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Godot Game Engine

Variant and Object

The Variant and Object classes are core concept of Godot's architecture and determine the way resources and scripts will be set up, so having a basic understanding of those classes is a good first step to get started with Godot. Don't be afraid if you find it all too abstract  you can always come back to it later once you have more experience in making games with the engine.

Variants

In the C++ code the Variant class (core/variant.h) is used to hold values of different types. Variants are used throughout the engine to carry values in different situations where it is necessary to hold values in a generic container. Example situations where Variants are used:

  • For any value that is carried in a GDScript variable or passed around,
  • For any value that is edited in the engine editor,
  • For any value that is serialized (for saving resources, transmitting over the network, etc.),
  • Values carried on keyframes of animations.
Variants carry all the basic types necessary for game development, i.e.:
  • Numbers (int, double, bool),
  • Strings (unicode),
  • Types to describe the space (Vector2, Vector3, Plane, Rectangle, AABB, Quaternion),
  • Matrices (Transform for 3D, Matrix32 for 2D),
  • Arrays (raw bytes, numbers, vectors, colors, Variants),
  • Dictionaries (using Variants for both keys and values),
  • Engine types (Object, RID),
  • Other misc types (Colors, Input Event, optimized scene paths).

Objects

Object is a basic type for most objects in the engine like scenes, nodes and resources that we will explain in the next chapter. Here we are still at a very abstract level, close to the engine conception.

As in most object-oriented programming language, the main features of the Object class are:

  • Inheritance. Objects know their type and inheritance line.
  • Reference. Object types are registered in the engine (ObjectTypeDB), and can be instanced using their type name. All instances of Object have a unique numerical ID, which can be used to reference the Object and retrieve the original instance if necessary (for example when working with a Foreign Function Interface to call other languages, such as Java).
  • Introspection. Objects describe their interfaces (properties and methods) using Variants. This description can be used to interact with the Object through various methods, for example:
    •   Serializing the Object,
    •   Calling the Object's methods and properties from GDScript (or any other scripting language),
    •   Animating the Object. An animation track can set values to the Object's properties, or call its methods,
    •   Editing. A generic editing UI can edit any property of the Object.

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