Iterating with pairs()

Part of the Logic & Flow section of Coddy's Lua journey. Lesson 1 of 54.

When working with dictionary-style tables in Lua, you often need to access every key-value pair stored inside. The pairs() function makes this possible by allowing you to loop through all entries in a table, regardless of what type the keys are.The syntax for using pairs() in a for loop looks like this:

for key, value in pairs(myTable) do
    -- use key and value here
end

During each iteration of the loop, pairs() provides both the key and its corresponding value. This means you can access and work with both pieces of information at the same time.Here's a practical example with a player's inventory:

local inventory = {
    sword = 1,
    potion = 5,
    gold = 150
}

for item, quantity in pairs(inventory) do
    print(item .. ": " .. quantity)
end

This code will print each item name and its quantity. The pairs() function works with any key type, including strings, numbers, or even other tables.For the challenge: building a stringThe challenge below asks you to return every entry as one string, so here is a reminder of two string tools from Fundamentals. You join strings with the concatenation operator, which is two dots (..). For example, "Hello" .. " " .. "World" results in "Hello World".If you need to format text across multiple lines, you can use the newline escape character, "\n". When Lua encounters "\n" inside a string, it treats it as a command to move to the next line.For example, print("Line 1\nLine 2") will output:

Line 1
Line 2

Challenge

Easy

Write a function printInventory that takes an inventory table and returns a formatted string listing all items and their quantities.

Use pairs() to iterate through the inventory table and build a string where each line shows an item name followed by its quantity in the format item: quantity. Each item should be on a separate line.

To place each item on its own line, use the newline character "\n" between entries. For example, "apple: 5\nbanana: 3" will display as two separate lines. Be careful not to add a leading "\n" before the first item: only add it between items.

Parameters:

inventory (table): A dictionary-style table where keys are item names (strings) and values are quantities (numbers)

Returns: A string with each item and quantity on a separate line, separated by "\n". Example output for {apple=5, banana=3}:
apple: 5
banana: 3

Try it yourself

function printInventory(inventory)
    -- To format the output, you can concatenate strings using the '..' operator.
    -- To add a new line, use the special character '\n'.
    -- You might need a way to track if you are adding the first item or a subsequent one
    -- to decide whether to add a newline before the item.
    
    -- Write code here
end