CS 3005: Programming in C++

Menu System

Introduction

We want to have a text based menu system that allows the user to execute commands from a list of commands. Each command will manipulate the data stored in the program.

Assignment

In this assignment, you will add to the ApplicationData class, and create some new classes that support a menu system. You will also build a very simple program to test this menu system.

The commands this program will have are listed in this table.

Command	Prefixable?	Function	Description
`help`	no	`menuUI`	Display help message.
`menu`	no	`menuUI`	Display help message.
`#`	yes	`commentUI`	Skip to end of line (comment).
`comment`	no	`commentUI`	Skip to end of line (comment).
`echo`	no	`echoUI`	Echo back the arguments given.
`quit`	no	`quitUI`	Terminate the program.

Command indicates the command the user types to request the command.
Prefixable? indicates if the command should be searched for as a prefix (the first characters) of the command typed.
Function indicates the function that the command will call when it is executed.
Description indicates the description of the command.

Example Session

$ ./program-menu-test/menu_test 
Choice? # this is a comment, it does nothing.
Choice? #this is a comment, where the command name is a prefix of the command typed.
Choice? comment this is a comment using the command name, not #
Choice? commentthis is a bad comment, because the "comment" command can not be a prefix.
Unknown action 'commentthis'. Use 'help' for a list of valid actions
Choice? echo Hello world!
 Hello world!
Choice? echo "Hello world!"
 "Hello world!"
Choice? echo copies everything after the echo command to the output.
 copies everything after the echo command to the output.
Choice? echo help will show the list of available commands
 help will show the list of available commands
Choice? help
Options are:
  # - Skip to end of line (comment).
  comment - Skip to end of line (comment).
  echo - Echo back the arguments given.
  help - Display help message.
  menu - Display help message.
  quit - Terminate the program.

Choice? echo menu does too
 menu does too
Choice? menu
Options are:
  # - Skip to end of line (comment).
  comment - Skip to end of line (comment).
  echo - Echo back the arguments given.
  help - Display help message.
  menu - Display help message.
  quit - Terminate the program.

Choice? quit

A Note on Comments

See the additional documentation below on script files.

When people write comments with the # command, sometimes they will write with a space after the hash, like this:

# COMMENT HERE

However, sometimes, people write comments without a leading space, like this:

#LAZY COMMENT HERE

When reading a command, our menu system will use white space (spaces, tabs, newlines) as word separators. In the first case, the # symbol is followed by a space, so it will be considered as a command name. We can then let the comment command handle the rest of the input line.

In the second case, the first space comes after #LAZY, so that is the command name. But #LAZY is not in our command list. If we don’t do something about this, the program will say that is an unknown command, then try to read the next word as a command, COMMENT is also not a command, so we get another error message. HERE is also not a command, so we get yet another error message.

So, let’s do something about it. We will tag the # command in our command list as a prefix command of length 1. When we scan to see if a user typed command is in the list of commands, if the first character (because length is 1), matches the command name #, we will consider it a # command. This way #LAZY is considered an alias for the #.

Commands that are not meant to function as prefix commands are will have a prefix length of 0 to indicate that they are not a prefix command.

A Note on Reference Returns

If a function returns a reference (&), the object being referenced must exist after the function ends.

Often, we use reference return types for a method of a class, when the method is returning a data member, or an element of a data member container. For example, we might return a reference to the value in a data member map associated with a key sent as a parameter.

A problem arises if the item the function has been asked to return does not exist. In this case, we still need to return a reference, or the function does not have valid syntax.

We could create a local variable on the stack to return, representing the error case. This is not correct. Remember all stack variables are removed as soon as the function returns. So, the reference would be to an object that no loner exists.

The solution is to create a variable that is locally scoped, but stored in the static section of memory. It will continue to exist after the function returns.

A Note on Clearing to EOL

See class discussion.

A Note on Input Streams

See class discussion.

Programming Requirements

Create `library-application/ActionFunctionData.{h,cpp}`

`ActionFunctionData` Class

This class represents one command, or action, that the user can execute. Think of it as a row in the table of commands listed above.

`public` Typedefs:

typedef void (*ActionFunctionType)(ApplicationData&); Creates the ActionFunctionType.

Data Members:

The following data members should be private or protected. public data members are not allowed.

std::string name for the command. This is the command the user types to execute it.
ActionFunctionType the function that is called when the user types the command.
std::string the command description given to the user when they ask for help.
int the length of the prefix. 0 if the command is not allowed to be a prefix.

`public` Methods:

ActionFunctionData(); Default constructor, initializes all data members to "" and 0 as appropriate.
ActionFunctionData(const std::string& name, const ActionFunctionType& function, const std::string& description); Initializes all data members to the given arguments, expect prefix_length which is set to 0.
ActionFunctionData(const std::string& name, const ActionFunctionType& function, const std::string& description, const int prefix_length); Initializes all data members to the given argument.
const std::string& getName() const; Returns the data member.
ActionFunctionType getFunction() const; Returns the data member.
const std::string& getDescription() const; Returns the data member.
int getPrefixLength() const; Returns the data member.
void setName(const std::string& name); Sets the data member.
void setFunction(ActionFunctionType function); Sets the data member.
void setDescription(const std::string& description); Sets the data member.
void setPrefixLength(const int length); Sets the data member.

Update `library-application/Makefile`

Add ActionFunctionData.{h,cpp} in the appropriate places to add them to the library and install the header file. Unless, of course, you have adopted the updated Makefile setup we built in class.

Create `library-application/MenuData.{h,cpp}`

`MenuData` Class

This class represents all of the commands the user can execute. Think of it as all of the rows in the table of commands listed above.

Data Members:

The following data members should be private or protected. public data members are not allowed.

std::map<std::string, ActionFunctionData> A map of command names to the action function data for the command.

`protected` Methods:

These methods must be protected, not public, and not private.

bool actionExistsAux(const std::string& name) const; If name is a key in the map, return true. Otherwise return false.
const std::string actionPrefix(const std::string& name) const; If the key of a command is the first prefix_length of name, return the key. Otherwise, return the empty string.

`public` Methods:

MenuData(); Default constructor. Does not need to initialize any data members. The std::map default constructor will automatically build an empty map.
void addAction(const ActionFunctionData& function); If the action already exists, do nothing. If the action does not exist, add it to the map.
bool actionExists(const std::string& name) const; If name is a key in the map, or if name’s prefix is a key in the map, return true. Otherwise return false. You should be using the protected methods to do most of the work here.
const ActionFunctionData& getAction(const std::string& name); If name is an action, return the ActionFunctionData associated with it. Otherwise, return a static default constructed ActionFunctionData object.
void printActionHelp(std::ostream& out) const; Send the help message to out. Use the form shown in the example session above.

Update `library-application/Makefile`

Add MenuData.{h,cpp} in the appropriate places to add them to the library and install the header file. Unless, of course, you have adopted the updated Makefile setup we built in class.

Update `library-application/ApplicationData.{h,cpp}`

We will update the ApplicationData class to support a text menu based application.

`ApplicationData` Class

Data Members:

These additional data members should be in the private or protected section of the class. No public data members are allowed.

bool a variable to track whether the application is done or not. Initialized to false in the constructor.
MenuData a collection of the commands supported by the application. The default constructor for MenuData will be called automatically without any new code in the constructor.

`public` Methods:

Constructor: Initializes the new data members.
void addAction(const ActionFunctionData& action); Adds action to the MenuData data member.
void setDone(bool done); Sets the new bool data member to the value of done.
void printActionHelp(); Causes the MenuData data member’s printActionHelp method to be called. Uses the ApplicationData data member for output stream.
void clearToEOL(); Reads from the ApplicationData data member for input stream until the end of line (EOL) is found. The EOL can happen in one of two ways. 1) A new line character is read. 2) The end of the stream is reached. The data read from the stream is discarded. The whole point is to advance the input.
void takeAction(const std::string& choice); If choice is the name of an action in the MenuData data member, call the ActionFunctionType associated with the action. Otherwise, print an error message and clear to end of line. The error message format can be seen in the example session above.
void mainLoop(); While the input stream is good() and the data member tracking done is false, read the user’s “Choice? ” from the input stream and take the action indicated by the choice.

Create `library-commands/menu_test_aux.{h,cpp}`

Functions:

void menuUI(ApplicationData& app_data); Uses app_data to display the action help and clears to EOL.
void commentUI(ApplicationData& app_data); Clears the input to the EOL.
void echoUI(ApplicationData& app_data); Collect all of the characters in the input stream up to the EOL. Send them to the output stream, followed by a newline character.
void quitUI(ApplicationData& app_data); Sets the app_data’s done to be true.
int register_menu_test_commands(ApplicationData& app_data); Adds all of the actions in the table above to the app_data.
int menu_test(ApplicationData& app_data); Uses register_menu_test_commands to create all of the commands, then calls app_data.mainLoop(). Returns 0.

Update `library-commands/Makefile`

Add menu_test_aux.{h,cpp} in the appropriate places to add them to the library and install the header file. Unless, of course, you have adopted the updated Makefile setup we built in class.

Create `program-menu-test/menu_test.cpp`

Functions:

int main(); Entry point to the menu test program. Should create an ApplicationData and pass it to the menu_test function found in menu_test_aux and return the result of that function call.

Create `program-menu-test/Makefile`

This file must contain rules such that any of the following commands will build the menu_test program:

make
make all
make menu_test

Create `program-menu-test/.gitignore`

The file needs to store one line of text:

menu_test

This will prevent the executable program from being committed to the repository. It is a derived file.

Update `Makefile`

Update the project-level Makefile so that make and make all in the project directory will call make in the program-menu-test directory.
If necessary, make sure the order of make commands is correct to build prerequisite libraries in the correct order.

Additional Documentation

Scripting input

Grading Instructions

To receive credit for this assignment:

your code must be pushed to your repository for this class on GitHub
all unit tests must pass
all acceptance tests must pass
all programs must build, run, and execute as described in the assignment descriptions.

Extra Challenges (Not Required)

TBA

Last Updated 02/28/2025

CS 3005: Programming in C++

Menu System

Introduction

Assignment

Example Session

A Note on Comments

A Note on Reference Returns

A Note on Clearing to EOL

A Note on Input Streams

Programming Requirements

Create library-application/ActionFunctionData.{h,cpp}

ActionFunctionData Class

public Typedefs:

Data Members:

public Methods:

Update library-application/Makefile

Create library-application/MenuData.{h,cpp}

MenuData Class

Data Members:

protected Methods:

public Methods:

Update library-application/Makefile

Update library-application/ApplicationData.{h,cpp}

ApplicationData Class

Data Members:

public Methods:

Create library-commands/menu_test_aux.{h,cpp}

Functions:

Update library-commands/Makefile

Create program-menu-test/menu_test.cpp

Functions:

Create program-menu-test/Makefile

Create program-menu-test/.gitignore

Update Makefile

Additional Documentation

Grading Instructions

Extra Challenges (Not Required)

Create `library-application/ActionFunctionData.{h,cpp}`

`ActionFunctionData` Class

`public` Typedefs:

`public` Methods:

Update `library-application/Makefile`

Create `library-application/MenuData.{h,cpp}`

`MenuData` Class

`protected` Methods:

`public` Methods:

Update `library-application/Makefile`

Update `library-application/ApplicationData.{h,cpp}`

`ApplicationData` Class

`public` Methods:

Create `library-commands/menu_test_aux.{h,cpp}`

Update `library-commands/Makefile`

Create `program-menu-test/menu_test.cpp`

Create `program-menu-test/Makefile`

Create `program-menu-test/.gitignore`

Update `Makefile`