copy constructor

Question

what is copy constructor? when, why we use copy constructor??

Ken H · Answer

Copy Constructor by the following two parts: 1)Shallow Copy Constructor; 2)Deep Copy Constructor. Shallow Copy Constructor is not the best approach,Because it will cause the application to crash. Examples 1: // Shallow Copy Constructor Demo. class MyClass{ public: MyClass(){ value = new int; *value = 123; } MyClass(const MyClass &obj){ cout value = obj.value; // Shallow copy field. } ~MyClass(){ delete value; value = NULL; } void print() const{ cout } void set(int i){ *value = i; } private: int *value; }; int main(void){ MyClass *mcObj= new MyClass(); cout mcObj->print(); // Will call Shallow Copy Constructor. MyClass mcObj2 = (*mcObj); cout mcObj2.print(); mcObj->set(456); cout mcObj2.print(); // Free the memory of mcObj. delete mcObj; // Trying to access the value of the field again. // However, that may cause the application to crash. mcObj2.print(); system("pause"); return 1; } Examples 2: // Deep Copy Constructor Demo. class MyClass{ public: MyClass(){ value = new int; *value = 123; } MyClass(const MyClass &obj){ cout value = new int; *value = *(obj.value); // Deep copy field. } ~MyClass(){ delete value; value = NULL; } void print() const{ cout } void set(int i){ *value = i; } private: int *value; }; int main(void){ MyClass *mcObj= new MyClass(); cout mcObj->print(); // Will call Deep Copy Constructor. MyClass mcObj2 = (*mcObj); cout mcObj2.print(); mcObj->set(456); cout mcObj2.print(); // Free the memory of mcObj. delete mcObj; // Trying to access the value of the field again. // Good,It is the results we expect, Print result is 123 mcObj2.print(); system("pause"); return 1; }

Rakesh · Answer

Hello, A Copy Constructor is a constructor that creates a new object by making a copy of an existing object. Example using System; using System.Text; namespace OPPS { class Constructor { class CopyConstructor { int a, b; public CopyConstructor(int i, int j) { a=i; b=j; } public CopyConstructor( CopyConstructor c) { a = c.a; b = c.b; } public void OutPut() { Console.WriteLine("Value of A = {0}",a); Console.WriteLine("Value of B = {0}", b); } } static void Main(string[] args) { CopyConstructor CC = new CopyConstructor(5,3); CopyConstructor copy = new CopyConstructor(CC); CC.OutPut(); Console.WriteLine("------- VALUE COPY ----------"); copy.OutPut(); Console.ReadLine(); } } } http://www.c-sharpcorner.com/UploadFile/b926a6/introduction-to-oops-in-C-Sharp/

Sujeet Suman · Answer

Copy Constructor: A constructor takes same class type as parameter is call copy constructor. It is used to instrantiate new intance with the same values of existing. class Test { // Copy constructor. public Test(Test previousTest) { Name = previousTest.Name; Age = previousTest.Age; } }

Gowtham K · Answer

Try this, http://www.onlinebuff.com/article_explain-the-copy-and-private-constructor-with-an-example-in-c_13.html http://www.aspdotnet-suresh.com/2013/09/csharp-copy-constructor-with-example.html

Manj N · Answer

i have one doubt in copy constructor class name { int a; public: name(int x) {a=x; } name(name &ob) { } }; void main() { name n1(2); name n2=n1; } when object is created memory is allocated for that object. Right? here 2 objects are created(n1 and n2). memory location of both n1 and n2 are same or different?

Rajeesh Menoth · Answer

Hi, Ref the following links.. 1) http://www.cplusplus.com/articles/y8hv0pDG/ 2) http://www.tutorialspoint.com/cplusplus/cpp_copy_constructor.htm 3) http://www.codeproject.com/Questions/205205/Why-we-need-the-Copy-Constructor-the-Assignment-Op

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