Builder Class in Dart Programming Language

Introduction to Builder Class in Dart Programming Language

The Builder pattern is a creational design pattern that can be used during the design of software, especially when developing objects using object-oriented programming. It addresses c

onstructing complex objects in a step-by-step manner. Dart, which incidentally is an object-oriented and class-based language, makes use of design patterns like the Builder to simplify object creation. We will continue, in this article, examining the Builder class in Dart, describing its purpose, its benefits, and giving practical examples to help you acquire this concept.

What is the Builder Pattern?

The Builder Pattern is one of the creational design patterns commonly used in object-oriented programming. Its main goal is to help construct complex objects step by step, without requiring the object creation process to become complicated or tightly coupled to a constructor with many parameters.

Key Concepts of the Builder Pattern:

1. Separation of Construction and Representation: The Builder design pattern separates the object reconstruction process from how an object is represented or configured. This makes it possible to implement much more flexible objects than if all the attributes were passed right into a constructor. The Builder class assumes the responsibility of object construction piece by piece.
2. Steps of Construction Are Independent: Construction steps can be multiple, and each can be executed independently. For example, when building a complex object comprising several fields or configurations (like a pizza order or GUI), the builder allows you to add or amend components in steps, similar to how one would add toppings on pizzas or on elements of a GUI. In this case, the object is only fully realized when all that needs to be done for it is complete.
3. Same Construction Process for Different Representations: One of the powerful aspects of the Builder Pattern is that it affords one and the same construction process to produce a family of different “representations” of an object. For example, using a builder class you can construct the same product (say a house) but with different attributes such as the material type, number of rooms, style, etc. Having the same series of method calls but with different configurations in the builder, one can end up with different final objects.

Builder Class Structure in Dart Language

A builder in Dart typically involves two main components:

• The Builder Class, which has methods for configuring and constructing the object.
• The Product Class, which is the final object created by the builder.

Here’s a basic structure:

class Product {
  final String name;
  final int quantity;
  final double price;
  
  Product._(this.name, this.quantity, this.price);
}

class ProductBuilder {
  String? _name;
  int? _quantity;
  double? _price;

  // Setters for each field
  ProductBuilder setName(String name) {
    _name = name;
    return this;
  }

  ProductBuilder setQuantity(int quantity) {
    _quantity = quantity;
    return this;
  }

  ProductBuilder setPrice(double price) {
    _price = price;
    return this;
  }

  // Method to build the final product
  Product build() {
    return Product._(_name ?? 'Unknown', _quantity ?? 0, _price ?? 0.0);
  }
}

Example: Building a Product

Let’s see how the ProductBuilder class can be used to create an instance of the Product class:

void main() {
  Product product = ProductBuilder()
    .setName('Laptop')
    .setQuantity(5)
    .setPrice(999.99)
    .build();

  print('Product: ${product.name}, Quantity: ${product.quantity}, Price: \$${product.price}');
}

Output:

Product: Laptop, Quantity: 5, Price: $999.99

In this example, the ProductBuilder allows for the step-by-step construction of the Product object. You can also see how methods like setName(), setQuantity(), and setPrice() provide flexibility in configuring the object.

• Private Constructor in Product Class: The constructor of the Product class is private (Product._). This ensures that the object cannot be instantiated directly but only through the builder class.
• Chained Methods: The builder class uses method chaining. Each setter method in ProductBuilder returns this, enabling you to chain the method calls together in a readable manner.
• Default Values: Each field in the ProductBuilder is optional, and if not set explicitly, the builder provides default values (e.g., "Unknown", 0, or 0.0).
• Separation of Concerns: The ProductBuilder class focuses solely on configuring and constructing the Product object. This separation of concerns keeps your code modular and easier to maintain.

Real-World Use Case: Building a Pizza Order

real-world example where the Builder pattern is useful—building a pizza order with various customizable options like crust type, size, and toppings.

class Pizza {
  final String crust;
  final String size;
  final List<String> toppings;
  
  Pizza._(this.crust, this.size, this.toppings);
}

class PizzaBuilder {
  String _crust = 'Thin Crust';
  String _size = 'Medium';
  List<String> _toppings = [];

  PizzaBuilder setCrust(String crust) {
    _crust = crust;
    return this;
  }

  PizzaBuilder setSize(String size) {
    _size = size;
    return this;
  }

  PizzaBuilder addTopping(String topping) {
    _toppings.add(topping);
    return this;
  }

  Pizza build() {
    return Pizza._(_crust, _size, _toppings);
  }
}

void main() {
  Pizza pizza = PizzaBuilder()
    .setCrust('Thick Crust')
    .setSize('Large')
    .addTopping('Pepperoni')
    .addTopping('Mushrooms')
    .build();

  print('Pizza Order: ${pizza.size} pizza with ${pizza.crust} and toppings: ${pizza.toppings.join(', ')}');
}

Output:

Pizza Order: Large pizza with Thick Crust and toppings: Pepperoni, Mushrooms

In this example, the PizzaBuilder allows for the creation of a customizable pizza order, where various options like crust type, size, and toppings can be set.

Pros and Cons of Using the Builder Pattern in Dart

Advantages of Builder Class in Dart Programming Language

The Builder Class in Dart, as well as generally in programming, follows the Builder Pattern. It is a design pattern primarily used to construct complex objects. The pattern offers several key advantages, improving code readability, maintainability, and flexibility. Let’s look a little closer at the benefits of the Builder Class in Dart programming:

1. Improves Readability and Maintainability

• In the Builder pattern, each part of object construction is both named and separated into methods. Instead of having a very complex constructor, when you construct a Pizza object, you might have methods like setCrust(), setSize(), addToppings(), etc. This will make your code more readable as your objects have a lot of attributes.
• It makes maintenance easier since the process of creating an object is decoupled from an unwieldy constructor.

Example:

Pizza pizza = PizzaBuilder()
  .setCrust('Thick Crust')
  .setSize('Large')
  .addTopping('Mushrooms')
  .build();

This is far more readable than passing in a host of parameters into a constructor.

2. Manage Complex Objects with Multiple Fields

• Builder Class manages the creation of complex objects having multiple fields along with their configuration. Instead of constructor overloading with an immense number of parameters, the construction process can be broken down into smaller methods.
• This is especially useful when working with objects that have some required fields and some optional. The Builder Class makes the creation of objects easier without needing to create a number of overloaded constructors.

Example: A Car object might have several optional features, including sunroof, GPS, and automatic window functionality; the builder allows you to configure only the options you actually want.

3. Supports Method Chaining

• One of the most useful features that the Builder Class proposes is method chaining, meaning that more than one method call can be combined in one statement. It proposes conciseness, which maintains readability while being efficient.
• The builder returns this after every method call, which enables chaining and makes the final code much more compact without sacrificing readability.

Example:

Pizza pizza = PizzaBuilder()
  .setCrust('Thin Crust')
  .setSize('Medium')
  .addTopping('Olives')
  .addTopping('Cheese')
  .build();

This is far better than having a constructor take an enormous amount of arguments.

4. Reduces the Chance of Error

• The Builder Pattern ensures that only completely initialized objects are instantiated, thus reducing the chance of incomplete or poorly configured objects. For example, it can assure that required fields are set before the build() method is invoked.
• In cases where the class contains many optional fields, the builder allows you to instantiate an object without concern for missing parameters or default values.

5. Allows for Flexibility in Object Creation

• The Builder Pattern allows for flexibility on how an object is created so that different configurations may be achieved without having to change the implementing class. You are able to create different types of an object by invoking various combinations of the builder methods.
• This flexibility is of great use when one has to deal with the creation of variants for an object, say a Pizza with various toppings or a Car with various features.

Example: Using the same PizzaBuilder, you could get either VeganPizza or MeatLoverPizza depending on what toppings it uses.

6. Immutability

• This often happens with the Builder Pattern: the resulting objects are immutable, meaning that after having them constructed, their state cannot be changed anymore. This is a good practice because, in general, it boosts program stability and reduces bugs that can arise from unforeseen changes to an object after it has been created.
• You want to use this approach when it’s necessary to ensure that data integrity persists for the lifetime of the application.

Example:

class Pizza {
  final String crust;
  final String size;
  final List<String> toppings;
  
  Pizza._(this.crust, this.size, this.toppings);
}

Here, the Pizza class is immutable, and its fields cannot be modified after the object is built.

7. Facilitates Unit Testing

• Since the Builder Pattern separates the construction logic into individual methods, it becomes easier to test each step of the construction process in isolation. You can write unit tests to ensure each method in the Builder class (like setSize(), addTopping()) behaves correctly, without needing to test the entire object creation logic at once.
• This modular approach simplifies both testing and debugging when building complex objects.

8. Provides Default Values

• The builder allows for setting default values for fields. This is useful for objects where certain attributes have common default values, but can still be customized by the user when needed.
• You don’t have to pass in every value when building the object; you only need to modify the values you care about, while default values handle the rest.

Example:

class PizzaBuilder {
  String _crust = 'Thin Crust';  // Default value
  String _size = 'Medium';       // Default value
  List<String> _toppings = [];
}

In this case, the pizza has default values for the crust and size unless the user explicitly changes them.

9. Encapsulates Construction Logic

• The Builder Pattern encapsulates the object construction logic within the builder, preventing the main class from becoming cluttered with the details of how its instances are created. This separation keeps the main class focused on its behavior, making the codebase more modular and maintainable.
• It also helps avoid scenarios where the main class has a constructor overloaded with too many parameters.

10. Ensures Consistency and Completeness

• The Builder Pattern enforces consistency in the object creation process by requiring that all required fields are set before the object is built. The final build() method typically validates the input, ensuring that the object is fully constructed with all the necessary fields.
• This reduces the likelihood of encountering incomplete or inconsistent objects.

Disadvantages of Builder Class in Dart Programming Language

While the Builder Class is a host of benefits to programming Dart, there are noted disadvantages that are associated with the use of the Builder Class. These are basically issues related to complexity it introduces, performance issues it might introduce, and certain limitations that might be seen in the application of the class. Let us see some disadvantages of Builder Class in programming using Dart:

1. Increased Complexity for Simple Object Construction

• The Builder Pattern is most useful when one needs to create complex objects with many fields. For simple ones, which take only a few parameters in their constructors, the usage of a Builder introduces redundancy.
• In other words, it is overkill using a Builder class when a simple constructor would do the job, resulting in more complicated code for relative simple tasks.

Example:

class Car {
  String model;
  Car(this.model);
}

Here, a simple constructor is more than enough. Introducing a Builder for such cases would add unnecessary complexity.

2. More Code and Boilerplate

• It also requires more code when using the Builder Pattern, since you need to create extra classes or methods that assist in object construction. Say, you would have to create a dedicated Builder class and a setter method for every field. This would increase boilerplate code.
• This often inflates codebases, especially for projects relying heavily on Builders for a large number of classes. Besides that, it is pretty impractical to write and then maintain extra code for the Builder class in the long term.

Example:

class CarBuilder {
  String? _model;
  CarBuilder setModel(String model) {
    _model = model;
    return this;
  }
  Car build() {
    return Car(_model!);
  }
}

3. Performance Overhead

• One minor performance overhead can be considered with the Builder Pattern, mainly because of the additional steps in constructing an object. Instead of having an object initialized directly through a constructor, it requires method calls to set each property, and with an additional call to build() to finalize it.
• This creation of objects in such applications should be recurrent and fast, which involves game development and real-time systems. The additional overhead could be harmful in those environments.

4. Potential Memory Consumption

• Possible Memory Use Because the Builder Class often uses intermediate objects while building-this can take the form of storing several states before the final object will be created-it is likely to use more memory in comparison to the traditional constructor-based approach.
• This can be a weakness for memory-constrained environments where efficient memory management is crucial.

5. Reduced Intuitiveness for Simple Cases

• Developers without experience with the Builder Pattern may find that its utilization is counter-intuitive in cases where there is no complex creation logic for an object. If obviously a simple way exists to do this via a constructor, applying the Builder Pattern may seem over-engineered and abstract.
• This easily can lead to confusion for teams or developers unacquainted with the pattern, overcomplicating simple development tasks.

6. Less Direct Initialization

• With the Builder Pattern, objects are not initialized in one go but are built step by step through successive method invocations, which may be less intuitive than using constructors when all the fields are initialized directly.
• This multistage initialization can become even more indirect, and even cumbersome to read, when builders are being used in a very high-frequency manner in an application.

Example:

Car car = CarBuilder()
  .setModel("Sedan")
  .build();

Compared to:

Car car = Car("Sedan");

7. Increased File Size

• For large projects, using Builders extensively can increase the file size because each Builder requires its own class, along with methods for every possible attribute. This makes the codebase larger, which can affect both readability and maintainability.
• Overuse of the Builder Pattern may lead to bloated classes, and managing these files can become challenging, especially when the project scales.

8. Can Lead to Overengineering

• While the Builder Pattern is highly beneficial for complex objects, there’s a risk of overengineering when applied to simple use cases. Introducing Builders for every object in the codebase, even those that don’t require it, can result in unnecessary abstraction and complexity.
• This can lead to a situation where the pattern is misused, and code that could have been straightforward is made more complex for no real benefit.

9. Limited Use in Immutable Object Creation

• Although the Builder Pattern supports immutability by constructing fully initialized objects, it may not always align perfectly with Dart’s const keyword, which is used for compile-time constant objects.
• Builders generally don’t handle const objects since they rely on runtime initialization, so if your project requires a lot of immutable objects that need to be const, the Builder Pattern may not be suitable.

Example:

const Car car = Car("Sedan");  // Impossible with Builder Pattern

10. Less IDE Support for Builder Pattern in Some Cases

• Modern IDEs, such as VS Code or IntelliJ, mitigate a lot of this pain through autocompletion among other features. These work less seamlessly when you are using a Builder Pattern.
• For instance, in the case of Constructors, as soon as it is necessary to create an object, the parameter suggestions pop up right away, whereas Builders usually use method chaining and might not support the autocompletion of all the attributes during the building process.