In object-oriented programming: Are attributes and states really equivalent?

Object-oriented programming: a detailed interpretation of properties and states

In object-oriented programming, properties and states are often confused, and the two are closely related but different. This article will deeply explore the role and differences between attributes and states in objects, and answer the core question of "whether attributes and states are equal."

In the article, Teacher object is used as an example and status attribute is used to represent its status (teaching, eating, sleeping). The value of status will change according to the call of methods such as teach , eat , sleep , etc., which seems to indicate that the status can be represented by attributes.

However, not all properties represent the state of the object. It depends on our understanding of "state". status attribute reflects the dynamic behavior of Teacher object and is a typical manifestation of state. But if other attributes are considered, such as the teacher's date of birth or the radius of the circle, these attribute values ​​are usually unchanged throughout the life of the object. These static properties are not the state of the object, but the descriptive information of the object.

Therefore, attributes are means to describe the characteristics of an object, and states are the dynamic representation of an object at a specific moment. Attributes can be used to represent states, but not all attributes represent states. The attributes can be static descriptive or dynamic, and are used to reflect the state of the object. The key is whether the attribute value changes due to object behavior or time. If the property value changes, it is likely to represent the state of the object; otherwise, it may be just an inherent property of the object.

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