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Chapter 23: A New Assignment Operator, Should You Decide to Accept It 307Creating Shallow CopiesIs a Deep ProblemNo matter what anyone may think of operator overloading, you will need tooverload the assignment operator for many classes that you generate. C++provides a default definition for operator=() for all classes. This default definitionperforms a member-by-member copy. This works great for an intrinsictype like an int.int i;i = 10;// “member by member” copyThis same default definition is applied to user-defined classes. In the followingexample, each member of source is copied over the correspondingmember in destination.void fn(){MyStruct source, destination;destination = source;}The default assignment operator works for most classes; however, it is notcorrect for classes that allocate resources, such as heap memory. The programmermust overload operator=() to handle the transfer of resources.The assignment operator is much like the copy constructor. In use, the twolook almost identical:void fn(MyClass &mc){MyClass newMC(mc); // of course, this uses the// copy constructorMyClass newerMC = mc;// less obvious, this also invokes// the copy constructor}MyClass newestMC;newestMC = mc;// this creates a default object// and then overwrites it with// the argument passedThe creation of newMC follows the standard pattern of creating a new object asa mirror image of the original using the copy constructor MyClass(MyClass&).Not so obvious is that newerMC is also created using the copy constructor.