C ++ object-oriented basics, as well as some common interview correction questions.

1. constructor with default parameters (avoid using it in practice)

There will be ambiguity!

Class A {public: A (INT I = 10, Int J = 11, int K = 12); A (INT, INT); int I, j, k ;}; a: A (int A, int B, int c) {I = A; j = B; k = C;} A: A (int I, Int J) {This-> I = I; this-> J = J; this-> K = 100;} int main () {A; A A2 (20 ); A A3 (30,40); // error ambiguous call to overloaded function return 0 ;}

2. pointer to the object member function

Review the pointer variables of common functions:

INT (* p) (INT, INT );

The definition is divided into three parts: function type (* function pointer variable) (parameter Type 1, parameter type 2 ,......)

Void fun () {cout <"this is fun ()" <Endl ;}int main () {void (* p )(); // P is the pointer variable pointing to the void function p = fun; // assign the entry address of the fun function to the pointer Variable P, and P points to the function fun (* P) (); // call the fun function. Return 0 ;}

Defining a pointer variable pointing to an object member function is more complex.

An error occurred while writing it directly!

Class test {PRIVATE: int num; public: void getnum () {cout <num <Endl;} void setnum (INT num) {This-> num = num ;}}; int main () {test T; T. setnum (10); void (* p) (); // P is the pointer variable pointing to the void function p = T. getnum; // error! Error c2440: '=': cannot convert from 'void (_ thiscall test: *) (void) 'to 'void (_ cdecl *) (void) 'Return 0 ;}

Cause:

The most fundamental difference between a member function and a common function is that it is a member of a class. The compilation system requires that in the preceding copy statement, the pointer variable type must match the type of the function on the right of the value assignment.

Match in the following three aspects:

1) type and number of function parameters.

2) type of function return value

3) class.

3rd) Point mismatch! The following methods should be used:

This is really a pain! I know why Java is so popular, but I cannot afford to switch from Java to C ++.

Int main () {test T; T. setnum (10); // void (* p) (); // P is the pointer Variable Void (test: * p) () pointing to the void function )(); P = & test: getnum; // defines the public member function (T. * p) (); // call P to point to the test class public member function getnum (); Return 0 ;}