Question

What is the difference between the state and the behaviour of a class?

Short answer

State refers to attributes; behaviour refers to methods.

Step-by-step solution

Define Class State

The state of a class refers to the data or attributes that are associated with a class. These attributes hold the information about the object created from the class. For instance, in a 'Car' class, the state might include attributes such as 'color', 'model', and 'speed'.

Define Class Behaviour

The behaviour of a class refers to the methods or functions that define the actions or operations that a class can perform. Using the 'Car' class example again, behaviours might include methods such as 'accelerate()', 'brake()', and 'turn()'. These methods manipulate the state of the object.

Compare State and Behaviour

State and behaviour are complementary aspects of a class. The state is represented by the variables (attributes), whereas the behaviour is determined by the functions or methods. For every change in behaviour, state might be affected, showcasing their interconnected nature.

Key concepts

class state

Every class in object-oriented programming holds a set of attributes. These attributes are distinct pieces of information that describe the object. Think of the attributes as a collection of facts about the object. They create what is known as the "state" of the class.
For example, if you had a class titled `Car`, the state could be formed by attributes like `color`, `model`, and `speed`. These are the characteristics that define a particular instance of a car. The state of a class is important because it tells us the current values of these attributes at any given time.
When you modify an attribute such as increasing the `speed`, you are altering the state of that class instance. Thus, the state serves as an indicator of the object's current condition and directly influences its behavior.

class behaviour

In object-oriented programming, the behavior of a class is defined by its methods. These methods act as a set of instructions or actions that can be performed on the class's state.
For our `Car` class, possible behaviors could include actions like `accelerate()`, `brake()`, and `turn()`. Each of these methods will have a direct impact on the car's state. For instance, invoking the `accelerate()` method might increase the `speed` attribute, altering the existing state.
The methods are like verbs, describing what the object can do. They help in interacting with and manipulating the state. It is crucial to understand that behaviors are responsible for making the class dynamic. Without behaviors, your class would merely be a static collection of data.

attributes and methods

Classes in object-oriented programming are like templates. They allow us to create objects that share common structure and function.
Attributes and methods are the two core components that make up a class. Attributes, as described, are the pieces of data stored within an object, forming its state. Methods, on the other hand, represent the behavior, providing ways to interact with or modify the state.
Using our `Car` class again, `color`, `model`, and `speed` are attributes, while actions like `accelerate()` and `brake()` are methods. Together, they give the class a complete structure. This structure allows objects to not only hold data but also to perform tasks. Understanding how attributes and methods work together is essential for maximizing the potential of object-oriented programming. With logical and meaningful methods operating on relevant attributes, a class can effectively model complex real-world entities.