Constructors of base classes and derived classes

1. Call relationship of default constructor

The following example shows the call sequence between the base class and the derived constructor. Create a base class and then a derived class. When the object is destroyed, the derived class is first followed by the base class.

#include <iostream>#include <string>using namespace std;class CBase {    string name;    int age;public:    CBase() {        cout <<"BASE" << endl;    }    ~CBase() {        cout <<"~BASE" << endl;    }};class CDerive : public CBase {public:    CDerive() {         cout <<"DERIVE" << endl;    }    ~CDerive() {         cout <<"~DERIVE" << endl;    }};int main ( ) {    CDerive d;    return 0;}

 

Ii. parameter transfer

When a parameter exists, the parameter must be transmitted to the base class. Note the methods passed in the example (8th rows and 19th rows ).

#include<Iostream>#include<String>using namespaceSTD;classCbase {string name;public: Cbase (string S): Name (s) {cout <"Base :"<Name <Endl ;}~ Cbase () {cout <"~ Base"<Endl ;}};classCderive:publicCbase {intAge;public: Cderive (string s,intA): cbase (s), age (a) {cout <"Derive :"<Age <Endl ;}~ Cderive () {cout <"~ Derive"<Endl ;}};intMain () {cderive D ("Xiaoya", 27 );return0 ;}

 

3. parameter transfer for three generations of grandparents

When there are three layers of inheritance, parameters must be passed one by one (30th rows, 19th rows, 8th rows ).

#include<Iostream>#include<String>using namespaceSTD;classCbase {string name;public: Cbase (string S): Name (s) {cout <"Base :"<Name <Endl ;}~ Cbase () {cout <"~ Base"<Endl ;}};classCderive:publicCbase {intAge;public: Cderive (string s,intA): cbase (s), age (a) {cout <"Derive :"<Age <Endl ;}~ Cderive () {cout <"~ Derive"<Endl ;}};classCson:publicCderive {string ID;public: Cson (string S1,intA, string S2): cderive (S1, A), ID (S2) {cout <"Son :"<Id <Endl ;}~ Cson () {cout <"~ Son"<Endl ;}};intMain () {cson S ("Xiaoya", 27,"8503026");return0 ;}

 

Constructors of base classes and derived classes