Null-aware Operators

🎯 Mục tiêu: Operators để xử lý null values.

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💡 Các operators

String? name;

// ?. - null-aware access
print(name?.length);  // null (không crash)

// ?? - null coalescing
var displayName = name ?? "Guest";

// ??= - null-aware assignment
name ??= "Default";

// ! - null assertion
String notNull = name!;  // Throws nếu null

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📝 Chaining

var user = getUser();
var city = user?.address?.city ?? "Unknown";

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🔧 ?[]

var list = [1, 2, 3];
List<int>? nullableList;

print(list[0]);        // 1
print(nullableList?[0]);  // null

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✅ Checklist

• ?. safe access
• ?? default value
• ??= assign if null
• Avoid ! when possible

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