A9-Getting Classy

Table of Contents


Objectives

  • Develop classes and construct objects.
  • Hide data using the keyword private.
  • Write member functions that access private data.
  • Code multiple constructors to initialize private data.
  • Call member functions of objects.

Academic Honesty

Read the Scholastic Honesty Policy and Assignment Integrity policies of the syllabus. Here are some clarifications for this particular assignment:

  • You are encouraged to work with one other student of this class following the rules of Pair Programming for Homework Assignments. If you choose to pair program, there is a bonus applied.
  • You may not give a copy of your code to your designated pair-programming partner if you did not develop the code together.
  • You may not look at another student's code until you complete and submit this assignment, except for code you develop code together with your pair-programming partner.
  • You may get help from people other than your pair-programming partner if you get stuck, but only if they do not show or tell you the code to type.

Preparation

  1. Make sure you have completed the exercises from lesson 9.
  2. Complete the Review Exercises in CodeLab 9. These exercises will help prepare you for the problem-solving programs and should be completed first.

Project Specifications

Your solutions to these projects must use only techniques we have covered so far.

Programming Style

For all programs, remember to follow all the style rules we have covered, as well as the new rules, including:

  1. Class naming conventions (See: Class Names) new!
  2. Indentation in classes and placement of curly braces new!
  3. Every function declaration (prototype) in the class, including constructor functions, have a function comment block new!
  4. Every file has a file comment block
  5. No magic numbers (See: No Magic Numbers)

Hamster
Image source

Project 1: A Classy Hamster

Hamsters are furry rodents that are often kept as pets. They feed primarily on seeds, fruits, and vegetation, and will occasionally eat burrowing insects [1]. Hamsters are weaned after 3-4 weeks [2] and have a life span of 1.5 to 3.5 years [3].

Most hamster pets are kept in cages. The cages often contain an exercise wheel and hamsters are highly motivated to run in wheels [4].

Project Specifications
  1. Write a declaration and a definition for a class named Hamster along with a short main() function to test the class code. See lesson 9.2.2 to get started.
  2. Name the source code file hamster.cpp and include all your code in this single file.

    Be careful of the spelling, including capitalization, as you will lose points for a misspelled name. Naming is important in programming.

  3. Have no user input for this project. Testing code for the program is hard-coded in main().

    Do NOT use any keyboard input streams, like cin, in this project. If you have a cin statement in your code, you will get a low score.

  4. The Hamster class must contain exactly (no more and no less than) two member variables declared private:
    1. string name
    2. int age in months
    See lesson 9.2.3 for an example.
  5. Write function declarations (prototypes) inside the class and separately define (implement) all the member functions outside the class declaration (curly braces of the class), including constructor functions.
  6. Write a default constructor that sets the name to "Cheeky" and the age to 1. See lesson 9.2.5 for an example.
  7. Write a two-parameter constructor that sets the name and age member variables to the parameter values. The parameters must be coded in the order of name followed by age. See lesson 9.3.2 for examples.
  8. Write one "get" function for each of the member variables that returns the variable's current value. The name of the function must follow the naming standards for "get" functions, which is the name of the variable with the prefix word "get". See lesson 9.3.4 for examples.
  9. All non-mutator functions must include the keyword const as discussed in lesson 9.3.4 under Accessor Functions and in the textbook on pages 402-403 under the section on, "const Correctness".
  10. Write a member function for the Hamster class named say() with the following signature:
    /**
        Randomly selects a single sound from the sounds array.
    
        @param sounds An array of sounds to choose from.
        @param size The number of elements in the array.
        @return A randomly selected sound from the list of sounds.
    */
    string say(string sounds[], int size) const;
    

    Call the function at least once in your story. When called, the function selects one of the sounds from the array parameter at random and returns one of the sounds made by a Hamster. The four sounds made by a Hamster for this project are: "chatter", "chirp", "squeal", and "squeak". All are printed without the double quotes.

  11. Example Run: In your main() function, construct two or more Hamster objects, using both the default constructor and the overloaded constructor. Then write a story that calls all the member functions of the class at least one time. For example:
    Meet my new Hamster Cheeky who is 1 month old.
    My older hamster, Buster spends most of his time running in his big wheel.
    My new hamster Cheeky knows three things:
    1. How to eat. Show them Cheeky: chomp
    2. How to talk. Show them Cheeky: squeak
    3. How to sleep. Show them Cheeky: Zzzz!
    

    In the above example story, the text in aqua italics shows the output of member functions calls. Your program does NOT print the characters using colors or italics. Have fun and make up your own hamster story. See lessons 9.2.3 and 9.3.3 for how to construct objects from classes. See lesson 9.3.4 on how to access member variables.

  12. After displaying the story, exit the program.
  13. Submit this project with the rest of the assignment as described in Deliverables.
Hints:
  • We only need the functions listed in the specifications above, though there is no penalty for adding more functions in this project. However, consider if another function is actually needed before adding one. Best practice is to minimize the functions provided.
  • To make a hamster say different things every time the program runs, see lesson 7.3.4: Seeding the Random Generator.
References and More Information
  1. Hamster: Wikipedia article.
  2. How Soon Can You Take a Hamster From Its Mother?: animals.mom.me
  3. How long do hamsters live?: The Hamster House
  4. Hamster wheel: Wikipedia article.

♯♪ ♬

Project 2: A Class Song

In this project we create a simple class for a song database. A song is a musical composition of words and music [1]. Many of us have playlists of recorded songs that we keep on music players or phones.

When we declare a class, we create a model of an object in software. Songs are complex and to be efficient, we create an abstraction of what we are modeling. Abstraction is the reduction of a concept or idea to the most simple or basic of shared characteristics. Once we develop a class, we may create many objects from the class.

Our class Song will contain the information we need to store a song in our database and a programming interface to access the song data. In addition we will write a short main() function to test our code.

Project Specifications
  1. Write a declaration and a definition for a class named Song along with a short main() function to test the class code.
  2. Name the source code file song.cpp and include all your code in this single file.

    Be careful of the spelling, including capitalization, as you will lose points for a misspelled name. Naming is important in programming.

  3. Have no user input for this project. Testing code for the program is hard-coded in main().

    Do NOT use any keyboard input streams, like cin, in this project. If you have a cin statement in your code, you will get a low score.

  4. The Song class must contain exactly (no more and no less than) four member variables declared private:
    1. string title
    2. string artist
    3. double rating (1.0 to 5.0)
    4. int length (in seconds)
  5. Declare only the following functions (prototypes) inside the class braces and separately define (implement) the functions outside the class declaration (curly braces of the class):
    1. A default constructor that sets the numerical types to zero (0).
    2. A four-parameter constructor that sets the title, artist, rating, and length member variables to the parameter values. The parameters must be coded in the order of title, , artist, rating, and length.
    3. One "get" function for each of the member variables that returns the variable's current value. The name of the function must follow the naming standards for "get" functions, which is the name of the variable with the prefix word "get". Include the const keyword.
    4. One "set" function for each member variable with a single parameter that sets a value for a member variable. The name of the function must follow the naming standards for "set" functions, which is the name of the variable with the prefix "set".
    5. Accessor function print() that has no parameters and returns no values, but displays the data of the object all on one line like this:
      Happier               Marshmello                 4.4    3:34
      Text must be left justified and numbers right justified with the correct number of decimal places. To ensure the correct number of decimal places for any number use both fixed and setprecision() in print(). The data displayed in order are:
      1. title
      2. artist
      3. rating
      4. length in minutes:seconds

      Convert length to minutes and seconds as shown. End the printing with a newline.

    6. Do not add any extra member functions beyond the above.

    Note: even though you must write the get functions, you may not need to actually call them for this assignment. We will be using the get functions in future assignments.

  6. All non-mutator functions must include the keyword const as discussed in lesson 9.2.4 under Accessor Functions and in the textbook on pages 402-403 under the section on "const Correctness".
  7. In the song.cpp file, write a main() function to do the following:
    1. Construct at least three Song objects.
    2. Set values (title, artist, rating, and length) for one or more objects using the four-parameter constructor, and for one or more objects using the default constructor followed by calling all the "set" functions to assign values. Make certain one rating has a decimal place of zero (.0) to verify correct alignment.
    3. Display output for all 3+ objects as shown in the Example Output specification including the column headings.

    Have no user input for this project. Instead write code to do the above in main() for testing. Do NOT use any keyboard input streams, like cin, in this project. If you have a cin statement in your code, you will get a low score.

  8. Example Run: When you run the program you must see the following output without any user input.
    Famous Song List:
    Title                 Artist/Band             Rating  Length
    Happier               Marshmello                 4.4    3:34
    Without Me            Halsey                     3.8    3:21
    Head Above Water      Avril Lavigne              5.0    3:40
    

    You may change the spacing between columns but columns must line up as shown, with names left justified and numbers right justified. Feel free to come up with your own song names and other data.

  9. Create the correct spacing for the output using the setw() formatting manipulator described on pages 49-51 (1/e: 53-55) of the textbook. In addition, use the formatting manipulator left for text and right for numbers to ensure correct alignment for all data. To make use of these manipulators include the iomanip library. For example:
    cout << setw(22) << left << title; // aligns data left in 22 character field
    
  10. After displaying the output, exit the program.
  11. Submit the source code file song.cpp with the rest of the assignment as described in Deliverables.
Hints:
  • The width constants in the example run are
    const int TITLE_WIDTH = 22;
    const int ARTIST_WIDTH = 22;
    const int RATING_WIDTH = 8;
    const int LENGTH_WIDTH = 8;
    
  • Do NOT put const variables inside the class. See spec 4 above.
  • To print leading zeros for the seconds in a song, test if the number of seconds is less than 10 and print a '0'. Another way, is to use the setfill() manipulator function.
References and More Information
  1. Song: definition by Merriam-Webster

Extra Credit

The following are worth extra credit points if the main program works well:

  1. Complete the assignment using pair programming. (2 points)
  2. Add a function named toString() to class Song that has no parameters and returns a string containing all the data about the movie. Call the function one time to show that it works. (2 points)

    The function does NOT print any values and must NOT use cout. Instead, the function must return a string with one line of text like that shown below.

    Happier               Marshmello                 4.4    3:34
    

    Once returned, print the string within main() using code like:

    cout << happier.toString() << endl;
    

    Note that this extra credit will require you to convert numbers to strings. Research stringstream for the conversion and provide an attribution for the source of your stringstream information, either a URL or book and page number. No attribution means no credit.

Make certain that your README.txt file describes any extra credit attempted.

Tutorial Lab

In preparation for next weeks lessons, complete the following:

  1. Read the assigned reading in the textbook
  2. Complete the Tutorial Exercises in CodeLab 9 before the specified due date.

    Refer to the assigned reading for the next lesson to help you understand the problems. Also, you can use the online lecture notes for more information as the notes become available. You can look at solutions if you miss your first few attempts and are stuck by clicking the "Solution" tab.

Grading Criteria

The instructor will evaluate your assignment using the following criteria. Thus you should check your assignment against these criteria to maximize your score.

Each criteria represents a specific achievement of your assignment and has a scoring guide. The scoring guide explains the possible scores you can receive. Some scoring guides have a list of indicators. These indicators are a sign of meeting, or a symptom of not meeting, the specific criterion. Note that a single indicator may not always be reliable or appropriate in a given context. However, as a group, they show the condition of meeting the criterion.

For information on grading policies, including interpretation of scores, see the syllabus.

Lesson Exercises

  • 2: All lesson exercises attempted and turned in
  • 1: Some lesson exercises completed and turned in
  • 0: No lesson exercises completed or turned in

Class Functionality (x2)

  • 7: Demonstrates mastery of the assignment.
    • Applies concepts from the lessons appropriately
    • Meets all specifications with particularly elegant solutions
    • Runs to completion with no abnormal error conditions
    • Generates correctly formatted output
  • 6: Has all the functionality expected of the assignment with mostly correct formatting.
    • Demonstrates many techniques from the lesson
    • Attempts to meet all specifications
    • Generates correctly formatted output given correct input
    • May have one minor formatting error
  • 5: Has most of the functionality and format expected of the assignment
    • Demonstrates many techniques from the lesson
    • Attempts to meet all specifications
    • Implementation seems more complicated than necessary.
    • May have one or more formatting errors in output
    • May have one minor functional error
  • 4: Has most of the functionality expected of the assignment
    • Demonstrates some techniques from the lesson
    • Attempts to meet all but one of the specifications
    • Implementation seems excessively complicated.
    • May have many formatting errors in output
    • May have 2-3 minor functional errors
  • 3: Has some of the functionality expected of the assignment
    • Attempts to meet at least 1/2 of the specifications
    • Demonstrates many techniques from the lessons
    • Implementation seems excessively complicated.
    • May have more than 3 minor functional errors
    • Source code compiles with no errors or warnings
  • 2: Serious functional problems but shows significant effort and understanding
    • Attempts to meet less than 1/2 of the of the specifications
    • Has a major error or many minor errors
    • Implementation seems very convoluted
    • Demonstrates few techniques from the lessons
    • Source code compiles but may have multiple warnings
  • 1: Serious functional problems but shows some effort and understanding.
    • Does not compile but shows an attempt to meet most specifications
    • Implementation seems somewhat complete but has errors
    • Demonstrates some techniques from the lessons
  • 0: Minimal to no work apparent or made in an incorrect way.
    • Not turned in
    • Does not compile with little work apparent
    • Attempts to meet less than 1/2 of the of the specifications
    • Uses techniques not covered in the course so far

Program Style

  • 4: Code is well-documented including:
  • 3: Code has a minor documentation error.
  • 2: Code has some documentation errors or a missing file.
  • 1: Code has many documentation errors or a missing file and some errors.
  • 0: No apparent attempt to follow documentation standards or write documentation comments

CodeLab and Other Tutorial Exercises

Number completed correctly / number exercises * 8 and rounded up to the nearest integer.

README.txt File

  • 2: README.txt file submitted following the instructions
  • 1: README.txt file submitted but some information was missing
  • 0: No README.txt file submitted

Total possible: 30, plus extra credit

Deliverables

Submit your assignment to Canvas, in the assignment folder A9-Getting Classy, following the instructions for submitting homework. Include the following items for grading:

  1. README.txt file
  2. All the exercise files from Lesson 9
  3. hamster.cpp
  4. song.cpp

Your assignment must work as submitted, so submit all the files needed to complete your assignment. Remember to test and double check your files before submitting them. If you make a mistake, you can resubmit up to the deadline. If you resubmit, you must include all your assignment files in the last submission as Canvas hides prior submissions.

Last Updated: April 28 2019 @18:20:22