vide/docs/api/reactivity-utility.md

Reactivity API: Utility

cleanup()

Runs a callback anytime a function scope is re-ran.

• Type

  function cleanup(callback: () -> ())
  

• Details

  The primary purpose of this function is to provide a means of cleaning up side effects caused by source updates and watch() updates.

  The stack is inspected to find the function that calls cleanup(). The callback passed is called anytime the caller is re-ran, and when the caller finally garbage collects.

  ::: warning Only one cleanup() call is allowed per function scope. :::

• Example

  local data = source(1)
  
  watch(function()
      local label = create "TextLabel" { Text = data() }
  
      cleanup(function()
          label:Destroy()
      end)
  end)
  

  local data = source(1)
  
  derive(function()
      local label = create "TextLabel" { Text = data() }
  
      cleanup(function()
          label:Destroy()
      end)
  
      return label
  end)
  

untrack()

Gets the value of a source without reactively tracking it.

• Type

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

• Details

  Updates made to a source passed to untrack() will not cause updates to anything depending on that source.

• Example

  local a = source(0)
  local b = source(0)
  
  local sum = derive(function()
      return a() + untrack(b)
  end)
  
  print(sum()) -- 0
  b(1)
  print(sum()) -- 0
  a(1)
  print(sum()) -- 2