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https://github.com/littensy/charm.git
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c6762a6525
* fix: cancel reconnection when unsubscribing * test: remove print * feat: allow factory to return nil * perf: use `next` iteration
43 lines
1.1 KiB
Text
43 lines
1.1 KiB
Text
local store = require(script.Parent.store)
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local types = require(script.Parent.types)
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type Molecule<T> = types.Molecule<T>
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--[=[
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Subscribes to changes in the given atom or molecule. The callback is
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called with the current state and the previous state immediately after a
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change occurs.
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@param molecule The atom or molecule to subscribe to.
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@param callback The function to call when the state changes.
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@return A function that unsubscribes the callback.
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]=]
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local function subscribe<T>(molecule: Molecule<T>, callback: (state: T, prev: T) -> ()): () -> ()
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local dependencies, state = store.capture(molecule)
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local disconnected = false
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local function listener()
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local prevState = state
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store.disconnect(dependencies, listener)
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dependencies, state = store.capture(molecule)
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if not disconnected then
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store.connect(dependencies, listener)
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end
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if state ~= prevState then
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callback(state, prevState)
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end
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end
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store.connect(dependencies, listener)
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return function()
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if not disconnected then
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disconnected = true
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store.disconnect(dependencies, listener)
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end
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end
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end
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return subscribe
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