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@ -19,11 +19,11 @@ Some of the main focuses behind Vide's design choices:
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- Reducing the amount of imports needed for usage by leveraging Luau's syntax
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and semantics.
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- Being completely typecheckable.
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- Flexibility, particularly with integrating other libraries and allowing users
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to use their own patterns.
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- Flexibility with integrating other libraries and allowing users to use their
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own patterns.
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- Independence from instance lifetimes.
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- A powerful reactive system that can surgically update properties as a result
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of state changes.
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- A powerful reactive system that can update specific properties as a result of
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state changes, updates are immediate with no diffing needed.
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## Structure Of A Vide App
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@ -40,3 +40,6 @@ the updating of the Text property anytime the count is changed.
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All observable changes to the user are considered to be side-effects of the
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reactive system.
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You should not update other sources using an effect. Improper usage can lead to
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unecessary updates and infinite loops.
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@ -1,66 +1,95 @@
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# Control Flow
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Vide has specific functions for dealing with sources that store a table value.
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Eventually you will need a way to dynamically create and destroy UI elements
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resulting from state changes. Vide provides functions to help you do this,
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known as *control flow* functions.
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These functions return a new source, which holds the instances to be displayed.
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These sources can be assigned as children, meaning the displayed children
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will update when the input source updates.
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One of these functions is `switch()`, used to conditionally show one of a set of
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components.
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```lua
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local vide = require(vide)
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local source = vide.source
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local switch = vide.switch
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local function ToggleButton(p: {
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Text: string,
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Toggle: (boolean) -> boolean
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})
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return create "TextButton" {
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Size = UDim2.fromOffset(300, 300),
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Text = p.Text,
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Activated = function()
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p.Toggle(not p.Toggle())
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end
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}
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end
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local loggedIn = source(false)
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local function LoginMenu()
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return Frame {
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switch(loggedIn) {
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[true] = function()
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return ToggleButton { Text = "Log out", Toggle = loggedIn }
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end,
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[false] = function()
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return ToggleButton { Text = "Log in", Toggle = loggedIn }
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end
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}
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}
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end
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mount(function() return create "ScreenGui" { LoginMenu {} } end, game.StarterGui)
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```
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Above is an example of using a switch to create a login menu. Each time
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`loggedIn` toggles, the current button will be destroyed, and a new button
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created, which the text to represent the current action, to log in or log out.
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Another control flow function, `indexes()`, is used to create elements from an
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input table.
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Often, you will have a table of values that will be displayed in a similar
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manner. Rather than manually looping over each value to generate a corresponding
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UI element, Vide provides functions `indexes()` and `values()` to do this for
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you.
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`indexes()` maps each *index* in a table to a UI element.
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UI element, `indexes()` can autmatically run a transform function for each
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index and value, generating a UI element.
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```lua
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local names = source { "a", "b", "c" }
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local todoList = {
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"Finish the crash course",
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"Star vide's GitHub"
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}
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local elements = indexes(names, function(name, i)
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local elements = indexes(todoList, function(todo, i)
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return create "TextLabel" {
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Text = function()
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return "Name: " .. name()
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return i .. ": " .. todo()
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end,
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LayoutOrder = i
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}
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end)
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```
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What happens here is the given callback is only ever ran *once* for each index
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in the table. The callback receives two arguments, a *source* containing the
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index's value and then the index itself.
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Anytime the value at a corresponding index changes, the source for that index
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value is updated, causing the UI element depending on it to update too.
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`values()` behaves similarly, except it maps each *value* in a table to a UI
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element.
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```lua
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type Item = {
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Name: string,
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Icon: number
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}
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local items = source({} :: Array<Item>)
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local elements = values(items, function(item, i)
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return create "ImageLabel" {
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Image = "rbxassetid://" .. item.Icon,
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LayoutOrder = i
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mount(function()
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return create "ScreenGui" {
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create "UIListLayout" {}, elements
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}
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end)
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end, game.StarterGui)
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```
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The callback is again only ever ran *once* for each value in the table. The
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callback receives two arguments, a value in the table and then a *source*
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containing the value's corresponding index.
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For each unique index in the passed table, the transform function will be called
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with 1. a source containing the value of the index, 2. the index itself.
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Any time a value in a table changes index, the source for that value is updated,
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causing the UI element position to change.
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When the value at an index is changed, the function is not reran. Instead, the
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given source is updated instead.
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In certain cases `values()` can cause less recalculation and rerenders than
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`indexes()` like when items are re-arranged and shifted within a table.
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`indexes()` is said to map each *index* in a table to a UI element, each index
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has a single corresponding element.
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It is important that each value in a table is unique when using `values()`,
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and for this reason always using `indexes()` if a table contains primitive
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values.
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Both `indexes()` and `values()` return an array of all mapped UI elements.
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An element is only destroyed if the value of an index is set to `nil`.
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