Getters In Dart

Getters in Dart provide a way to access the value of an object's property. They allow you to retrieve the value of a property in a controlled manner, enabling you to execute code before returning the value. This feature was introduced to Dart to provide a mechanism for accessing object properties while also allowing for additional logic or computations to be performed.

What are Getters in Dart?

In Dart, getters are special methods that provide read access to an object's properties. They are used to retrieve the value of a property in a controlled manner, allowing you to perform computations or apply logic before returning the value. Getters are defined using the get keyword followed by the getter name. When you access a getter, you invoke a method that computes the value to return.

History/Background

Getters have been a fundamental part of Dart since its inception as a language. They were introduced to provide a way to access object properties that require additional processing or validation before returning a value. By using getters, developers can encapsulate logic within the class and provide a clean interface for accessing properties.

Syntax

class MyClass {
  // private property
  int _value = 10;

  // getter method
  int get value {
    // additional logic can be added here
    return _value;
  }
}

void main() {
  var obj = MyClass();
  print(obj.value); // accessing the getter
}

In the above example:

• ✅ value is the getter method that retrieves the _value property.
• ✅ Inside the getter, you can add additional logic before returning the value.

Key Features

• ✅ Getters provide controlled access to object properties.
• ✅ They allow for encapsulation of logic within the class.
• ✅ Getters can be used to compute values dynamically.
• ✅ They enable the developer to maintain the object's state integrity.

Example 1: Basic Usage

Example
Copy
class Circle {
  double _radius;

  Circle(this._radius);

  double get area {
    return 3.14 * _radius * _radius;
  }
}

void main() {
  var myCircle = Circle(5);
  print('Area of the circle: ${myCircle.area}');
}
Try it Yourself

Output:

Area of the circle: 78.5

Example 2: Practical Application

class Temperature {
  double _celsius;

  Temperature(this._celsius);

  double get fahrenheit {
    return (_celsius * 9 / 5) + 32;
  }
}

void main() {
  var temp = Temperature(25);
  print('Temperature in Fahrenheit: ${temp.fahrenheit}');
}

Output:

Temperature in Fahrenheit: 77.0

Comparison Table

Common Mistakes to Avoid

1. Not Using Getters When Necessary

Problem: Beginners often forget to use getters when they want to compute a value based on other properties of a class. This can lead to unnecessary complexity and duplicated code.

// BAD - Don't do this
class Circle {
  double radius;

  Circle(this.radius);

  double area() {
    return 3.14 * radius * radius;
  }
}

Solution:

// GOOD - Do this instead
class Circle {
  double radius;

  Circle(this.radius);

  double get area => 3.14 * radius * radius;
}

Why: The first example uses a method to calculate the area, which can be more cumbersome to use. By using a getter, you can access area as if it were a property, making the code cleaner and more intuitive.

2. Overusing Getters

Problem: Some beginners tend to create getters for everything, even when a simple field would suffice. This makes the code unnecessarily complex.

// BAD - Don't do this
class Rectangle {
  double width;
  double height;

  Rectangle(this.width, this.height);

  double get getWidth => width; 
  double get getHeight => height;
}

Solution:

// GOOD - Do this instead
class Rectangle {
  double width;
  double height;

  Rectangle(this.width, this.height);

  double get area => width * height;
}

Why: In the first example, getWidth and getHeight are redundant since you can access width and height directly. Use getters only when they add value, such as computed values or when you want to encapsulate logic.

3. Forgetting to Mark Getters as `final`

Problem: Beginners may forget to declare getters as final, which can lead to confusion about their mutability.

// BAD - Don't do this
class Person {
  String name;

  Person(this.name);

  String get fullName {
    return name + ' Smith';
  }
}

Solution:

// GOOD - Do this instead
class Person {
  String name;

  Person(this.name);

  String get fullName => '$name Smith';
}

Why: In the first example, the fullName getter could be mistakenly thought to be mutable. By using a simple expression body with the => syntax, it clearly indicates that fullName is a computed property and not a method that changes state.

4. Not Understanding Getter Performance Implications

Problem: Some beginners may not realize that complex computations in getters can impact performance if they are accessed frequently.

// BAD - Don't do this
class Data {
  List<int> numbers;

  Data(this.numbers);

  int get sum {
    return numbers.reduce((a, b) => a + b); // Computationally expensive
  }
}

Solution:

// GOOD - Do this instead
class Data {
  List<int> numbers;
  int? _cachedSum;

  Data(this.numbers);

  int get sum {
    if (_cachedSum == null) {
      _cachedSum = numbers.reduce((a, b) => a + b);
    }
    return _cachedSum!;
  }
}

Why: In the first example, if sum is accessed multiple times, it will recompute the sum each time, which can be inefficient. Caching the result of expensive computations can improve performance, especially if the data doesn’t change often.

5. Confusing Getters with Setters

Problem: Beginners often confuse the purpose of getters and setters, mistakenly trying to use them interchangeably.

// BAD - Don't do this
class Temperature {
  double _celsius;

  Temperature(this._celsius);

  double get celsius => _celsius; // Getter
  void set celsius(double value) => _celsius = value; // Setter
}

Solution:

// GOOD - Do this instead
class Temperature {
  double _celsius;

  Temperature(this._celsius);

  double get celsius => _celsius;
  set celsius(double value) {
    _celsius = value;
  }
}

Why: The first example mistakenly implies that you can use the getter to set the value, which is not correct. Getters retrieve values, while setters are used to modify them. Understanding this distinction is crucial for proper class design.

Best Practices

1. Use Getters for Derived Properties

Using getters for properties that derive their values from other fields is a good practice. It helps encapsulate the logic and makes your API cleaner.

Why: This enhances readability and keeps the class flexible for future changes.

class Rectangle {
  double width, height;

  Rectangle(this.width, this.height);

  double get area => width * height;
}

2. Keep Getters Simple

Avoid putting complex logic in your getters. Instead, keep them straightforward and focused on returning values.

Why: Simple getters are easier to understand and maintain. They should ideally serve as a read-only view of your data.

3. Document Your Getters

Always document what your getters do, especially if they have any side effects or complex calculations.

Why: Good documentation helps other developers (or your future self) understand your code quickly.

4. Cache Expensive Computations

If your getter performs heavy computations, consider caching the result and returning the cached value on subsequent calls.

Why: This can significantly improve performance and reduce unnecessary calculations.

5. Use Consistent Naming Conventions

Follow consistent naming conventions for your getters. For instance, avoid prefixes like "get" in the getter names.

Why: Consistent naming increases code readability and makes it clear that a property is being accessed.

6. Test Your Getters

Write unit tests for your getters, especially if they contain any business logic or calculations.

Why: Testing ensures your getters behave as expected and helps you catch any errors early in the development process.

Key Points