Checking Coroutine Status

Part of the Logic & Flow section of Coddy's Lua journey — lesson 52 of 54.

As you work with coroutines, you'll often need to know what state a coroutine is in. Is it currently running? Is it paused and waiting to be resumed? Has it finished executing?

Lua provides the coroutine.status() function to answer these questions.

The coroutine.status() function takes a coroutine as its argument and returns a string describing its current state. There are three possible states:

"suspended"	The coroutine is paused at a `yield()` and can be resumed
"running"	The coroutine is currently executing
"dead"	The coroutine has finished execution and cannot be resumed again

Here's how you use it:

function task()
    coroutine.yield()
    print("Finishing")
end

local co = coroutine.create(task)
print(coroutine.status(co))  -- "suspended"

coroutine.resume(co)
print(coroutine.status(co))  -- "suspended" (paused at yield)

coroutine.resume(co)
print(coroutine.status(co))  -- "dead" (finished)

Challenge

Easy

Write a function checkCoroutineLifecycle that takes resumeCount and returns a string showing the status of a coroutine at different points in its lifecycle.

Create a coroutine that yields once, then completes. Check and record its status after creation, after the first resume (when it's paused at yield), and after subsequent resumes based on resumeCount.

Logic:

Create a function that yields the string "paused" once, then completes
Wrap this function in a coroutine using coroutine.create()
Check the status immediately after creation using coroutine.status()
Resume the coroutine once and check its status again
Resume the coroutine additional times based on resumeCount - 1 (total resumes = resumeCount)
Check the final status after all resumes
Return a string with all three statuses in the format: initial: [status]\\nafter first resume: [status]\\nfinal: [status]

Parameters:

resumeCount (number): Total number of times to resume the coroutine (minimum 1)

Returns: A string showing the coroutine status at three points in its lifecycle (string). Format: initial: suspended\nafter first resume: suspended\nfinal: dead

Cheat sheet

The coroutine.status() function returns the current state of a coroutine as a string.

Possible states:

"suspended" - The coroutine is paused at a yield() and can be resumed
"running" - The coroutine is currently executing
"dead" - The coroutine has finished execution and cannot be resumed

Usage:

coroutine.status(coroutine_object)

Example:

function task()
    coroutine.yield()
    print("Finishing")
end

local co = coroutine.create(task)
print(coroutine.status(co))  -- "suspended"

coroutine.resume(co)
print(coroutine.status(co))  -- "suspended"

coroutine.resume(co)
print(coroutine.status(co))  -- "dead"

Try it yourself

function checkCoroutineLifecycle(resumeCount)
    -- Write code here
end

Test yourself

This 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 Sheet

4Introduction to Metatables

What is a Metatable?setmetatable & getmetatable The __index Metamethod The __newindex Metamethod The __tostring Metamethod Arithmetic Metamethods Part 1 Arithmetic Metamethods Part 2 Recap - Read-Only Table

7Advanced String Manipulation

string.gsub() for Substitution Intro to String Patterns string.find()string.match()Iterating with string.gmatch()Recap - Log File Parser

2More Table Library Functions

table.concat()table construction & unpack()table.sort()Custom Sorting with Functions Recap - High Score Board

5Project: Text Adventure Engine

Project Setup: The Room Linking Rooms

Handling Invalid Moves

Displaying Exits

8Project: Contact List

Project Setup The Main Loop

Adding a Contact

Listing All Contacts

Searching for a Contact

Deleting a Contact

Handling Invalid Input

3Advanced Function Concepts

Returning Multiple Values Variadic Functions (...)Functions First-Class Values Anonymous Functions What is a Closure?Recap - Simple Event Handler

6Error Handling

The error() Function Protected Calls with pcall()Recap - Safe Division

9Coroutines for Beginners

What is a Coroutine?coroutine create & resume Pausing with coroutine.yield()resume & yieldChecking Coroutine StatusRecap - Number Generator Recap - Vector Math