Design Patterns: Flyweight Pattern
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Questions and Answers

What is the main problem that the Flyweight pattern solves?

  • Insufficient amount of RAM
  • Poor game performance on lower-end computers
  • Inefficient particle system
  • Redundant data storage in objects (correct)
  • Why did the game crash on the friend's computer?

  • The computer had less RAM than the developer's machine (correct)
  • The game was too complex for the computer
  • The particle system was too realistic
  • The game was not tested on lower-end computers
  • What was the distinctive feature of the game?

  • Realistic particle system (correct)
  • Realistic graphics
  • Realistic sound effects
  • Realistic physics engine
  • What fields in the Particle class consume the most memory?

    <p>Color and sprite</p> Signup and view all the answers

    What is the main difference between the color and sprite fields and the other fields in the Particle class?

    <p>The other fields are unique to each particle</p> Signup and view all the answers

    Why did the developer choose to implement a realistic particle system?

    <p>To make the game more realistic and immersive</p> Signup and view all the answers

    What was the consequence of not using the Flyweight pattern in the game?

    <p>The game crashed due to insufficient RAM</p> Signup and view all the answers

    What is the benefit of using the Flyweight pattern in the game?

    <p>Reduced memory usage and ability to fit more objects in RAM</p> Signup and view all the answers

    What represents the always changing context in which a particle exists?

    <p>Extrinsic state</p> Signup and view all the answers

    Which of the following is a characteristic of the intrinsic state?

    <p>It remains constant for each particle</p> Signup and view all the answers

    What is the main reason for applying the Flyweight pattern?

    <p>To reduce the memory consumption of objects</p> Signup and view all the answers

    What is the purpose of a separate context class in the Flyweight pattern?

    <p>To store the extrinsic state of a particle</p> Signup and view all the answers

    Why is immutability important in the Flyweight pattern?

    <p>To ensure that the flyweight object can be reused</p> Signup and view all the answers

    What is the purpose of a flyweight factory?

    <p>To provide convenient access to various flyweight objects</p> Signup and view all the answers

    Where can the factory method be placed in the Flyweight pattern?

    <p>In the flyweight class or a separate factory class</p> Signup and view all the answers

    What is the advantage of using a separate context class in the Flyweight pattern?

    <p>It allows for more elegant and efficient storage of extrinsic state</p> Signup and view all the answers

    What is the result of applying the Flyweight pattern in a game?

    <p>A thousand small contextual objects can reuse a single heavy flyweight object</p> Signup and view all the answers

    What is the relationship between the intrinsic state and the extrinsic state?

    <p>The intrinsic state and the extrinsic state are separate and distinct</p> Signup and view all the answers

    Study Notes

    Flyweight Design Pattern

    • A structural design pattern that lets you fit more objects into the available amount of RAM by sharing common parts of state between multiple objects.
    • Aimed at reducing memory consumption by minimizing duplicate data.

    Problem with Particle System

    • Each particle (bullet, missile, or shrapnel) was represented by a separate object containing plenty of data.
    • Newly created particles no longer fit into the remaining RAM, causing the program to crash.
    • Problem emerged due to insufficient amount of RAM on less powerful computers.

    Solution

    • Identify fields that consume a lot of memory (e.g., color and sprite) and store almost identical data across all particles.
    • Separate the object's state into intrinsic state (constant, unique to each particle) and extrinsic state (changing, unique to each particle).
    • Store the intrinsic state within the object (flyweight) and pass the extrinsic state to specific methods.

    Flyweight Pattern

    • Stop storing the extrinsic state inside the object.
    • Only the intrinsic state stays within the object, letting you reuse it in different contexts.
    • Result: fewer objects needed, since they only differ in the intrinsic state.

    Extrinsic State Storage

    • Move the extrinsic state to the container object (e.g., main Game object) or a separate context class.
    • Store coordinates, vectors, and speed of each individual particle, along with references to the flyweight object.
    • Use a single array in the container class or a separate context class for more elegance.

    Flyweight and Immutability

    • Ensure the flyweight object's state can't be modified.
    • Initialize the state via constructor parameters, and don't expose setters or public fields.

    Flyweight Factory

    • Create a factory method to manage a pool of existing flyweight objects.
    • The method accepts the intrinsic state of the desired flyweight, looks for an existing object, and returns it if found, or creates a new one.
    • Place the factory method in a flyweight container, a new factory class, or as a static method inside the flyweight class.

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    Description

    Understanding the Flyweight design pattern, which optimizes memory usage by sharing common state between multiple objects.

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