Requirements

When the application starts, it will automatically populate the "Student Roster" list box, but nothing else works. Your task is to complete the following:

Record Attendance Button

When the application starts, the "Record Attendance" button is disabled, as seen at the beginning of the video.

The button should only be enabled $($and therefore clickable$)$ when the text in "Student Email" exactly matches an email address from the roster. That is if the text in "Student Email" is not the same as one of the roster items, the button should stay disabled. This check should be performed using the ON$\_$CHANGE event of the "Student Email" input.

Clicking the button should record the attendance of the student whose email is written in the input, and update the counter.

You are free to make other UI$/$UX $($User Interface$/$User Experience$)$ enhancements, if you wish.

Student Roster Listbox Filtering

A required UX enhancement is for the "Student Roster" list box to dynamically update its contents as the user types in the "Student Email" input.

The "Student Roster" list box should contain only those emails that begin with the same sequence of characters as what is typed in the "Student Email" input.

Example

Student Roster contents:

bryce@ucmerced.edu

alice@ucmerced.edu

bill@ucmerced.edu

jerry@ucmerced.edu

brian@ucmerced.edu

Case $1$

Student Email contents: $"$b$",$ then Student Roster is:

bryce@ucmerced.edu

bill@ucmerced.edu

brian@ucmerced.edu

because these are the only ones that start with $"$b$".$

Case $2$

Student Email contents: $"$br$",$ then Student Roster is:

bryce@ucmerced.edu

brian@ucmerced.edu

because these are the only ones that start with $"$br$".$

Case $3$

Student Email input box in empty, then Student Roster is:

bryce@ucmerced.edu

alice@ucmerced.edu

bill@ucmerced.edu

jerry@ucmerced.edu

brian@ucmerced.edu

because there is no string to filter by$,$ so we include everything.

Record Attendance Duplication

As described above, once a matching email is found in the Student Roster, the "Record Attendance" button should be activated. The application must prevent the user from recording attendance for the same student more than once.

Hints :This program uses a container called a vector $($line $20).$ A vector is a special type of variable in C$++$ that can be used to store more than $1$ value. The particular vector on line $20$ is a vector of string, meaning that it can store multiple string values, unlike a regular string variable that can hold only one.

A vector of string is similar to a ListBox component in Bobcat UI$,$ as they both store collections of string values. Consequently, the contents of a ListBox can be derived from a vector. Line $51$ in the code sets the values of the vector, and the populateRosterList function on lines $40-44,$ uses the contents of the vector to populate the ListBox.

A ListBox can be cleared by calling a $->$clear$()$ function on it$.$ If we then have a vector of string values, we can use code similar to the populateRosterList function to fill up the ListBox with content.

This is useful for filtering applications. Suppose we have a vector of strings, and it has hundreds of values. We can create another vector and make it start out empty. The C$++$ code for that is:

$$std::vector filteredList;

This creates an empty vector called filteredList. We can add values to this empty vector by saying:

$$filteredList$.$push$\_$back$(...)$;

where the $...$ is some string value.

If we had a filteredList like that, we could make the contents of the "Student Roster" list box to be the filteredList, not the roster vector.

To create such a list, what we would need to do is go through the roster vector, and for every item inside it$,$ check if it starts with the text from the "Student Email" input box. If it does, then add it to the filteredList.

The way to check if a word starts with a given sequence of characters is to use the startsWith function, on lines $30-37.$

This is a function that takes in two string values big and small, and checks if big starts with the sequence of characters written in small.

Examples

$$startsWith$("$brian$","$br$")$; $//=>$ true$$startsWith$("$hello$","$br$")$; $//=>$ false$$startsWith$("$hello$","$he$")$; $//=>$ true$$startsWith$("$hello$","$el$")$; $//=>$ false

std::vectorstd::string roster;

$//$ components

ListBox$*$ rosterList;

ListBox$*$ attendanceRecordList;

Input$*$ emailInput;

ReturnButton$*$ recordAttendanceButton;

TextBox$*$ attendanceCountText;

$//$ check if string string $($big$)$ starts with a substring $($small$)$

bool startsWith$($std::string big, std::string small$)\{$

for $($int i $=0$; i $$ small.length$()$; i$++)\{$

if $($toupper$($c: big$[$i$])!=$ toupper$($c: small$[$i$]))\{$

return false;

$\}$

return true;

$\}$

$//$ populate rosterList using roster vector data

void populateRosterList$()$

for $($int i $=0$; i $$ roster.size$()$; i$++)\{$

rosterList$->$add$($text: roster$[$i$])$;

$\}$

public

Application$()$

theme$()$;

$//$ initializing state variables

attendanceCount $=0$;

$//$ initializing components

window $=$ new Window$($x:$100,$ y:$100,$ w:$400,$ h:$400,$ title: "Attendance Recorder

Attendance Recorder

Studen