Custom Class Assignment Operator

Custom Class Assignment Operator-17
The difference between the copy constructor and assignment operator is that the copy constructor is a constructor — a function whose job it is to turn raw storage into an object of a specific class.

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If you don't want a class to be copied, for example, you have to define an empty copy constructor and assignment operator yourself and make them private or protected.

Furthermore, the compiler isn't guaranteed to create versions of these classes that do exactly what you want them to do.

This can be of any type, but the assignment operator that C automatically generates for you (and therefore, the one we're interested in here) is the one where you have the same type of object on both sides of the = sign.

That means the parameter is either an instance of or a reference to an instance of the same class as the object on the left-hand side.

This allows you to chain assignments together like so: ) would both still allow the simple chain described above to work, but have subtle differences in semantics from the way the standard operators do it that would come out in more complicated expressions involving assignment.

Returning a value also forces unnecessary trips through the object's copy constructor, costing you in performance.In my opinion, this goes to show you that working with C for a long time doesn't guarantee you really understand the language.Over this time, I've developed a stock interview question that's proven to be a pretty good gauge of C knowledge.So the outer shell of a properly-written assignment operator would look like this: should be a virtual function. Many C programmers are trained to make everything virtual, and in fact, some older frameworks do just that.In the specific example of the assignment operator, however, it's not a good idea.In C , these operations are expressed with the default constructor (e.g., ).These three functions are special in C : If you don't provide them yourself, C provides them for you. Among other things, this means you have to define these operations even if you don't want a client to be able to copy or default-construct a particular class.Another misconception I see often is a fuzzy idea of the difference between the copy constructor and the assignment operator.They're not the same thing, although they're similar. The copy constructor and assignment operator do similar things.For copying and assignment, for example, the automatically-generated code will do a shallow memberwise copy.If your class has pointer members, this is practically never what you want, and even when you don't have pointer members, this isn't always the right behavior. Even when the default versions of the special functions do what you want them to, it's still generally a good policy to always spell that out explicitly by writing them yourself.


Comments Custom Class Assignment Operator

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