C + + operator overloading (ii)

About overloads of the input (CIN)/output (cout).

In the header file of C + + has #include <iostream>, actually contains cin/cout, specifically: ostream corresponds to cout, and IStream corresponds to CIN.

I first implement the cout overload

#include <iostream>using namespace Std;class oc{public:private:int cnt;public:oc (int cnt) {this-    >cnt = CNT; } Friend ostream& operator << (ostream& ost, const oc& Oc);};o    stream& operator << (ostream& ost, const oc& Oc) {ost << oc.cnt; return OST;}    int main () {System ("color 5A");    OC OC (2);    cout << OC; return 0;}

Operation Result:

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Explain:

①: Parameter ostream& ost, const oc& Oc, and return ostream& are all using references to prevent the call copy construct

②: Can be returned using void, but cannot use continuous output << oc << XXX

③: The left operand must be a Ostream object, so this overload must be implemented outside of the class

CIN Overloads:

#include  <iostream>using namespace std;class oc{private:    int  cnt;public:    oc ( int cnt)     {         this->cnt = cnt;    }     Friend istream& operator >> (&NBSP;ISTREAM&AMP;&NBSP;IST&NBSP;,&NBSP;OC&AMP;&NBSP;OC);     friend int main ();}; Istream& operator >> (&NBSP;ISTREAM&AMP;&NBSP;IST&NBSP;,&NBSP;OC&AMP;&NBSP;OC) {     ist >> oc.cnt;    if ( ist.fail ()  )      {        cout <<  "fail value to  Oc.cnt! "  << endl;        oc.cnt = 0;     }    return ist;} Int main () {    system ("color 5a");     oc oc (2);     cin >> oc;    cout <<  "OC.CNT&NBSP;VALUE&NBSP;IS&NBSP;:   "&NBSP;&LT;&LT;&NBSP;OC.CNT&NBSP;&LT;&LT;&NBSP;ENDL;&NBSP;&NBSP;&NBSP;&NBSP;RETURN&NBSP;0;}

①, I first enter the correct value such as 1, the result is as follows:

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②, enter a string in the wrong value. The results are as follows:

650) this.width=650; "title=" 03.png "src=" https://s5.51cto.com/wyfs02/M00/96/6B/ Wkiom1khfqlgmarmaaa162yd6pi317.png-wh_500x0-wm_3-wmp_4-s_1771697362.png "alt=" Wkiom1khfqlgmarmaaa162yd6pi317.png-wh_50 "/>

Ist.fail () is used to detect if the input failed. The string cannot be assigned a value for int. So---

CIN, like cout, can only be implemented outside the class.

This article is from the "Better_power_wisdom" blog, make sure to keep this source http://aonaufly.blog.51cto.com/3554853/1927956

C + + operator overloading (ii)