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authorE.Z. Hart <hartez@users.noreply.github.com>2016-12-01 14:15:17 -0700
committerStephane Delcroix <stephane@delcroix.org>2016-12-01 23:08:30 +0100
commit6217c08c127b2b8846d61c5221e088161035bbee (patch)
treea7fddf1e09c31f048f9090dfdef5fc4933c392c7
parent39dabc3957c985171350865fd94d9e758481dcda (diff)
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Don't run Command CanExecute on incorrect inherited binding context type (#572)
* Allow Command CanExecute to recover when run on inherited bindingcontext * Make exception handler more generic * Checking types in Command delegates to avoid exception in the first place * Adding type chekc to other Command constructor * Use nameof for ArgumentNullExceptions * Add unit tests for null parameters, handle value types and Nullable<T>
-rw-r--r--Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla47971.cs109
-rw-r--r--Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems3
-rw-r--r--Xamarin.Forms.Core.UnitTests/CommandTests.cs100
-rw-r--r--Xamarin.Forms.Core/Command.cs62
4 files changed, 259 insertions, 15 deletions
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla47971.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla47971.cs
new file mode 100644
index 00000000..351028d4
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla47971.cs
@@ -0,0 +1,109 @@
+´╗┐using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+ [Preserve(AllMembers = true)]
+ [Issue(IssueTracker.Bugzilla, 47971, "UWP doesn't display list items when binding a CommandParameter to BindingContext in a DataTemplate and including a CanExecute method", PlatformAffected.WinRT)]
+ public class Bugzilla47971 : TestContentPage
+ {
+ protected override void Init()
+ {
+ var viewModel = new _47971ViewModel();
+
+ var lv = new ListView { BindingContext = viewModel };
+
+ lv.SetBinding(ListView.ItemsSourceProperty, new Binding("Models"));
+ lv.SetBinding(ListView.SelectedItemProperty, new Binding("SelectedModel"));
+
+ lv.ItemTemplate = new DataTemplate(() =>
+ {
+ var tc = new TextCell();
+
+ tc.SetBinding(TextCell.TextProperty, new Binding("Name"));
+ tc.SetBinding(TextCell.CommandParameterProperty, new Binding("."));
+ tc.SetBinding(TextCell.CommandProperty, new Binding("BindingContext.ModelSelectedCommand", source: lv));
+
+ return tc;
+ });
+
+ var layout = new StackLayout { Spacing = 10 };
+ var instructions = new Label {Text = "The ListView below should display three items (Item1, Item2, and Item3). If it does not, this test has failed." };
+
+ layout.Children.Add(instructions);
+ layout.Children.Add(lv);
+
+ Content = layout;
+ }
+
+ [Preserve(AllMembers = true)]
+ internal class _47971ViewModel : INotifyPropertyChanged
+ {
+ _47971ItemModel _selectedModel;
+ Command<_47971ItemModel> _modelSelectedCommand;
+ ObservableCollection<_47971ItemModel> _models;
+
+ public ObservableCollection<_47971ItemModel> Models
+ {
+ get { return _models; }
+ set
+ {
+ _models = value;
+ OnPropertyChanged();
+ }
+ }
+
+ public _47971ItemModel SelectedModel
+ {
+ get { return _selectedModel; }
+ set
+ {
+ _selectedModel = value;
+ OnPropertyChanged();
+ }
+ }
+
+ public Command<_47971ItemModel> ModelSelectedCommand => _modelSelectedCommand ??
+ (_modelSelectedCommand = new Command<_47971ItemModel>(ModelSelectedCommandExecute, CanExecute));
+
+ bool CanExecute(_47971ItemModel itemModel)
+ {
+ return true;
+ }
+
+ void ModelSelectedCommandExecute(_47971ItemModel model)
+ {
+ System.Diagnostics.Debug.WriteLine(model.Name);
+ }
+
+ public _47971ViewModel()
+ {
+ _models = new ObservableCollection<_47971ItemModel>(
+ new List<_47971ItemModel>()
+ {
+ new _47971ItemModel() { Name = "Item 1"},
+ new _47971ItemModel() { Name = "Item 2"},
+ new _47971ItemModel() { Name = "Item 3"}
+ });
+ }
+
+ public event PropertyChangedEventHandler PropertyChanged;
+
+ protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
+ {
+ PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+ }
+ }
+
+ [Preserve(AllMembers = true)]
+ internal class _47971ItemModel
+ {
+ public string Name { get; set; }
+ }
+ }
+} \ No newline at end of file
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
index 92fb8725..5979f04a 100644
--- a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
@@ -126,6 +126,7 @@
<Compile Include="$(MSBuildThisFileDirectory)Bugzilla43516.cs" />
<Compile Include="$(MSBuildThisFileDirectory)Bugzilla44166.cs" />
<Compile Include="$(MSBuildThisFileDirectory)Bugzilla44338.cs" />
+ <Compile Include="$(MSBuildThisFileDirectory)Bugzilla47971.cs" />
<Compile Include="$(MSBuildThisFileDirectory)CarouselAsync.cs" />
<Compile Include="$(MSBuildThisFileDirectory)Bugzilla34561.cs" />
<Compile Include="$(MSBuildThisFileDirectory)Bugzilla34727.cs" />
@@ -583,4 +584,4 @@
<Generator>MSBuild:UpdateDesignTimeXaml</Generator>
</EmbeddedResource>
</ItemGroup>
-</Project> \ No newline at end of file
+</Project>
diff --git a/Xamarin.Forms.Core.UnitTests/CommandTests.cs b/Xamarin.Forms.Core.UnitTests/CommandTests.cs
index 1182fe40..c653b976 100644
--- a/Xamarin.Forms.Core.UnitTests/CommandTests.cs
+++ b/Xamarin.Forms.Core.UnitTests/CommandTests.cs
@@ -1,7 +1,6 @@
using System;
using NUnit.Framework;
-
namespace Xamarin.Forms.Core.UnitTests
{
[TestFixture]
@@ -151,5 +150,104 @@ namespace Xamarin.Forms.Core.UnitTests
Assert.AreEqual (expected, cmd.CanExecute ("Foo"));
Assert.AreEqual ("Foo", result);
}
+
+ class FakeParentContext
+ {
+ }
+
+ // ReSharper disable once ClassNeverInstantiated.Local
+ class FakeChildContext
+ {
+ }
+
+ [Test]
+ public void CanExecuteReturnsFalseIfParameterIsWrongReferenceType()
+ {
+ var command = new Command<FakeChildContext>(context => { }, context => true);
+
+ Assert.IsFalse(command.CanExecute(new FakeParentContext()), "the parameter is of the wrong type");
+ }
+
+ [Test]
+ public void CanExecuteReturnsFalseIfParameterIsWrongValueType()
+ {
+ var command = new Command<int>(context => { }, context => true);
+
+ Assert.IsFalse(command.CanExecute(10.5), "the parameter is of the wrong type");
+ }
+
+ [Test]
+ public void CanExecuteUsesParameterIfReferenceTypeAndSetToNull()
+ {
+ var command = new Command<FakeChildContext>(context => { }, context => true);
+
+ Assert.IsTrue(command.CanExecute(null), "null is a valid value for a reference type");
+ }
+
+ [Test]
+ public void CanExecuteUsesParameterIfNullableAndSetToNull()
+ {
+ var command = new Command<int?>(context => { }, context => true);
+
+ Assert.IsTrue(command.CanExecute(null), "null is a valid value for a Nullable<int> type");
+ }
+
+ [Test]
+ public void CanExecuteIgnoresParameterIfValueTypeAndSetToNull()
+ {
+ var command = new Command<int>(context => { }, context => true);
+
+ Assert.IsFalse(command.CanExecute(null), "null is not a valid valid for int");
+ }
+
+ [Test]
+ public void ExecuteDoesNotRunIfParameterIsWrongReferenceType()
+ {
+ int executions = 0;
+ var command = new Command<FakeChildContext>(context => executions += 1);
+
+ Assert.DoesNotThrow(() => command.Execute(new FakeParentContext()), "the command should not execute, so no exception should be thrown");
+ Assert.IsTrue(executions == 0, "the command should not have executed");
+ }
+
+ [Test]
+ public void ExecuteDoesNotRunIfParameterIsWrongValueType()
+ {
+ int executions = 0;
+ var command = new Command<int>(context => executions += 1);
+
+ Assert.DoesNotThrow(() => command.Execute(10.5), "the command should not execute, so no exception should be thrown");
+ Assert.IsTrue(executions == 0, "the command should not have executed");
+ }
+
+ [Test]
+ public void ExecuteRunsIfReferenceTypeAndSetToNull()
+ {
+ int executions = 0;
+ var command = new Command<FakeChildContext>(context => executions += 1);
+
+ Assert.DoesNotThrow(() => command.Execute(null), "null is a valid value for a reference type");
+ Assert.IsTrue(executions == 1, "the command should have executed");
+ }
+
+ [Test]
+ public void ExecuteRunsIfNullableAndSetToNull()
+ {
+ int executions = 0;
+ var command = new Command<int?>(context => executions += 1);
+
+ Assert.DoesNotThrow(() => command.Execute(null), "null is a valid value for a Nullable<int> type");
+ Assert.IsTrue(executions == 1, "the command should have executed");
+ }
+
+ [Test]
+ public void ExecuteDoesNotRunIfValueTypeAndSetToNull()
+ {
+ int executions = 0;
+ var command = new Command<int>(context => executions += 1);
+
+ Assert.DoesNotThrow(() => command.Execute(null), "null is not a valid value for int");
+ Assert.IsTrue(executions == 0, "the command should not have executed");
+ }
}
}
diff --git a/Xamarin.Forms.Core/Command.cs b/Xamarin.Forms.Core/Command.cs
index 73ae1b08..d15574cf 100644
--- a/Xamarin.Forms.Core/Command.cs
+++ b/Xamarin.Forms.Core/Command.cs
@@ -1,22 +1,59 @@
´╗┐using System;
+using System.Reflection;
using System.Windows.Input;
namespace Xamarin.Forms
{
- public sealed class Command<T> : Command
+ public sealed class Command<T> : Command
{
- public Command(Action<T> execute) : base(o => execute((T)o))
+ public Command(Action<T> execute)
+ : base(o =>
+ {
+ if (IsValidParameter(o))
+ {
+ execute((T)o);
+ }
+ })
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ {
+ throw new ArgumentNullException(nameof(execute));
+ }
}
- public Command(Action<T> execute, Func<T, bool> canExecute) : base(o => execute((T)o), o => canExecute((T)o))
+ public Command(Action<T> execute, Func<T, bool> canExecute)
+ : base(o =>
+ {
+ if (IsValidParameter(o))
+ {
+ execute((T)o);
+ }
+ }, o => IsValidParameter(o) && canExecute((T)o))
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
if (canExecute == null)
- throw new ArgumentNullException("canExecute");
+ throw new ArgumentNullException(nameof(canExecute));
+ }
+
+ static bool IsValidParameter(object o)
+ {
+ if (o != null)
+ {
+ // The parameter isn't null, so we don't have to worry whether null is a valid option
+ return o is T;
+ }
+
+ var t = typeof(T);
+
+ // The parameter is null. Is T Nullable?
+ if (Nullable.GetUnderlyingType(t) != null)
+ {
+ return true;
+ }
+
+ // Not a Nullable, if it's a value type then null is not valid
+ return !t.GetTypeInfo().IsValueType;
}
}
@@ -28,7 +65,7 @@ namespace Xamarin.Forms
public Command(Action<object> execute)
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
_execute = execute;
}
@@ -36,13 +73,13 @@ namespace Xamarin.Forms
public Command(Action execute) : this(o => execute())
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
}
public Command(Action<object> execute, Func<object, bool> canExecute) : this(execute)
{
if (canExecute == null)
- throw new ArgumentNullException("canExecute");
+ throw new ArgumentNullException(nameof(canExecute));
_canExecute = canExecute;
}
@@ -50,9 +87,9 @@ namespace Xamarin.Forms
public Command(Action execute, Func<bool> canExecute) : this(o => execute(), o => canExecute())
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
if (canExecute == null)
- throw new ArgumentNullException("canExecute");
+ throw new ArgumentNullException(nameof(canExecute));
}
public bool CanExecute(object parameter)
@@ -73,8 +110,7 @@ namespace Xamarin.Forms
public void ChangeCanExecute()
{
EventHandler changed = CanExecuteChanged;
- if (changed != null)
- changed(this, EventArgs.Empty);
+ changed?.Invoke(this, EventArgs.Empty);
}
}
} \ No newline at end of file