Class ?. XML

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Class

???? All classes ?? There is only one destructor and a value assignment function ???????????? But there can be multiple constructors ??? For any class, the C ++ compiler automatically generates four default functions :??????? A ()?? //? The default no-argument constructor ??? If any constructor is defined, the default constructor is invalid ??????? A (const? A? & );? //? The default copy constructor is the shortest copy ?????? A &? Operator = (const? A? & )?;? //? Default Value assignment function ?????~ A (); default destructor ??

By type

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1? Default constructor

?? A ();????????? The default constructor generated by the compiler?

2? Copy constructor

??? If there is only one constructor parameter and the parameter type is set to this type, the constructor is copied .?? For example, a (A &) A (const? A &) a (A &, Int? I = 0 )??? // If other parameters have default values, is this constructor also a copy constructor?

2.1? Default copy constructor

?? A (const? A? & );??? Shallow copy ?? Normal copy ?? Which of the following is a simple one-to-one assignment of new objects with the data of?

2.2? Deep copy

? A (const? A & )?;?? Dynamic space allocation?

When will the copy function be called?

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1 )????????? Initialize with another object

A??a;A??b=a;A??c(a);?

2) value transfer

???Void?Fun(A?a){}?

3 )???????? The object is returned from the function by passing the value.

?A?Fun(){A?a;Return?a;}??

3? Conversion Constructor

?? Similar to the copy constructor, there is only one parameter, but this parameter is not the type of this class but other types .?? A (B? A ){};? A? A; B? BA = B ;??? //?? Execute the conversion function? A (B )????

By restricted access

??

The constructor is generally of the Public type, but in special cases, the private type is used.

????

1? Singleton Mode

??? Privatize all constructors ???????? Code ;:? // Singleton. hclass? Singleton? {Public :??????? Static? Singleton *? Getinstance (); Private :??????? Singleton ()? {}??????? Static? Singleton? * Singleton;}; // singleton. cppsingleton *? Singleton: Singleton? =? NULL; Singleton *? Singleton: getinstance (){??????? If (Singleton? ==? Null )?????????????? Singleton? =? New? Singleton ();??????? Return? Singleton ;}?

2? Private copy constructor? Prevent default copy

?

What do you want to do ?? The constructor is copied during initialization, value transfer, and return value.

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Class ?. XML