C++课件2chapter4-5

Chapter 4: data abstraction
Contents
Object-Oriented Programming(OOP); The syntax of C++; Class and Object; The important features of C++: e.g.. Function Overloading,Constants, inheritance,Polymorphism and virtual function;
class Clock { public: void SetTime(int NewH, int NewM, int NewS); void ShowTime（ ）; private: int Hour,Minute,Second; };
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Encapsulation
Definition: Combining the data member and code member abstracted from entity together as a whole Goal: Reinforce security and predigest（简化） programming. The user needn’t know the realization detail. Using the members of the class with special accessing (利用具有特殊访问类的成员 ) Purview by using the outer interface of the class（通过使用类的外部接口访问职
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Abstraction Example—Clock
Data abstraction：
int Hour, int Minute, int Second
Code abstraction：
SetTime( ), ShowTime( ).
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Abstraction Example—Clock
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Namespaces in headers
You’ll notice that using directives are present in nearly all the cpp files in this book, usually in the form: using namespace std; Since std is the namespace that surrounds the entire Standard C++ library, this particular using directive allows the names in the Standard C++ library to be used without qualification. In short: don’t put using directives（使用 指令）in header files.
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Object-oriented programming
Features:
Object : Data and data manipulation encapsulation;(封装是一种信息隐藏技术，即对象内部对用户是隐藏的，不可直接访问；用户只能见到对 象封装界面上的信息，通过对象的外部接口访问对象。封装的目的在于将对象的使用者和对象的设计者分开， 使用者无须知道对象内部实现的细节，只需要知道对象接收的消息即可。当用户向对象发送消息后，对象将根 据收到的消息来调用内部方法以做出响应。 Class: type; Interface : relation;(是用来描述关系用的，不能实现功能。接口只能做功能定义，但不能实现它。 Communication: message;(消息未必一定要通过函数传递，也可以通过公共的属性来传递消息。当然这要尽量 避免，不过编译器会放行不会做这种限制。)
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Object-oriented programming
Object
entity. Property method Object structure object name -attribute +Operation()
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Object-oriented programming
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Goals
To understand the concepts of object-oriented programming; To master the syntax of c++language programming; To master the principle & method of c++; To read, write, program and debug c++program
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Abstract data typing
Abstract is course of generalizing the actual object, getting the common characters of this object and describing the characters
General the actual object; Data abstract：attribute or state to the object Code abstract：To describe the mutual behavior character or function of a particular object Realization of abstract：using declaration of class
权范围内的消息） .
Realization of encapsulation： The “{ }” in the class
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Header file
In C++ the use of header files becomes crystal clear(非 常明显）. They are virtually mandatory (强制）for easy program development, and you put very specific information（特殊的） in them: declarations. The header file tells the compiler what is available in your library.
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The preprocessor directives
The preprocessor directive #define can be used to create compile-time flags. You have two choices: you can simply tell the preprocessor that the flag is defined, without specifying a value: #define FLAG you can give it a value (which is the typical C way to define a constant): #define PI 3.14159 In either case, the label can now be tested by the preprocessor to see if it has been defined:
一遍重复的定义同一个功能。如果没有变化的功能，继承就好。但 是现在对继承过度使用的情况也需要注意，能用“使用”能力达到 的就不要通过“继承”能力达到。 因为这样可以做松耦合而不是继承的紧耦合。对大型系统构造尤其重 要。 所谓多态，即一个名词可具有多种语义。 可以通过Function Overloading, virtual function实现，重载是指同一函数名以及运算符 可以具有不同含义的多种实现版本，编译器将根据函数调用的参数形 式决定调用哪一种实现版本。
dat a
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encapsulation
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Merit: Simple and independence(简单就是接口要尽可能简单明了，不要把不
相干的东西往里面塞，独立就是保持接口的独立性，不要彼此做不需要的关联。)
Reuse:inheritance and polymorphism(就是说你不需要一遍
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From C To C++
In order to compensate the insufficiency, Bjarne Stroustrup Bell Lab started to improve and to expand C, in 1980. At first it was called " C with class ", in 1983 named C++ officially, after 3 revision, has formulated ANSI C++ standard draft in 1994. Later time C++ still continuously development.
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The basic object
Step one is exactly that. C++ functions can be placed inside structs as “member functions.” struct Stash { int size; // Size of each space int quantity; // Number of storage spaces int next; // Next empty space unsigned char* storage; // Functions! void initialize(int size); void cleanup(); int add(const void* element); void* fetch(int index); int count(); void inflate(int increase); }; ///:~