The University of Iowa
The College of Liberal Arts and Sciences
Department of Computer Science
Programming Languages and Tools:
CS:3210:0001
Lecture/Lab #12
Programming with C++
Inheritance, (run-time) polymorphism
Warm up
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How do you define a class member function outside of the class definition itself?
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Is the following a valid C++ program?
struct resource;
struct lock
{
struct key {}; // can we nest types?
lock( resource& r ) : r_( r ) {}
resource& unlock( key const& ) { return r_; }
private:
resource& r_;
};
struct car
{
car( std::string const& make ) : make( make ) {}
void start() { std::cout << "Starting...\n"; }
std::string const make;
};
Exercise 1
Define all class member functions and types outside of the provided class definition
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Open the exercise template
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Write your code, press Run to test
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When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
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Click on the corresponding option in the "Lab12 exercises" poll in #general
Inheritance 101
struct car {
car( std::string const& make,
std::string const& model,
int year );
std::string make;
std::string model;
int year;
};
struct truck : car { // truck is-a car
truck( std::string const& make,
std::string const& model,
int year, double capacity );
double capacity;
};
Inheritance summary
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Public inheritance establishes is-a relationship between base and derived classes.
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A reference to a derived class is implicitly convertible to a reference to a base class.
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Base class constructor is called (implicitly or explicitly) as a part of the derived class constructor.
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Base class constructor is called before other data members of the derived class are initialized.
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An instance of a base class can be explicitly cast to a derived class using static_cast; if the cast instance isn't in fact a part of the derived object, the cast results in undefined behavior.
Exercise 2
Complete the class hierarchy as outlined in the exercise's comments
-
Open the exercise template
-
Write your code, press Run to test
-
When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab12 exercises" poll in #general
(Run-rime) Polymorphism
struct car {
car( std::string const& make,
std::string const& model,
int year );
void print( std::ostream& ) const;
};
struct truck : car { // truck is-a car
truck( std::string const& make,
std::string const& model,
int year, double capacity );
void print( std::ostream& ) const;
};
std::ostream& operator<<( std::ostream& out, car const& c ) {
c.print( out );
return out;
}
Programming with C++, Fall 2019, Lecture #12
By Aleksey Gurtovoy
Programming with C++, Fall 2019, Lecture #12
Inheritance, (run-time) polymorphism
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