CSE 202 LAB 6

Modules, External Files

It is often more convenient to work on classes independantly by putting the code in separate files. To do this, you create an interface in a separate file, and the functions in an additional file. For example, lets consider the class Person.

Class definitions (interfaces) are stored in a header file, a file with the suffix .h

Create the class definition for the Person class in file Person.h as follows:

 #ifndef PERSON_H #define PERSON_H #include  using namespace std; class Person { public: Person(); Person(string fname, string lname, string cname); string getFirstName(); string getName(); string getLastName(); string getCompany(); private: string firstname; string lastname; string company; }; // Person #endif

The methods (member functions) of a class are stored in a file with the same name but with the suffix .cpp.

Complete the member function definitions in the file Person.cpp below. This file should begin with:

 #include "Person.h" #include  using namespace std; Person::Person() { firstname = ""; lastname = ""; company = ""; } // constructor

Note the difference between including string and Person.h

You can only compile and not run (link) Person.cpp because it does not contain a main() function. To compile, use the -c option of the compiler which produces an object file with the same name as the source code but with the suffix .o

g++ -c Person.cpp

This command produces Person.o

Now any program that needs to use a Person object can link to Person.o

You may test the correctness of your object file Person.o by creating yet another file which only includes the main() function and Person.h

Create the file PersonTest.cpp to contain:

 #include "Person.h" #include  #include  using namespace std; int main() { Person t("Bill", "Gates", "Microsoft"); cout << t.getName() << endl; cout << t.getCompany() << endl; }

Just compile:

g++ -c PersonTest.cpp

Just like before, this produces PersonTest.o

Link and name the executable PersonTest :

g++ PersonTest.o Person.o -o PersonTest

Run:

PersonTest

Make sure the output is what you expect!

Rather than having to compile each module at the command line, it will save time to use a makefile. A makefile lists the different compile and link instructions. The make file for building the above program looks like:

 PersonTest: PersonTest.o Person.o tabkey g++ PersonTest.o Person.o -o PersonTest Person.o: Person.cpp tabkey g++ -c Person.cpp PersonTest.o: PersonTest.cpp tabkey g++ -c PersonTest.cpp

Create and save your make file in the file PersonTest.make

Don't forget the second lines must start with a tab.

You may re-build the program every time you make any changes using the command:

make -f PersonTest.make

If you have time repeat the exercise by adding the class Location :

 class Location { public: Location(); Location(string addr, string bldg, string rm);) string getLocationAddress(); string getLocationBuilding(); string getLocationRoom(); private: string address; string building; string room; }; // Location