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Create a useStateLazy method which takes a callback #277

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merged 2 commits into from
Mar 2, 2023
Merged

Create a useStateLazy method which takes a callback #277

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915bc4e
Create a useStateLazy method which takes a callback to get the initia…
marklam Mar 1, 2023
f75b14d
Update src/Avalonia.FuncUI/Components/Context/Context.fs
marklam Mar 2, 2023
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29 changes: 29 additions & 0 deletions src/Avalonia.FuncUI/Components/Context/Context.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,25 @@ type IComponentContext =
/// <param name="renderOnChange">re-render component on change (default: true).</param>
abstract useState<'value> : initialValue: 'value * ?renderOnChange: bool -> IWritable<'value>

/// <summary>
/// Attaches a value from a function to the component context.
/// <example>
/// <code>
/// Component (fun ctx ->
/// (* expensive operation that should only happen once on initialisation *)
/// let count = ctx.useStateLazy (fun () -> Math.Sqrt(42))
/// ..
/// // id will have the same value during the whole component lifetime. (unless changed via 'id.Set ..')
/// let id = ctx.useState ((fun () -> Guid.NewGuid()), renderOnChange=false)
/// ..
/// )
/// </code>
/// </example>
/// </summary>
/// <param name="buildInitialValue">function will be called once during the component lifetime.</param>
/// <param name="renderOnChange">re-render component on change (default: true).</param>
abstract useStateLazy<'value> : buildInitialValue: (unit -> 'value) * ?renderOnChange: bool -> IWritable<'value>

/// <summary>
/// Attaches a passed <c>IWritable&lt;'value&gt;</c> value to the component context.
/// <example>
Expand Down Expand Up @@ -317,6 +336,16 @@ type Context (componentControl: Avalonia.Controls.Border) =
)
) :?> IWritable<'value>

member this.useStateLazy(buildInitialValue: unit -> 'value, ?renderOnChange: bool) =
this.useStateHook<'value>(
StateHook.Create (
identity = callingIndex,
state = StateHookValue.Lazy (fun _ -> new State<'value>(buildInitialValue()) :> IAnyReadable),
renderOnChange = defaultArg renderOnChange true
)
) :?> IWritable<'value>


member this.control = componentControl

interface IDisposable with
Expand Down