Input and output functionality is not defined as part of the core C++ language, but rather is provided through the C++ standard library (and thus resides in the std namespace). In previous lessons, you included the iostream library header and made use of the cin and cout objects to do …
In previous lessons, we discussed that when passing an argument by value, a copy of the argument is made into the function parameter. For fundamental types (which are cheap to copy), this is fine. But copying is typically expensive for class types (such as std::string). We can avoid making an …
In all of the functions we’ve seen so far, the number of parameters a function will take must be known in advance (even if they have default values). However, there are certain cases where it can be useful to be able to pass a variable number of parameters to a …
The need for command line arguments As you learned in lesson , when you compile and link your program, the output is an executable file. When a program is run, execution starts at the top of the function called main(). Up to this point, we’ve declared main like this: int …
Pure virtual (abstract) functions and abstract base classes So far, all of the virtual functions we have written have a body (a definition). However, C++ allows you to create a special kind of virtual function called a pure virtual function (or abstract function) that has no body at all! A …
Consider the following program: #include <iostream> #include <string_view> class Base { public: std::string_view getName() const { return “Base”; } // not virtual virtual std::string_view getNameVirtual() const { return “Base”; } // virtual }; class Derived: public Base { public: std::string_view getName() const { return “Derived”; } virtual std::string_view getNameVirtual() const …
In this lesson and the next, we are going to take a closer look at how virtual functions are implemented. While this information is not strictly necessary to effectively use virtual functions, it is interesting. Nevertheless, you can consider both sections optional reading. When a C++ program is executed, it …
Virtual destructors Although C++ provides a default destructor for your classes if you do not provide one yourself, it is sometimes the case that you will want to provide your own destructor (particularly if the class needs to deallocate memory). You should always make your destructors virtual if you’re dealing …
In the previous lesson on pointers and references to the base class of derived objects, we took a look at a number of examples where using pointers or references to a base class had the potential to simplify code. However, in every case, we ran up against the problem that …
In the previous chapter, you learned all about how to use inheritance to derive new classes from existing classes. In this chapter, we are going to focus on one of the most important and powerful aspects of inheritance — virtual functions. But before we discuss what virtual functions are, let’s …
