Object-Oriented Programming-c++_ class 26 copy construction ⅰ_ 27 copy Construction Ⅱ

Copy constructor, not byte-to-byte copy, but member-to-member copy

constructor, a parameter is a reference to a class

That's right

1#include <iostream>2#include <string>3 using namespacestd;4 5 Static intObjectcount =0;6 7 classHowmany8 {9  Public:TenHowmany () {objectcount++; print ("Howmany ()"); }//constructor, no arguments OneHowmany (inti) {objectcount++; print ("howmany (int)"); }//constructor, the argument is an int AHowmany (Consthowmany& o) {objectcount++; print ("Howmany (HM)"); }//constructor, a parameter is a reference to a class -     voidPrintConst string& msg ="") -     { the         if(Msg.size ()! =0) -         { -Std::cout << msg <<": "; -         } +Std::cout <<"objectcount=" -<< Objectcount <<Std::endl; +     } A~Howmany () at     { -objectcount--; -Print"~howmany ()"); -     } - }; -  in Howmany F (howmany x) - { toStd::cout <<"begin of F"<<Std::endl; +X.print ("x argument inside F ()"); -Std::cout <<"end of F"<<Std::endl; the     returnx; * } $ Panax Notoginseng voidMain () - { the Howmany H; +H.print ("After construction of H"); A      theHowmany H2 =f (h); +     //howmany h2 = h; -     //Howmany H2 (ten);//constructor, the argument is an int $     //howmany H2 (h);//constructor, parameter is a class $  -H.print ("After call to F ()"); -      theSystem"Pause"); -}

constructor, parameter is a new class that forms a dead loop

Error

1>main.cpp: Error C2652: "Howmany": illegal copy constructor: The first argument should not be "howmany"
1> main.cpp (8): note: see Declaration of "Howmany"
1>main.cpp: Error C2333: "Howmany::howmany": There are errors in the function declaration; Skip function Body
1>main.cpp: Error C2440: "Return": Cannot convert from "Howmany" to "Howmany"
1> main.cpp: Note: The construction class "Howmany" cannot be copied because the copy constructor is ambiguous or no copy constructor is available
1>main.cpp: Error C2664: "Howmany F (howmany)": cannot convert parameter 1 from "Howmany" to "Howmany"
1> main.cpp: Note: The construction class "Howmany" cannot be copied because the copy constructor is ambiguous or no copy constructor is available

1#include <iostream>2#include <string>3 using namespacestd;4 5 Static intObjectcount =0;6 7 classHowmany8 {9  Public:TenHowmany () {objectcount++; print ("Howmany ()"); }//constructor, no arguments OneHowmany (inti) {objectcount++; print ("howmany (int)"); }//constructor, the argument is an int A  -Howmany (Howmany o) {objectcount++; print ("Howmany (HM)"); }//constructor, error, parameter is a new class that forms a dead loop -  the     //1>main.cpp: Error C2652: "Howmany": illegal copy constructor: The first argument should not be "Howmany" -     //1> main.cpp (8): note: see Declaration of "Howmany" -     //1>main.cpp: Error C2333: "Howmany::howmany": There are errors in the function declaration; Skip function Body -     //1>main.cpp: Error C2440: "Return": Cannot convert from "Howmany" to "Howmany" +     //1> main.cpp: Note: The construction class "Howmany" cannot be copied because the copy constructor is ambiguous or no copy constructor is available -     //1>main.cpp: Error C2664: "Howmany F (howmany)": cannot convert parameter 1 from "Howmany" to "Howmany " +     //1> main.cpp: Note: The construction class "Howmany" cannot be copied because the copy constructor is ambiguous or no copy constructor is available A  at     voidPrintConst string& msg ="") -     { -         if(Msg.size ()! =0) -         { -Std::cout << msg <<": "; -         } inStd::cout <<"objectcount=" -<< Objectcount <<Std::endl; to     } +~Howmany () -     { theobjectcount--; *Print"~howmany ()"); $     }Panax Notoginseng }; -  the Howmany F (howmany x) + { AStd::cout <<"begin of F"<<Std::endl; theX.print ("x argument inside F ()"); +Std::cout <<"end of F"<<Std::endl; -     returnx; $ } $  - voidMain () - { the Howmany H; -H.print ("After construction of H");Wuyi      theHowmany H2 =f (h); -     //howmany h2 = h; Wu     //Howmany H2 (ten);//constructor, the argument is an int -     //howmany H2 (h);//constructor, parameter is a class About  $H.print ("After call to F ()"); -      -System"Pause"); -}

Object-Oriented Programming-c++_ class 26 copy construction ⅰ_ 27 copy Construction Ⅱ