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
endDuring 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)
endThis code will print each item name and its quantity. The pairs() function works with any key type, including strings, numbers, or even other tables.
Challenge
EasyWrite 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: 5banana: 3
Cheat sheet
The pairs() function allows you to loop through all key-value pairs in a dictionary-style table:
for key, value in pairs(myTable) do
-- use key and value here
endDuring each iteration, pairs() provides both the key and its corresponding value, allowing you to access both pieces of information simultaneously.
Example with an inventory table:
local inventory = {
sword = 1,
potion = 5,
gold = 150
}
for item, quantity in pairs(inventory) do
print(item .. ": " .. quantity)
endThe pairs() function works with any key type, including strings, numbers, or even other tables.
Try it yourself
function printInventory(inventory)
-- Write code here
end
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Logic & Flow
1Advanced Table Iteration
Iterating with pairs()Iterating with ipairs()pairs() vs. ipairs()Recap - Character Sheet2More Table Library Functions
table.concat()table construction & unpack()table.sort()Custom Sorting with FunctionsRecap - High Score Board