vide/docs/api/reactivity-core.md

Reactivity API: Core

:::warning Yielding is not allowed in any stable or reactive scope. Strict mode will check for this. :::

root()

Creates and runs a function in a new stable scope.

• Type

  function root<T...>(fn: (() -> ()) -> T...): (() -> (), T...)
  

• Details

  Returns a function to destroy the root scope. Also passes this function as the first argument into its callback.

  All values returned by the callback are also returned following the destructor.

source()

Creates a new source with the given value.

• Type

  function source<T>(value: T): Source<T>
  
  type Source<T> =
      () -> T -- get
      & (T) -> () -- set
  

• Details

  Calling the returned source with no argument will return its stored value, calling with an argument will set a new value.

• Example

  local count = source(0)
  
  count() -- 0
  
  count(count() + 1) -- 1
  

effect()

Runs a side-effect in a new reactive scope on source update.

• Type

  function effect(callback: () -> ())
  

• Details

  Any time a source referenced in the callback is updated, the callback will be reran.

  The callback is ran once immediately.

• Example

  local num = source(1)
  
  effect(function()
      print(num())
  end)
  
  -- prints 1
  
  num(num() + 1)
  
  -- prints 2
  

derive()

Derives a new source in a new reactive scope from existing sources.

• Type

  function derive<T>(source: () -> T): () -> T
  

• Details

  The derived source will have its value recalculated when any source source it derives from is updated.

  Anytime its value is recalculated it is also cached, subsequent calls will retun this cached value until it recalculates again.

  The callback is ran once immediately.

• Example

  local count = source(0)
  local text = derive(function() return `count: {count()}` end)
  
  text() -- "count: 0"
  
  count(1)
  
  text() -- "count: 1"
  

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