Recap - Score Tracker

Part of the Object Oriented Programming section of Coddy's Lua journey. Lesson 69 of 70.

Challenge

Easy

Let's build a score tracking system for a gaming leaderboard! You'll create two classes that work together: one representing individual score entries, and another managing the leaderboard with sorting capabilities powered by operator overloading.

You'll organize your code across three files:

ScoreEntry.lua: Create a ScoreEntry class that represents a single player's score. Each entry has a playerName and a score. Include a :getInfo() method that returns a string in the format "{playerName}: {score} points". The key feature here is the __lt metamethod: a < b should be true when a's score is lower than b's, the same way < works on numbers.
Leaderboard.lua: Build a Leaderboard class that manages a collection of score entries. Your leaderboard needs:
- :addEntry(entry): adds a ScoreEntry to the internal list
- :sort(): sorts entries from highest to lowest score using table.sort. On its own, table.sort puts the smallest first, so pass it a comparison that reverses the order: function(a, b) return b < a end. That comparison still uses your __lt.
- :display(): prints the info for each entry, one per line
main.lua: Bring everything together! Create a Leaderboard, add score entries based on the inputs you receive, sort the leaderboard, and display the results.

Comparing two entries with < calls your __lt metamethod, so table.sort can order ScoreEntry objects. Keep __lt meaning "less than" and reverse the order in the sort call: if __lt meant "greater than", every < on two entries anywhere in the program would read backwards.

You will receive six inputs representing three players:

First player's name
First player's score (a number)
Second player's name
Second player's score (a number)
Third player's name
Third player's score (a number)

In your main file, create a leaderboard, add all three entries, call :sort(), then call :display() to show the sorted results.

For example, if the inputs are Alice, 1500, Bob, 2300, Charlie, and 1800, the output should be:

Bob: 2300 points
Charlie: 1800 points
Alice: 1500 points

If the inputs are Zara, 500, Max, 750, Luna, and 600, the output should be:

Max: 750 points
Luna: 600 points
Zara: 500 points

Try it yourself

-- Main file: Bring everything together
local ScoreEntry = require('ScoreEntry')
local Leaderboard = require('Leaderboard')

-- Read inputs for three players
local name1 = io.read()
local score1 = tonumber(io.read())
local name2 = io.read()
local score2 = tonumber(io.read())
local name3 = io.read()
local score3 = tonumber(io.read())

-- TODO: Create a new Leaderboard

-- TODO: Create ScoreEntry objects for each player

-- TODO: Add all three entries to the leaderboard

-- TODO: Sort the leaderboard

-- TODO: Display the sorted results