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Fixes #4368 - Clarify and Fix CWPPropertyHelper Property Change Workflow

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Refactor ChangeProperty method for clarity and flexibility

Updated the `<param>` documentation for `currentValue` to clarify its behavior. Changed the `currentValue` parameter to be passed by reference (`ref`) to allow direct updates to the caller's variable. Made the `onChanging` delegate nullable and added a null check to prevent potential exceptions. Moved the `cancelled` variable inside the null-check block for `onChanging` to simplify logic. Explicitly updated `currentValue` to `finalValue` after the `doWork` action to ensure consistency. These changes improve the method's robustness, flexibility, and clarity.
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Tig
2025-10-29 12:48:38 -06:00
parent 55d1972bd5
commit e264301e3c
1 changed files with 15 additions and 7 deletions
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22
Terminal.Gui/App/CWP/CWPPropertyHelper.cs
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@@ -22,7 +22,10 @@ public static class CWPPropertyHelper
/// The type of the property value, which may be a nullable reference type (e.g., <see cref="string"/>
/// ?).
/// </typeparam>
/// <param name="currentValue">The current property value, which may be null for nullable types.</param>
/// <param name="currentValue">
/// Reference to the current property value, which may be null for nullable types. If the change is not cancelled, this
/// will be set to <paramref name="finalValue"/>.
/// </param>
/// <param name="newValue">The proposed new property value, which may be null for nullable types.</param>
/// <param name="onChanging">The virtual method invoked before the change, returning true to cancel.</param>
/// <param name="changingEvent">The pre-change event raised to allow modification or cancellation.</param>
@@ -52,9 +55,9 @@ public static class CWPPropertyHelper
/// </code>
/// </example>
public static bool ChangeProperty<T> (
T currentValue,
ref T currentValue,
T newValue,
Func<ValueChangingEventArgs<T>, bool> onChanging,
Func<ValueChangingEventArgs<T>, bool>? onChanging,
EventHandler<ValueChangingEventArgs<T>>? changingEvent,
Action<T> doWork,
Action<ValueChangedEventArgs<T>>? onChanged,
@@ -70,13 +73,17 @@ public static class CWPPropertyHelper
}
ValueChangingEventArgs<T> args = new (currentValue, newValue);
bool cancelled = onChanging (args) || args.Handled;
if (cancelled)
if (onChanging is { })
{
finalValue = currentValue;
bool cancelled = onChanging (args) || args.Handled;
return false;
if (cancelled)
{
finalValue = currentValue;
return false;
}
}
changingEvent?.Invoke (null, args);
@@ -100,6 +107,7 @@ public static class CWPPropertyHelper
doWork (finalValue);
ValueChangedEventArgs<T> changedArgs = new (currentValue, finalValue);
currentValue = finalValue;
onChanged?.Invoke (changedArgs);
changedEvent?.Invoke (null, changedArgs);