Vision

#Migrating

Moving a tree over from another library. Pick the one you came from:

The per-library pages are lookup tables. This page is the part that is the same whichever one you are leaving.

#Three shifts

Nothing exists until you mount. Capture reads your table and returns a handle without creating a single instance. Writes made before Mount only store, so the tree appears already correct instead of appearing wrong and being corrected. Every other library on this list builds as it evaluates.

Nothing re-renders. There is no virtual tree, no diff, and no reconciler. A value write calls the callbacks bound to that value, and those callbacks assign properties. A component function runs once, when you build the declaration, not again on every change.

A scope owns the instances. Scope:Release() destroys what the scope created. This is closer to Fusion's scopes than to Roact or Vide, both of which leave the instances to you.

#The shared translation

you had Vision
a component a function returning a declaration table
state event("Name", Initial, Callback)
derived state derive("Name", Compute)
reading state Interface.Name()
writing state Interface.Name(Value)
an event handler prop a plain key, Activated = function(self, vision) end
a property listener PropertyChanged = { Text = function(self, vision, Value) end }
an attribute listener AttributeChanged = { Role = function(self, vision, Value) end }
render or mount Scope:Capture(Declaration) then Interface:Mount()
unmount Interface:Cleanup(), or Scope:Release() for the lot
a ref Interface:Open(), or ready(function(self) end)
an on-mount effect ready
that effect's teardown the third argument ready hands you
a per-node teardown cleanup(function(self, vision) end)
a portal mount(Target) on the node, pointing anywhere

Every callback is called as (instance, vision, ...). The instance comes first, the vision that built it second, and whatever the callback carries after that. See declarations.

#What Vision does not have

Worth knowing before you start, because there is no drop-in for these.

#What Vision has that you may not have had