Custom Getters and Setters

Custom Getters and Setters

About

• Explicit Control: Custom access logic
• Validation: Check values before setting
• Computation: Derived properties
• Syntax: Maintains field-like access

Main Topics

1. Basic Syntax

   • Definition: get/set keywords

   • Example:

     class Temperature {
       double _celsius;
     
       double get fahrenheit => _celsius * 9/5 + 32;
       set fahrenheit(double f) => _celsius = (f - 32) * 5/9;
     }

2. Validation

   • Definition: Check input values
   • Example:

     set age(int value) {
       if (value < 0) throw ArgumentError();
       _age = value;
     }

3. Derived Properties

   • Definition: Computed on access
   • Example:

     get fullName => '$firstName $lastName';

4. Read-only

   • Definition: Getter without setter
   • Example:

     get area => length * width;

5. Logging

   • Definition: Track access
   • Example:

     set value(int v) {
       print('Value changed to $v');
       _value = v;
     }

How to Use

• Validation: Protect invariants
• Derived Data: Compute when needed
• Debugging: Add access logging
• Compatibility: Maintain API while changing implementation

How It Works

1. Invocation: Called on access
2. Syntax: Looks like field access
3. Performance: Small overhead
4. Optimization: JIT may inline

Example:

class BankAccount {
  double _balance = 0;

  double get balance => _balance;

  set deposit(double amount) {
    if (amount <= 0) throw ArgumentError();
    _balance += amount;
  }

  set withdraw(double amount) {
    if (amount > _balance) throw StateError();
    _balance -= amount;
  }
}

Conclusion

Custom getters and setters enable precise control over property access, allowing for validation, computed values, and other logic while maintaining clean field-like syntax. They’re essential for maintaining class invariants and creating robust APIs.