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Guard against inner component null messages #1080

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Guard against inner component null messages #1080

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1992e29
Guard against inner component null messages
edgarfgp May 2, 2024
080c33c
format code
edgarfgp May 2, 2024
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9 changes: 6 additions & 3 deletions src/Fabulous/Runner.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ open System.Collections.Concurrent
// Runner is created for the component itself. No point in reusing a runner for another component

/// Create a new Runner handling the update loop for the component
type Runner<'arg, 'model, 'msg>(getState: unit -> 'model, setState: 'model -> unit, program: Program<'arg, 'model, 'msg>) =
type Runner<'arg, 'model, 'msg when 'msg: null>(getState: unit -> 'model, setState: 'model -> unit, program: Program<'arg, 'model, 'msg>) =
let mutable _activeSubs = Sub.Internal.empty
let mutable _reentering = false
let mutable _stopped = false
Expand All @@ -20,11 +20,14 @@ type Runner<'arg, 'model, 'msg>(getState: unit -> 'model, setState: 'model -> un
raise ex

let processMsgs dispatch msg =
let mutable lastMsg = ValueSome msg
// In cases where you have a Component() which itself is in a Component(program) and a side effect happens in the inner component, the outer component will dispatch a message that is null
// So here we need make sure that we don't process null messages `ValueSome null`
let mutable lastMsg = ValueOption.ofObj(msg)

while not _stopped && lastMsg.IsSome do
let model = getState()
let newModel, cmd = program.Update(lastMsg.Value, model)

let newModel, cmd = program.Update(unbox lastMsg.Value, model)
let subs = program.Subscribe(newModel)

setState newModel
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