TechCodeview

Konstruktor kopiranja je preopterećen konstruktor koji se koristi za deklariranje i inicijaliziranje objekta iz drugog objekta.

Konstruktor kopiranja ima dvije vrste:

Zadani konstruktor kopiranja:Prevodilac definira zadani konstruktor kopije. Ako korisnik ne definira konstruktor kopiranja, prevodilac isporučuje svoj konstruktor.Korisnički definirani konstruktor:Programer definira korisnički definirani konstruktor.

Sintaksa korisnički definiranog konstruktora kopiranja:

 Class_name(const class_name &old_object); 

Razmotrite sljedeću situaciju:

Rajinikanth

 class A { A(A &x) // copy constructor. { // copyconstructor. } } 

U gornjem slučaju, Konstruktor kopiranja može se pozvati na sljedeće načine:

Pogledajmo jednostavan primjer konstruktora kopiranja.

// program konstruktora kopije.

 #include using namespace std; class A { public: int x; A(int a) // parameterized constructor. { x=a; } A(A &amp;i) // copy constructor { x = i.x; } }; int main() { A a1(20); // Calling the parameterized constructor. A a2(a1); // Calling the copy constructor. cout&lt; <a2.x; return 0; } < pre> <p> <strong>Output:</strong> </p> <pre> 20 </pre> <h2>When Copy Constructor is called</h2> <p>Copy Constructor is called in the following scenarios:</p> <ul> <li>When we initialize the object with another existing object of the same class type. For example, Student s1 = s2, where Student is the class.</li> <li>When the object of the same class type is passed by value as an argument.</li> <li>When the function returns the object of the same class type by value.</li> </ul> <h2>Two types of copies are produced by the constructor:</h2> <ul> <li>Shallow copy</li> <li>Deep copy</li> </ul> <h2>Shallow Copy</h2> <ul> <li>The default copy constructor can only produce the shallow copy.</li> <li>A Shallow copy is defined as the process of creating the copy of an object by copying data of all the member variables as it is.</li> </ul> <p>Let&apos;s understand this through a simple example:</p> <pre> #include using namespace std; class Demo { int a; int b; int *p; public: Demo() { p=new int; } void setdata(int x,int y,int z) { a=x; b=y; *p=z; } void showdata() { std::cout &lt;&lt; &apos;value of a is : &apos; &lt; <a<< std::endl; std::cout << 'value of b is : ' < <b<< *p <<*p<< } }; int main() { demo d1; d1.setdata(4,5,7); d2="d1;" d2.showdata(); return 0; pre> <p> <strong>Output:</strong> </p> <pre> value of a is : 4 value of b is : 5 value of *p is : 7 </pre> <img src="//techcodeview.com/img/c-tutorial/75/c-copy-constructor-3.webp" alt="C++ Copy Constructor"> <p>In the above case, a programmer has not defined any constructor, therefore, the statement <strong>Demo d2 = d1;</strong> calls the default constructor defined by the compiler. The default constructor creates the exact copy or shallow copy of the existing object. Thus, the pointer p of both the objects point to the same memory location. Therefore, when the memory of a field is freed, the memory of another field is also automatically freed as both the fields point to the same memory location. This problem is solved by the <strong>user-defined constructor</strong> that creates the <strong>Deep copy</strong> .</p> <h2>Deep copy</h2> <p>Deep copy dynamically allocates the memory for the copy and then copies the actual value, both the source and copy have distinct memory locations. In this way, both the source and copy are distinct and will not share the same memory location. Deep copy requires us to write the user-defined constructor.</p> <p>Let&apos;s understand this through a simple example.</p> <pre> #include using namespace std; class Demo { public: int a; int b; int *p; Demo() { p=new int; } Demo(Demo &amp;d) { a = d.a; b = d.b; p = new int; *p = *(d.p); } void setdata(int x,int y,int z) { a=x; b=y; *p=z; } void showdata() { std::cout &lt;&lt; &apos;value of a is : &apos; &lt; <a<< std::endl; std::cout << 'value of b is : ' < <b<< *p <<*p<< } }; int main() { demo d1; d1.setdata(4,5,7); d2="d1;" d2.showdata(); return 0; pre> <p> <strong>Output:</strong> </p> <pre> value of a is : 4 value of b is : 5 value of *p is : 7 </pre> <img src="//techcodeview.com/img/c-tutorial/75/c-copy-constructor-4.webp" alt="C++ Copy Constructor"> <p>In the above case, a programmer has defined its own constructor, therefore the statement <strong>Demo d2 = d1;</strong> calls the copy constructor defined by the user. It creates the exact copy of the value types data and the object pointed by the pointer p. Deep copy does not create the copy of a reference type variable.</p> <h2>Differences b/w Copy constructor and Assignment operator(=)</h2> <table class="table"> <tr> <th>Copy Constructor</th> <th>Assignment Operator</th> </tr> <tr> <td>It is an overloaded constructor.</td> <td>It is a bitwise operator.</td> </tr> <tr> <td>It initializes the new object with the existing object.</td> <td>It assigns the value of one object to another object.</td> </tr> <tr> <td>Syntax of copy constructor: <br> Class_name(const class_name &amp;object_name) <br> { <br> // body of the constructor. <br> }</td> <td>Syntax of Assignment operator: <br> Class_name a,b; <br> b = a;</td> </tr> <tr> <td><ul> <li>The <strong>copy constructor</strong> is invoked when the new object is initialized with the existing object.</li> <li>The object is passed as an argument to the function.</li> <li>It returns the object.</li> </ul></td> <td>The <strong>assignment operator</strong> is invoked when we assign the existing object to a new object.</td> </tr> <tr> <td>Both the existing object and new object shares the different memory locations.</td> <td>Both the existing object and new object shares the same memory location.</td> </tr> <tr> <td>If a programmer does not define the copy constructor, the compiler will automatically generate the implicit default copy constructor. </td> <td>If we do not overload the &apos;=&apos; operator, the bitwise copy will occur.</td> </tr> </table> <hr></a<<></pre></a<<></pre></a2.x;>

Kada se pozove Copy Constructor

Konstruktor kopiranja poziva se u sljedećim scenarijima:

math.pow java

• Kada inicijaliziramo objekt s drugim postojećim objektom istog tipa klase. Na primjer, Student s1 = s2, gdje je Student klasa.
• Kada se objektu istog tipa klase proslijedi vrijednost kao argument.
• Kada funkcija vrati objekt istog tipa klase po vrijednosti.

Konstruktor proizvodi dvije vrste kopija:

• Plitka kopija
• Duboka kopija

Plitka kopija

• Zadani konstruktor kopije može proizvesti samo plitku kopiju.
• Plitka kopija definirana je kao proces stvaranja kopije objekta kopiranjem podataka svih varijabli članova kakvi jesu.

Shvatimo ovo kroz jednostavan primjer:

 #include using namespace std; class Demo { int a; int b; int *p; public: Demo() { p=new int; } void setdata(int x,int y,int z) { a=x; b=y; *p=z; } void showdata() { std::cout &lt;&lt; &apos;value of a is : &apos; &lt; <a<< std::endl; std::cout << \'value of b is : \' < <b<< *p <<*p<< } }; int main() { demo d1; d1.setdata(4,5,7); d2="d1;" d2.showdata(); return 0; pre> <p> <strong>Output:</strong> </p> <pre> value of a is : 4 value of b is : 5 value of *p is : 7 </pre> <img src="//techcodeview.com/img/c-tutorial/75/c-copy-constructor-3.webp" alt="C++ Copy Constructor"> <p>In the above case, a programmer has not defined any constructor, therefore, the statement <strong>Demo d2 = d1;</strong> calls the default constructor defined by the compiler. The default constructor creates the exact copy or shallow copy of the existing object. Thus, the pointer p of both the objects point to the same memory location. Therefore, when the memory of a field is freed, the memory of another field is also automatically freed as both the fields point to the same memory location. This problem is solved by the <strong>user-defined constructor</strong> that creates the <strong>Deep copy</strong> .</p> <h2>Deep copy</h2> <p>Deep copy dynamically allocates the memory for the copy and then copies the actual value, both the source and copy have distinct memory locations. In this way, both the source and copy are distinct and will not share the same memory location. Deep copy requires us to write the user-defined constructor.</p> <p>Let&apos;s understand this through a simple example.</p> <pre> #include using namespace std; class Demo { public: int a; int b; int *p; Demo() { p=new int; } Demo(Demo &amp;d) { a = d.a; b = d.b; p = new int; *p = *(d.p); } void setdata(int x,int y,int z) { a=x; b=y; *p=z; } void showdata() { std::cout &lt;&lt; &apos;value of a is : &apos; &lt; <a<< std::endl; std::cout << \'value of b is : \' < <b<< *p <<*p<< } }; int main() { demo d1; d1.setdata(4,5,7); d2="d1;" d2.showdata(); return 0; pre> <p> <strong>Output:</strong> </p> <pre> value of a is : 4 value of b is : 5 value of *p is : 7 </pre> <img src="//techcodeview.com/img/c-tutorial/75/c-copy-constructor-4.webp" alt="C++ Copy Constructor"> <p>In the above case, a programmer has defined its own constructor, therefore the statement <strong>Demo d2 = d1;</strong> calls the copy constructor defined by the user. It creates the exact copy of the value types data and the object pointed by the pointer p. Deep copy does not create the copy of a reference type variable.</p> <h2>Differences b/w Copy constructor and Assignment operator(=)</h2> <table class="table"> <tr> <th>Copy Constructor</th> <th>Assignment Operator</th> </tr> <tr> <td>It is an overloaded constructor.</td> <td>It is a bitwise operator.</td> </tr> <tr> <td>It initializes the new object with the existing object.</td> <td>It assigns the value of one object to another object.</td> </tr> <tr> <td>Syntax of copy constructor: <br> Class_name(const class_name &amp;object_name) <br> { <br> // body of the constructor. <br> }</td> <td>Syntax of Assignment operator: <br> Class_name a,b; <br> b = a;</td> </tr> <tr> <td><ul> <li>The <strong>copy constructor</strong> is invoked when the new object is initialized with the existing object.</li> <li>The object is passed as an argument to the function.</li> <li>It returns the object.</li> </ul></td> <td>The <strong>assignment operator</strong> is invoked when we assign the existing object to a new object.</td> </tr> <tr> <td>Both the existing object and new object shares the different memory locations.</td> <td>Both the existing object and new object shares the same memory location.</td> </tr> <tr> <td>If a programmer does not define the copy constructor, the compiler will automatically generate the implicit default copy constructor. </td> <td>If we do not overload the &apos;=&apos; operator, the bitwise copy will occur.</td> </tr> </table> <hr></a<<></pre></a<<>

U gornjem slučaju, programer nije definirao nikakav konstruktor, dakle, naredbu Demo d2 = d1; poziva zadani konstruktor definiran od strane prevoditelja. Zadani konstruktor stvara točnu kopiju ili plitku kopiju postojećeg objekta. Dakle, pokazivač p oba objekta pokazuje na istu memorijsku lokaciju. Stoga, kada se memorija polja oslobodi, memorija drugog polja također se automatski oslobađa budući da oba polja pokazuju na istu memorijsku lokaciju. Ovaj problem je riješen pomoću korisnički definiran konstruktor koji stvara Duboka kopija .

Duboka kopija

Duboka kopija dinamički dodjeljuje memoriju za kopiju i zatim kopira stvarnu vrijednost, i izvor i kopija imaju različite memorijske lokacije. Na taj su način i izvor i kopija različiti i neće dijeliti istu memorijsku lokaciju. Duboka kopija zahtijeva da napišemo korisnički definirani konstruktor.

Shvatimo ovo kroz jednostavan primjer.

 #include using namespace std; class Demo { public: int a; int b; int *p; Demo() { p=new int; } Demo(Demo &amp;d) { a = d.a; b = d.b; p = new int; *p = *(d.p); } void setdata(int x,int y,int z) { a=x; b=y; *p=z; } void showdata() { std::cout &lt;&lt; &apos;value of a is : &apos; &lt; <a<< std::endl; std::cout << \'value of b is : \' < <b<< *p <<*p<< } }; int main() { demo d1; d1.setdata(4,5,7); d2="d1;" d2.showdata(); return 0; pre> <p> <strong>Output:</strong> </p> <pre> value of a is : 4 value of b is : 5 value of *p is : 7 </pre> <img src="//techcodeview.com/img/c-tutorial/75/c-copy-constructor-4.webp" alt="C++ Copy Constructor"> <p>In the above case, a programmer has defined its own constructor, therefore the statement <strong>Demo d2 = d1;</strong> calls the copy constructor defined by the user. It creates the exact copy of the value types data and the object pointed by the pointer p. Deep copy does not create the copy of a reference type variable.</p> <h2>Differences b/w Copy constructor and Assignment operator(=)</h2> <table class="table"> <tr> <th>Copy Constructor</th> <th>Assignment Operator</th> </tr> <tr> <td>It is an overloaded constructor.</td> <td>It is a bitwise operator.</td> </tr> <tr> <td>It initializes the new object with the existing object.</td> <td>It assigns the value of one object to another object.</td> </tr> <tr> <td>Syntax of copy constructor: <br> Class_name(const class_name &amp;object_name) <br> { <br> // body of the constructor. <br> }</td> <td>Syntax of Assignment operator: <br> Class_name a,b; <br> b = a;</td> </tr> <tr> <td><ul> <li>The <strong>copy constructor</strong> is invoked when the new object is initialized with the existing object.</li> <li>The object is passed as an argument to the function.</li> <li>It returns the object.</li> </ul></td> <td>The <strong>assignment operator</strong> is invoked when we assign the existing object to a new object.</td> </tr> <tr> <td>Both the existing object and new object shares the different memory locations.</td> <td>Both the existing object and new object shares the same memory location.</td> </tr> <tr> <td>If a programmer does not define the copy constructor, the compiler will automatically generate the implicit default copy constructor. </td> <td>If we do not overload the &apos;=&apos; operator, the bitwise copy will occur.</td> </tr> </table> <hr></a<<>

U gornjem slučaju, programer je definirao vlastiti konstruktor, dakle iskaz Demo d2 = d1; poziva konstruktor kopiranja definiran od strane korisnika. Stvara točnu kopiju podataka tipa vrijednosti i objekta na koji pokazuje pokazivač p. Duboka kopija ne stvara kopiju varijable referentnog tipa.

Razlike c/w Konstruktor kopiranja i operator dodjele (=)