Getting Started

Install

Installing Crystal is very simple. Just drop the module into ReplicatedStorage.

Roblox Studio workflow:

• Get Crystal from the Release.
• Place Crystal directly within ReplicatedStorage.

Rojo/Wally workflow:

• Add Crystal to your wally.toml dependency list (e.g. crystal = "animalstudioofficial/crystal@^0.8.0"")

• Require Crystal like any other module grabbed from Wally

  Wally

  Not familiar with Wally? Wally is a package manager (like NPM) for the Roblox ecosystem. To get started, check out the Wally repository.

Basic Usage

The core usage of Crystal is the same from the server and the client. The general pattern is to create a single script on the server and a single script on the client. These scripts will load Crystal, create services/controllers, and then start Crystal.

The most basic usage would look as such:

local Crystal = require(game:GetService("ReplicatedStorage").Packages.Crystal)

Crystal.Start():catch(warn)
-- Crystal.Start() returns a Promise, so we are catching any errors and feeding it to the built-in 'warn' function
-- You could also chain 'await()' to the end to yield until the whole sequence is completed:
--    Crystal.Start():catch(warn):await()

That would be the necessary code on both the server and the client. However, nothing interesting is going to happen. Let's dive into some more examples.

A Simple Service

A service is simply a structure that serves some specific purpose. For instance, a game might have a MoneyService, which manages in-game currency for players. Let's look at a simple example:

local Crystal = require(game:GetService("ReplicatedStorage").Packages.Crystal)

-- Create the service:
local MoneyService = Crystal.CreateService {
    Name = "MoneyService",
}

-- Add some methods to the service:

function MoneyService:GetMoney(player)
    -- Do some sort of data fetch
    local money = someDataStore:GetAsync("money")
    return money
end

function MoneyService:GiveMoney(player, amount)
    -- Do some sort of data fetch
    local money = self:GetMoney(player)
    money += amount
    someDataStore:SetAsync("money", money)
end

Crystal.Start():catch(warn)

note

It's better practice to put services and controllers within their own ModuleScript and then require them from your main script. For the sake of simplicity, they are all in one script for these examples.

Now we have a little MoneyService that can get and give money to a player. However, only the server can use this at the moment. What if we want clients to fetch how much money they have? To do this, we have to create some client-side code to consume our service. We could create a controller, but it's not necessary for this example.

First, we need to expose a method to the client. We can do this by writing methods on the service's Client table:

-- Money service on the server
...
function MoneyService.Client:GetMoney(player)
    -- We already wrote this method, so we can just call the other one.
    -- 'self.Server' will reference back to the root MoneyService.
    return self.Server:GetMoney(player)
end
...

We can write client-side code to fetch money from the service:

-- Client-side code
local Crystal = require(game:GetService("ReplicatedStorage").Packages.Crystal)
Crystal.Start():catch(warn):await()

local MoneyService = Crystal.GetService("MoneyService")

MoneyService:GetMoney():andThen(function(money)
    print(money)
end)

-- Don't want to use promises? When you start Crystal on the client,
-- set the ServicePromises option to false:

Turn Off Promises

Don't want to use promises when the client calls a service method? Set the ServicePromises option to false when you start Crystal on the client:

Crystal.Start({ServicePromises = false}):catch(warn):await()

local MoneyService = Crystal.GetService("MoneyService")

local money = MoneyService:GetMoney()

Under the hood, Crystal is creating a RemoteFunction bound to the service's GetMoney method. Crystal keeps RemoteFunctions and RemoteEvents out of the way so that developers can focus on writing code and not building communication infrastructure.

Check out the Services documentation for more info on services.