Error Handling #

try {
  final result = asBool('invalid');
} catch (e) {
  print(e); 
  // Cannot cast String to bool | Message: String value must be either "true" or "false" | Source: "invalid"
}

// Safe with fallback
final flag = asBool('invalid', orElse: () => false);  // false

Custom Types #

Register casters for your own classes:

class User {
  final String name;
  final int age;
  User({required this.name, required this.age});
  factory User.fromJson(Map<String, dynamic> json) => User(
    name: asString(json['name']),
    age: asInt(json['age']),
  );
}

// Register the caster
TypeCasterRegistry.instance.register<User>((value, {orElse}) {
  if (value is Map<String, dynamic>) return User.fromJson(value);
  if (value is String) return User.fromJson(json.decode(value));
  throw CastException(value, 'User');
});

// Now use it anywhere
final user = tryAs<User>('{"name": "John", "age": 30}');

API Reference #

Core Functions #

Basic Types

• asString(), tryString() - String conversion
• asInt(), tryInt() - Integer conversion
• asDouble(), tryDouble() - Double conversion
• asBool(), tryBool() - Boolean conversion
• asDateTime(), tryDateTime() - DateTime conversion

Collections

• asList<T>(), tryList<T>() - List conversion
• asSet<T>(), trySet<T>() - Set conversion
• asMap<K,V>(), tryMap<K,V>() - Map conversion

Advanced

• tryAs<T>() - Generic type casting

Extension Methods #

String Extensions

"123".asInt()                    // 123
"true".asBool()                  // true  
"a,b,c".asList<String>()         // ["a", "b", "c"]
"2023-01-01".asDateTime()        // DateTime object

Collection Extensions

map.get("key")                   // Safe access
list.firstWhereOrNull(test)      // Safe search
set.mapCast((e) => e.toString()) // Transform Set elements

Contributing #

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

License #

This project is licensed under the MIT License - see the LICENSE file for details.

Support #

If you find this package useful, please consider giving it a star on GitHub.

For issues and feature requests, please use the issue tracker.