C + + Construction and destruction-10

One. Initialization of the object

1. All objects in general need a definite initial state

2. Solution

A. Provides a public initialize function for each class-even read

B. Immediately after the object is created, call the Initialize function to initialize

#include <stdio.h>classtest{Private:       inti;  Public:       voidInitialize () {i=0; }            intGet1 () {returni; }};intMain () {Test T1;    Test T2;        Test T3;    T1.initialize ();    T2.initialize ();        T3.initialize (); printf ("ti.i =%d\n", T1.get1 ()); printf ("ti.i =%d\n", T1.get1 ()); printf ("ti.i =%d\n", T1.get1 ()); printf ("Press any key to continue");    GetChar (); return 0; }

3.initialize is just a normal function that must show the call

4. Once the object is not initialized due to a mistake, the result will be indeterminate

An object with no initialization, the value of its internal member variable is constant.

Two. Constructors in C + +

1. A class in C + + can define a special member function that is the same as the class name.

2. This member function, which is the same as the class name, is called a constructor

3. Constructors can have parameters when they are defined, but there is no declaration of any return type

4. Calls to constructors

A. In general, the C + + compiler automatically calls constructors

B. Functions that need to be called manually in some cases

#include <stdio.h>classtest{Private:       inti; intJ; intK;  Public: Test (intv) {i= j = k =v; }        voidprint () {printf ("i =%d,j =%d,k =%d\n", i,j,k); }};intMain () {Test T1 (4); Test T2=5; Test T3= Test (6);;    T1.print ();    T2.print ();        T3.print (); Test ta[3] = {Test (1), Test (2), Test (3)};  for(intI=0;i<3; i++) {ta[i].print (); } printf ("Press any key to continue");    GetChar (); return 0; }

5. Two special constructors

#include <stdio.h>/*
Attention:
1. When no constructors are defined in a class, the C + + compiler provides a parameterless constructor and copy constructor
2. When any non-copy constructor is defined in a class, the C + + compiler does not provide us with an parameterless constructor
*/classtest{Private:       inti; intJ; intK;  Public: Test (Consttest&v) {printf ("Test (const test& v) \ n"); } Test () {printf ("Test () \ n"); }        };intMain () {Test T1; Test T2=T1; printf ("Press any key to continue");    GetChar (); return 0; }

A. Non-parametric constructors

When a constructor is not defined in a class, the compiler provides an parameterless constructor by default, and its function body is empty

B. Copy Constructors

When a copy constructor is not defined in a class, the compiler provides a copy constructor by default, which simply replicates the value of the member variable

Three. Array class

Array.h

#ifndef _array_h_#define_array_h_classarray{Private:   intmlength; int*Mspace; Public: Array (intlength); Array (Constarray&obj); intlength (); voidSetData (intIndexintvalue); intGetData (intindex); voiddestory (); };#endif

Array.c

#include"Array.h"Array::array (intLength//Array Creation{    if(Length <0) {length=0; } mlength=length; Mspace=New int[mlength];} Array::array (Constarray&obj) {Mlength=obj.mlength; Mspace=New int[Mlength];  for(intI=0; i<mlength; i++) {Mspace[i]=Obj.mspace[i]; } }intArray::length ()//Array Size{    returnmlength; }voidArray::setdata (intIndexintValue//Setting Array Values{Mspace[index]=value; }intArray::getdata (intIndex//Get Array Values{    returnMspace[index];}voidArray::d estory ()//Destroying Space{mlength= -1; Delete[] mspace; }

Main.c

#include <stdio.h>#include"Array.h"intMain () {Array A1 (Ten);  for(intI=0; I<a1.length (); i++) {a1.setdata (i,i); }         for(intI=0; I<a1.length (); i++) {printf ("element%d:%d\n", I,a1.getdata (i)); } Array A2=A1;  for(intI=0; I<a2.length (); i++) {printf ("element1%d:%d\n", I,a2.getdata (i));    } a1.destory ();        A2.destory (); printf ("Press any key to continue");    GetChar (); return 0; }

Output results

　　

C + + Construction and destruction-10