Golang - Memento Pattern

Golang - Memento Pattern

Games often require some kind of save and load system to allow the player to resume their progress from where they left off. The "Memento Pattern" is a perfect fit for this kind of system. In this article, we will discuss how to use the "Memento Pattern" in Golang to implement a load and save system for games.

Components of the Load and Save System

The "Memento Pattern" consists of three components: Originator, Memento, and Caretaker. In the context of the load and save system, we can define them as follows:

  • Originator: This is the object whose state needs to be saved and restored. In the case of a game, it could be the player's character, the game world or any other object that needs to be saved and restored.

  • Memento: This represents the saved state of the Originator. In the case of a game, it could be a file that contains the player's progress or the state of the game world.

  • Caretaker: This is responsible for storing and retrieving the Memento. In the case of a game, it could be a save file manager that stores and retrieves the player's progress or the state of the game world.

Implementation

Let's implement the load and save system for a game using the "Memento Pattern" in Golang.

Originator

First, let's create an Originator interface that defines the methods required to save and restore the state of the game object.

type Originator interface {
    Save() Memento
    Restore(Memento)
}

We can then create a struct that implements this interface. In this example, we will create a struct called "GameWorld" that represents the state of the game world.

type GameWorld struct {
    level int
    score int
}

func (g *GameWorld) Save() Memento {
    return Memento{level: g.level, score: g.score}
}

func (g *GameWorld) Restore(m Memento) {
    g.level = m.level
    g.score = m.score
}

Memento

Next, we can create a struct that represents the Memento. In this example, we will create a struct called "Memento" that stores the level and score of the game world.

type Memento struct {
    level int
    score int
}

Caretaker

Finally, we can create a Caretaker that will store and retrieve the Memento. In this example, we will create a struct called "SaveFileManager" that contains a list of Mementos.

type SaveFileManager struct {
    mementos []Memento
}

func (s *SaveFileManager) Save(m Memento) {
    s.mementos = append(s.mementos, m)
}

func (s *SaveFileManager) Load(index int) Memento {
    return s.mementos[index]
}

Usage

Now that we have implemented the Load and Save system using the "Memento Pattern", let's see how we can use it in our game.

func main() {
    gameWorld := &GameWorld{level: 1, score: 0}
    saveFileManager := &SaveFileManager{}

    // Save the initial state of the game
    saveFileManager.Save(gameWorld.Save())

    // Increase the level and score
    gameWorld.level++
    gameWorld.score += 1000

    // Save the new state of the game
    saveFileManager.Save(gameWorld.Save())

    // Restore the previous state of the game
    gameWorld.Restore(saveFileManager.Load(0))

    fmt.Println(gameWorld)
}

In this example, we first create a GameWorld object with an initial level and score. We then create a SaveFileManager object.

We save the initial state of the game using the Save() method of the GameWorld object and add it to the SaveFileManager. We then increase the level and score of the game and save the new state of the game.

Finally, we restore the previous state of the game using the Load() method of the SaveFileManager and the Restore() method of the GameWorld object.

Conclusion

The "Memento Pattern" is a powerful pattern that can be used to implement a load and save system for games. In this article, we discussed how to use the "Memento Pattern" in Golang to implement a load and save system for games. We saw how to define the Originator, Memento, and Caretaker components and how to use them in our game.


References

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