What is a virtual function?

Use of virtual functions

• yes C++ The mechanism used to implement polymorphism in ,“ Dynamic linking ”, The call of a class function is not determined at compile time , It is determined at the running time

class A
{
public:
virtual void foo0 {cout << "A::foo() is called"c<<endl;}
}
class B: public A
{
public:
virtual void foo0{ cout <<"B::foo0 is called" << endl;}
};
 that , In use , We can :
A *a = new B();// The parent class pointer points to the object of the child class 
a->foo();

• A constructor cannot be a virtual function
• The destructor of the base class should be a virtual function
• Friend function cannot be virtual , Because friend functions are not class members , Only class members can be virtual functions

Design patterns

• Practical application of object-oriented design principles , Encapsulation of classes , inheritance . encapsulation , Improve code reusability , Code readability and code reliability

Opening and closing principle

• Open to expansion , Turn off for changes , When demand changes , Without modifying the software entity , It can extend the function of the module , To meet new needs ;
• Software testing focuses on testing the extended new code ;
• Improve the maintainability of the software , Stronger maintainability and continuity ;
• “ Abstract constraints , Packaging changes ”

Richter's principle of substitution

• Inheritance must ensure that the properties owned by the superclass still hold in the subclass

The principle of Dependence Inversion

High level modules should not rely on low-level modules , Both should depend on abstraction ;

CIass JDshop : public Shop{
	virtuall void sell0;
)
Class Customer{
	void shopping(Shop *pShop)
{
	cout<<Customer.name<< pShop-sell0<<endl:
}

Principle of single responsibility

Interface isolation principle

Dimitar's law

Synthetic multiplexing principle

Design patterns, behavioral

• It is used to describe the complex process control of a program at run time , That is, it describes the cooperation between multiple classes or objects to jointly complete tasks that cannot be completed by a single object .

Template pattern

• Step execution sequence of known algorithm , But the specific implementation of some steps is unknown ;
• Define the algorithm skeleton of an operation , And delay some steps of the algorithm to subclasses , So that the subclass can redefine some specific steps of the algorithm without changing the structure of the algorithm ;

class Frame
{
public:
	 
};