assignment operator overloading in c

Question

I have used the following code for assignment operator overloading   SimpleCircle SimpleCircle  operator  const SimpleCircle  amp  rhs         if this     amp rhs          return  this       itsRadius   rhs getRadius         return  this      My Copy Constructor is this   SimpleCircle  SimpleCircle const SimpleCircle  amp  rhs        itsRadius   rhs getRadius        In the above operator overloading code  copy constructor is called as there is a new object is being created  hence I used the below code   SimpleCircle  amp  SimpleCircle  operator  const SimpleCircle  amp  rhs        if this     amp rhs         return  this      itsRadius   rhs getRadius        return  this      Its working perfectly and the copy constructor problem is avoided  but is there any unknown issues  to me  regarding this

User · Answer

Under the circumstances  you re almost certainly better off skipping the check for self-assignment -- when you re only assigning one member that seems to be a simple type  probably a double   it s generally faster to do that assignment than avoid it  so you d end up with   SimpleCircle  amp  SimpleCircle  operator  const SimpleCircle  amp  rhs        itsRadius   rhs getRadius       or just  itsRadius   rhs itsRadius       return  this      I realize that many older and or lower quality books advise checking for self assignment  At least in my experience  however  it s sufficiently rare that you re better off without it  and if the operator depends on it for correctness  it s almost certainly not exception safe    As an aside  I d note that to define a circle  you generally need a center and a radius  and when you copy or assign  you want to copy assign both

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include lt iostream gt   using namespace std   class employee       int idnum      double salary      public          employee              employee int a int b                        idnum a              salary b                     void dis                         cout lt  lt  1st emp   lt  lt endl lt  lt  idnum   lt  lt idnum lt  lt endl lt  lt  salary   lt  lt salary lt  lt endl lt  lt endl                     void operator  employee  amp emp                        idnum emp idnum              salary emp salary                     void show                         cout lt  lt  2nd emp   lt  lt endl lt  lt  idnum   lt  lt idnum lt  lt endl lt  lt  salary   lt  lt salary lt  lt endl                main         int a      double b       cout lt  lt  enter id num and salary  lt  lt endl      cin gt  gt a gt  gt b      employee e1 a b       e1 dis        employee e2      e2 e1      e2 show

User · Answer

The second is pretty standard  You often prefer to return a reference from an assignment operator so that statements like a   b   c  resolve as expected  I can t think of any cases where I would want to return a copy from assignment   One thing to note is that if you aren t needing a deep copy it s sometimes considered best to use the implicit copy constructor and assignment operator generated by the compiler than roll your own  Really up to you though      Edit   Here s some basic calls   SimpleCircle x     default constructor SimpleCircle y x      copy constructor x   y     assignment operator   Now say we had the first version of your assignment operator   SimpleCircle SimpleCircle  operator  const SimpleCircle  amp  rhs         if this     amp rhs          return  this     calls copy constructor SimpleCircle  this       itsRadius   rhs getRadius       copy member      return  this     calls copy constructor     It calls the copy constructor and passes a reference to this in order to construct the copy to be returned  Now in the second example we avoid the copy by just returning a reference to this  SimpleCircle  amp  SimpleCircle  operator  const SimpleCircle  amp  rhs        if this     amp rhs         return  this     return reference to this  no copy      itsRadius   rhs getRadius       copy member     return  this     return reference to this  no copy

User · Answer

There are no problems with the second version of the assignment operator  In fact  that is the standard way for an assignment operator   Edit  Note that I am referring to the return type of the assignment operator  not to the implementation itself  As has been pointed out in comments  the implementation itself is another issue  See here

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this might be helpful      Operator overloading in C     assignment operator overloading  include lt iostream gt  using namespace std   class Employee   private  int idNum  double salary  public  Employee           idNum   0  salary   0 0     void setValues  int a  int b   void operator   Employee  amp emp         void Employee  setValues   int idN   int sal      salary   sal  idNum   idN      void Employee  operator    Employee  amp emp      Assignment operator overloading function   salary   emp salary     int main        Employee emp1  emp1 setValues 10 33   Employee emp2  emp2   emp1     emp2 is calling object using assignment operator

User · Answer

it s right way to use operator overloading now you get your object by reference avoiding value copying

[c++] assignment operator overloading in c++

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