In the world of game development, understanding the concept of objects is akin to understanding the DNA of a game. Objects are the building blocks, the fundamental units that give life to your game. They are the characters, the enemies, the power-ups, the bullets, the walls, and even the invisible controllers that orchestrate the game’s flow. In GameMaker Language (GML), the concept of objects takes center stage, and understanding them is paramount to creating any game. This article will delve into the essence of objects in GML, explaining them in a simple, relatable manner with analogies and code examples.
The Concept of Objects in GML
Imagine you’re a chef, and you’re about to prepare a meal. You have a recipe in front of you, which is a set of instructions on how to prepare the meal. In GML, an object is like that recipe. It’s a blueprint or a template that defines how a particular element in the game should behave. It contains a set of instructions (events and actions) that dictate what happens under specific circumstances.
Now, when you follow the recipe and prepare the meal, that meal is an instance of the recipe. Similarly, in GML, when an object is placed in a room (the game’s playing field), it becomes an instance of that object. Each instance is a unique manifestation of the object, capable of having its own properties and behaviors.
The Birth of an Object
Creating an object in GML is like writing a recipe. You define what ingredients you need (variables), what steps to follow (events), and what to do in each step (actions or code). To create a new object, you simply right-click on the Objects asset folder and select Create. This opens the Object Editor window, where you can name the object and assign it a sprite (a graphical representation).
Here’s a simple example of creating an object in GML:
// Create a new object
obj_player = instance_create(0, 0, obj_player);
// Assign a sprite to the object
obj_player.sprite_index = spr_player;
In this example, we create a new object obj_player and assign it a sprite spr_player.
The Life of an Object
Once an object is created, it can be placed in a room, where it becomes an instance. Each instance of an object has its own life cycle, which is governed by events. Events are specific moments or triggers in the game loop, such as the creation of an instance, a step in the game, a collision with another instance, a mouse click, and so on.
When an event is triggered, the instance follows the instructions (actions or code) defined in the object for that event. For example, if an instance of a player object collides with an instance of an enemy object, the player might lose health, or the enemy might be destroyed.
Here’s an example of defining a collision event in an object:
// In the player object, define a collision event with the enemy object
if (place_meeting(x, y, obj_enemy)) {
// Reduce the player's health
health -= 1;
}
In this example, when an instance of the player object collides with an instance of the enemy object, the player’s health is reduced by 1.
The Death of an Object
Just as an object can be created, it can also be destroyed. When an instance is destroyed, it triggers a Destroy Event, which is the last event to be executed for that instance. This event is useful for creating effects when an instance is destroyed, such as an explosion, or for updating the game state, such as increasing the score.
Here’s an example of using the Destroy Event:
// In the enemy object, define a Destroy Event
instance_destroy();
// Increase the score
score += 100;
In this example, when an instance of the enemy object is destroyed, the score is increased by 100.
The Power of Objects
Objects in GML are powerful and flexible. They can have a sprite associated with them, which allows them to be visible in the game, but they can also be invisible, acting as controllers that manage the game’s flow. They can interact with each other, respond to user input, and even change their own properties and behaviors during the game.
Understanding objects in GML is like understanding the secret language of your game. It allows you to create complex, interactive, and dynamic games, where every character, every enemy, every item, and every event is an instance of an object, following the blueprint that you’ve defined.
In the next part of this series, we’ll delve deeper into the power of objects in GML, exploring how to use them to create complex behaviors, interactive gameplay, and dynamic game worlds. Stay tuned!
