close()

The close() function in Lua’s coroutine module is employed to gracefully terminate a coroutine and release its associated resources. It yields a boolean value, true, if the coroutine has been successfully closed, otherwise it returns false.

Syntax

coroutine.close(coroutine_thread)

• The close() function is used to explicitly release resources associated with a coroutine, making it safe to close coroutines that have finished their execution.
• Attempting to close a running coroutine or a coroutine that has already been closed will result in an error.
• Always check the return values of coroutine.close() to handle potential errors appropriately.

Example 1

This example uses the close() function to terminate a running coroutine.

local function myCoroutine()
    print("Coroutine is running")
    coroutine.yield()
    print("Coroutine has resumed")
end

local co = coroutine.create(myCoroutine)
coroutine.resume(co) -- Start the coroutine
local success, error_message = coroutine.close(co)
print("Closing coroutine:", success, error_message)

The output is:

Coroutine is running
Closing coroutine:   true   nil

Example 2

This example creates a coroutine using coroutine.create(), starts it with coroutine.resume(), and then closes it with coroutine.close().

local function manageCoroutine()
    local co = coroutine.create(function ()
        print("Coroutine is running")
        coroutine.yield()
        print("Coroutine has resumed")
    end)

    coroutine.resume(co) -- Start the coroutine

    local success, error_message = coroutine.close(co)

    if success then
        print("Coroutine closed successfully")
    else
        print("Error while closing coroutine:", error_message)
    end
end

manageCoroutine()

This will output:

Coroutine is running
Coroutine closed successfully