* No parentheses are allowed when creating an object with a no-argument constructor
Circle circle1 (); is wrong
CIrcle circle1 ; is correct
* Avoid multiple includes
If the header file of a class is defined multiple times in head files or source files , the following methods can be used:
#ifndef CIRCLE_H
#define CIRCLE_H
{
}
#endif
* Inline functions improve function execution efficiency (for short functions)
inline int number;
Or write the function definition directly in the class class
*get and set functions are to ensure data field encapsulation
The Get function is an accessor:
double getRadius();
When the return type is bool : Naming convention: bool isPropertyName ();
The Set function is a mutator
void setRadius(double);
* Variables can be initialized at declaration time, but a class member cannot be initialized at declaration time
*string s("welcome to c++); Equivalent to string s = "welcome to c++"; Equivalent to char s1[] = "welcome to c++";//The former is more efficient
*string s;// Create an empty string
* When the parameter is an object, it is actually passed by value, and the content of the object is copied to the parameter of the function
Pass-by-reference actually means: the parameter of the function is an alias of the object, it is better to use pass-by-reference
The *static keyword means that no matter which object of the class can be called, and all call the same member
Creating a circle1 object increments NumberOfObject by one, and creating a circle2 object increments NumberOfObject by one
Static variables and static functions can be accessed without creating an object
// You should use ClassName::functionName(arguments) to call static functions, and use ClassName::staticVariable to access static variables, which can improve program readability
When to declare static: variables and functions should be declared static if they do not depend on any class object
*const keyword: means read-only member function,
Syntax: put the const keyword at the end of the function header: int getNumber()const;
When defining, add constA after the function header