Collections Methods

🎯 Mục tiêu: Functional operations trên collections.

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💡 Transform

var numbers = [1, 2, 3, 4, 5];

var doubled = numbers.map((n) => n * 2).toList();  // [2, 4, 6, 8, 10]
var flat = [[1,2], [3,4]].expand((x) => x).toList(); // [1, 2, 3, 4]

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📝 Filter

var numbers = [1, 2, 3, 4, 5, 6];

var evens = numbers.where((n) => n % 2 == 0).toList();  // [2, 4, 6]
var first = numbers.firstWhere((n) => n > 3);  // 4
var last = numbers.lastWhere((n) => n < 5);    // 4

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🔧 Aggregate

var numbers = [1, 2, 3, 4, 5];

numbers.reduce((a, b) => a + b);  // 15
numbers.fold(10, (a, b) => a + b); // 25

numbers.any((n) => n > 3);   // true
numbers.every((n) => n > 0); // true

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🎯 Chaining

var result = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    .where((n) => n % 2 == 0)
    .map((n) => n * n)
    .take(3)
    .toList();  // [4, 16, 36]

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✅ Checklist

• map, where, reduce, fold
• any, every
• Chain multiple operations

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