#Values

event declares a named value and binds a callback to it.

local Interface = Scope:Capture({
    ClassName = "TextLabel",
    mount(PlayerGui),

    event("Count", 0, function(self, _, Value)
        self.Text = `Clicks: {Value}`
    end),
})

Interface:Mount()

Interface.Count(5)   -- label now reads "Clicks: 5"

The name becomes a field on the Vision. Call it with nothing to read, with a value to write. A write returns the value, so it composes:

local Next = Interface.Count(Interface.Count() + 1)

#Staged writes coalesce

Before mounting, a write only stores:

Interface.Count(1)
Interface.Count(2)
Interface.Count(3)
-- nothing has run

Interface:Mount()
-- the callback runs once, with 3

#Unchanged writes are skipped

After mounting, writing the value it already holds does nothing at all:

Interface.Mode("active")   -- callbacks run
Interface.Mode("active")   -- skipped

Which means you can write freely from a loop or a network handler without checking first.

#One value, many instances

This is where it gets useful. merge binds another callback to a value declared elsewhere:

{
    ClassName = "Frame",
    mount(PlayerGui),

    {
        ClassName = "TextLabel",
        Name = "Percent",

        event("Fill", 0.2, function(self, _, Value)
            self.Text = string.format("%.0f%%", Value * 100)
        end),
    },

    {
        ClassName = "Frame",
        Name = "Bar",

        merge("Fill", function(self, _, Value)
            self.Size = UDim2.fromScale(Value, 1)
        end),
    },
}

One write updates both, and each callback gets its own self:

Interface.Fill(0.75)

Declaring the same name with event twice does the same thing as merge - the second declaration adds a binding rather than replacing the value. The first InitialValue wins.

#Next

Lifecycle - running code at the right time.