Effects

When working with flecs, it can be useful to track changes that happen to them. Effects allow you to do so.

Effects are special functions that are ran in response to flec updates. Think of a flec as a signal, and an effect as a connection.

Usage

To create an effect, call Teisu.effect:

local Teisu = require(game.ReplicatedStorage.Teisu)

local effect = Teisu.effect
local flec = Teisu.flec

local count = flec(0)

effect(function()
    print(`count: {count()}`)
end)

Effects are ran once to collect flecs that are ready to be read...

Luau code

local count = flec(0)

effect(function()
    print(`count: {count()}`)
end)

Output

count: 0

...and then again whenever any flec changes.

Luau code

effect(function()
    print(`count: {count()}`)
end)

count(1)
count(2)

Output

count: 0
count: 1 
count: 2 

If you don't want a flec to be tracked as a dependency, peek is your best friend!

Luau code

local flec = Teisu.flec
local peek = Teisu.peek
local effect = Teisu.effect

local a = flec(0)
local b = flec(0)

effect(function()
    print(`a: {a()}, b: {peek(b)}`) 
end)

a(1)
b(1) 
a(2)

Output

a: 0, b: 0
a: 1, b: 0
(prints nothing) 
a: 2, b: 1

Disposing effects

An effect returns a function that destroys itself. When this function is called, any subsequent changes will not rerun the callback.

local count = flec(0)

local dispose = effect(function()
    print(`count: {count()}`)
end)

-- destroys the effect after 5 seconds
task.wait(5)
dispose()

count(2) --> will not print anything

In situations where you need to disconnect the effect from the inside, use the dispose function.

local count = flec(0)

effect(function(dispose)
    if count() == 1 then
        dispose()
    end
end)

Effects, when used effectively and efficiently, can make state management feel awesome. In the next section, you'll discover Teisu's built in methods to simplify change tracking.