Object Oriented Programming
- Objects send and receive messages(objects do things!)
Objects send messages
- Messages are
-Composed by the sender
-Interpreted by the receiver//kouyi
-Implemented by methods//shishi
- Messages
- May cause receiver to change state
- May return results
Object vs. Class
Object (cat)
Represent things,events, or concepts
Respond to messages at run-time
Classes(cat class)
Define properties of instances
Act like types in C++
OOP Characteristics
1.Everything is an object.
2.A program is a bunch of objects telling each other what to do by sending messages.
3.Each object has its own memory made up of other objects.
4.Every object has a type.
5.All objects of a particular type can receive the same messages.//正反理解
An object has an interface
The interface is the way it receives messages.
It is defined in the class the object belong to.
Functions of the interface
- Communication
- Protection
The Hidden Implementation
- Inner part of an object,data menbers to present its state,and the actions it takes when messages is rcvd id hidden.
- Class creators vs. Client programmers
-Keep client programmers‘ hands off portions they shoule not touch.
-Allow the class creators to change the internal working of the class without worrying about how it will affect the client programmers.
Encapsulation//封装
- Bundle data and methods dealing with these data together in an object
- Hide the details if the data and the action
- Restrict only access to the publicized methods.