Alice Teaches OOP: Expanded Glossary of Key Terms
When learning Object-Oriented Programming (OOP) with Alice, understanding the terminology is essential. Here is an expanded glossary to help clarify the concepts used within the Alice programming environment, supported by references to online resources.
World
In Alice, a “world” is a container for all objects, methods, and interactions. The world is saved as an .a2w file and acts as the overarching environment where all objects and actions exist. Much like a real-world space, everything in Alice takes place inside this world.
- Source: Alice.org
Object
Objects are three-dimensional entities such as people, animals, or furniture in your world. They can also include two-dimensional items like text and billboards. Objects are added to the world using the “Add Objects” button, though some essential objects (e.g., ground, camera, lights) are preloaded.
Properties
Every object in Alice has properties that define its attributes, such as color, visibility, and position.
- Color: The available colors in Alice are limited to a set of predefined options such as red, green, blue, yellow, and black. To make an object white, users must select “no color.”
- Opacity: A property that controls how transparent an object is, ranging from 0% (invisible) to 100% (fully opaque). It allows for smoother transitions when combined with animation.
- isShowing: This Boolean property determines whether or not an object is visible. This property provides an instantaneous change in visibility.
- Vehicle: A one-way relationship where one object “rides” along with another. For example, if a character rides in a car, setting the car as the character’s vehicle ensures that the character moves with the car.
- Skin Texture: Users can wrap a two-dimensional image around objects, such as applying a grass texture to the ground.
- Source: Alice Community Wiki
Class
A class is the template or blueprint from which objects are instantiated. All objects of a certain class (e.g., “Chicken”) share the same attributes and methods. When you place an object in your world, you are essentially creating an instance of that class.
Method
Methods are predefined or custom-built actions associated with an object. For example, all objects can “move,” “turn,” or “say” something, but you can also write more complex methods by combining simpler ones. Custom methods in Alice allow users to create reusable blocks of actions that can be applied to different objects.
- Source: Alice.org
Parameters
Methods can accept parameters, which are additional pieces of information that guide the action. For instance, the “move” method requires a parameter specifying how far the object should move.
Variables
Variables in Alice store values that can change during the execution of your world. Variables can be world-level, class-level, or method-level, each with different scopes.
- World-Level Variables: Accessible throughout the entire world and all methods.
- Class-Level Variables: Linked to a specific object and can be shared among methods within that object.
- Method-Level Variables: Only used within a single method, making them temporary and limited in scope.
- Source: Alice Wiki – Variables
Events
Events trigger methods. Without events, objects remain idle, no matter how well-defined the methods are.
- When The World Starts: Triggers an action when the world begins.
- When A Key Is Typed: Triggers a method when a specific key is pressed.
- While Something Is True: Continuously triggers a method while a condition is true.
- Source: Alice.org – Events
Functions
Functions in Alice return values based on calculations or data from the world. For example, functions can compute distances between objects or retrieve specific object properties like orientation or size. Unlike properties, functions usually calculate a result.
- Source: Alice Project
Lists and Arrays
Lists and arrays are ways to store collections of items in Alice:
- Lists: A flexible collection of objects where order is not strictly maintained.
- Arrays: A more structured collection where items are indexed, allowing for direct access to individual elements.
- Source: Alice Programming Concepts
Tags in the Method Editor
At the bottom of the method editor, you’ll find colored tags that help organize code execution. These include:
- Do In Order: Executes actions sequentially.
- Do Together: Executes actions simultaneously.
- If/Else: Executes code based on whether a condition is true or false.
- Loop: Repeats code for a set number of iterations.
- While: Repeats code while a condition is true.
- Source: Alice.org Method Editor
Poses
Poses save specific positions or stances of an object. This is especially useful for animations where you want to toggle between different positions (e.g., dance moves).
- Source: Alice.org Poses
Comments
Comments are lines of text added to the code to explain certain sections for the benefit of the programmer. These lines do not execute and are used solely as notes.
- Source: Alice.org – Comments
Conclusion
Understanding the terms and concepts in Alice is crucial to mastering Object-Oriented Programming in a visually interactive environment. Whether you’re controlling an object, adjusting properties, or writing custom methods, knowing these terms ensures smooth programming. For more detailed guidance and tutorials, visit the official Alice website or explore additional learning resources online.
