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-rw-r--r--Xamarin.Forms.Core/BindingExpression.cs506
1 files changed, 506 insertions, 0 deletions
diff --git a/Xamarin.Forms.Core/BindingExpression.cs b/Xamarin.Forms.Core/BindingExpression.cs
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+++ b/Xamarin.Forms.Core/BindingExpression.cs
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+´╗┐using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Globalization;
+using System.Linq;
+using System.Reflection;
+
+namespace Xamarin.Forms
+{
+ internal class BindingExpression
+ {
+ internal const string PropertyNotFoundErrorMessage = "'{0}' property not found on '{1}', target property: '{2}.{3}'";
+
+ readonly List<BindingExpressionPart> _parts = new List<BindingExpressionPart>();
+
+ BindableProperty _targetProperty;
+ WeakReference<object> _weakSource;
+ WeakReference<BindableObject> _weakTarget;
+
+ internal BindingExpression(BindingBase binding, string path)
+ {
+ if (binding == null)
+ throw new ArgumentNullException("binding");
+ if (path == null)
+ throw new ArgumentNullException("path");
+
+ Binding = binding;
+ Path = path;
+
+ ParsePath();
+ }
+
+ internal BindingBase Binding { get; }
+
+ internal string Path { get; }
+
+ /// <summary>
+ /// Applies the binding expression to a previously set source and target.
+ /// </summary>
+ internal void Apply(bool fromTarget = false)
+ {
+ if (_weakSource == null || _weakTarget == null)
+ return;
+
+ BindableObject target;
+ if (!_weakTarget.TryGetTarget(out target))
+ {
+ Unapply();
+ return;
+ }
+
+ object source;
+ if (_weakSource.TryGetTarget(out source) && _targetProperty != null)
+ ApplyCore(source, target, _targetProperty, fromTarget);
+ }
+
+ /// <summary>
+ /// Applies the binding expression to a new source or target.
+ /// </summary>
+ internal void Apply(object sourceObject, BindableObject target, BindableProperty property)
+ {
+ _targetProperty = property;
+
+ BindableObject prevTarget;
+ if (_weakTarget != null && _weakTarget.TryGetTarget(out prevTarget) && !ReferenceEquals(prevTarget, target))
+ throw new InvalidOperationException("Binding instances can not be reused");
+
+ object previousSource;
+ if (_weakSource != null && _weakSource.TryGetTarget(out previousSource) && !ReferenceEquals(previousSource, sourceObject))
+ throw new InvalidOperationException("Binding instances can not be reused");
+
+ _weakSource = new WeakReference<object>(sourceObject);
+ _weakTarget = new WeakReference<BindableObject>(target);
+
+ ApplyCore(sourceObject, target, property);
+ }
+
+ internal void Unapply()
+ {
+ object sourceObject;
+ if (_weakSource != null && _weakSource.TryGetTarget(out sourceObject))
+ {
+ for (var i = 0; i < _parts.Count - 1; i++)
+ {
+ BindingExpressionPart part = _parts[i];
+
+ if (!part.IsSelf)
+ {
+ part.TryGetValue(sourceObject, out sourceObject);
+ }
+
+ var inpc = sourceObject as INotifyPropertyChanged;
+ if (inpc != null)
+ inpc.PropertyChanged -= part.ChangeHandler;
+ }
+ }
+
+ _weakSource = null;
+ _weakTarget = null;
+ }
+
+ /// <summary>
+ /// Applies the binding expression to a previously set source or target.
+ /// </summary>
+ void ApplyCore(object sourceObject, BindableObject target, BindableProperty property, bool fromTarget = false)
+ {
+ BindingMode mode = Binding.GetRealizedMode(_targetProperty);
+ if (mode == BindingMode.OneWay && fromTarget)
+ return;
+
+ bool needsGetter = (mode == BindingMode.TwoWay && !fromTarget) || mode == BindingMode.OneWay;
+ bool needsSetter = !needsGetter && ((mode == BindingMode.TwoWay && fromTarget) || mode == BindingMode.OneWayToSource);
+
+ object current = sourceObject;
+ object previous = null;
+ BindingExpressionPart part = null;
+
+ for (var i = 0; i < _parts.Count; i++)
+ {
+ part = _parts[i];
+ bool isLast = i + 1 == _parts.Count;
+
+ if (!part.IsSelf && current != null)
+ {
+ // Allow the object instance itself to provide its own TypeInfo
+ var reflectable = current as IReflectableType;
+ TypeInfo currentType = reflectable != null ? reflectable.GetTypeInfo() : current.GetType().GetTypeInfo();
+ if (part.LastGetter == null || !part.LastGetter.DeclaringType.GetTypeInfo().IsAssignableFrom(currentType))
+ SetupPart(currentType, part);
+
+ if (!isLast)
+ part.TryGetValue(current, out current);
+ }
+
+ if (!part.IsSelf && current != null)
+ {
+ if ((needsGetter && part.LastGetter == null) || (needsSetter && part.NextPart == null && part.LastSetter == null))
+ {
+ Log.Warning("Binding", PropertyNotFoundErrorMessage, part.Content, current, target.GetType(), property.PropertyName);
+ break;
+ }
+ }
+
+ if (mode == BindingMode.OneWay || mode == BindingMode.TwoWay)
+ {
+ var inpc = current as INotifyPropertyChanged;
+ if (inpc != null && !ReferenceEquals(current, previous))
+ {
+ // If we're reapplying, we don't want to double subscribe
+ inpc.PropertyChanged -= part.ChangeHandler;
+ inpc.PropertyChanged += part.ChangeHandler;
+ }
+ }
+
+ previous = current;
+ }
+
+ Debug.Assert(part != null, "There should always be at least the self part in the expression.");
+
+ if (needsGetter)
+ {
+ object value = property.DefaultValue;
+ if (part.TryGetValue(current, out value) || part.IsSelf)
+ {
+ value = Binding.GetSourceValue(value, property.ReturnType);
+ }
+ else
+ value = property.DefaultValue;
+
+ if (!TryConvert(part, ref value, property.ReturnType, true))
+ {
+ Log.Warning("Binding", "{0} can not be converted to type '{1}'", value, property.ReturnType);
+ return;
+ }
+
+ target.SetValueCore(property, value, BindableObject.SetValueFlags.ClearDynamicResource, BindableObject.SetValuePrivateFlags.Default | BindableObject.SetValuePrivateFlags.Converted);
+ }
+ else if (needsSetter && part.LastSetter != null && current != null)
+ {
+ object value = Binding.GetTargetValue(target.GetValue(property), part.SetterType);
+
+ if (!TryConvert(part, ref value, part.SetterType, false))
+ {
+ Log.Warning("Binding", "{0} can not be converted to type '{1}'", value, part.SetterType);
+ return;
+ }
+
+ object[] args;
+ if (part.IsIndexer)
+ {
+ args = new object[part.Arguments.Length + 1];
+ part.Arguments.CopyTo(args, 0);
+ args[args.Length - 1] = value;
+ }
+ else if (part.IsBindablePropertySetter)
+ {
+ args = new[] { part.BindablePropertyField, value };
+ }
+ else
+ {
+ args = new[] { value };
+ }
+
+ part.LastSetter.Invoke(current, args);
+ }
+ }
+
+ IEnumerable<BindingExpressionPart> GetPart(string part)
+ {
+ part = part.Trim();
+ if (part == string.Empty)
+ throw new FormatException("Path contains an empty part");
+
+ BindingExpressionPart indexer = null;
+
+ int lbIndex = part.IndexOf('[');
+ if (lbIndex != -1)
+ {
+ int rbIndex = part.LastIndexOf(']');
+ if (rbIndex == -1)
+ throw new FormatException("Indexer did not contain closing bracket");
+
+ int argLength = rbIndex - lbIndex - 1;
+ if (argLength == 0)
+ throw new FormatException("Indexer did not contain arguments");
+
+ string argString = part.Substring(lbIndex + 1, argLength);
+ indexer = new BindingExpressionPart(this, argString, true);
+
+ part = part.Substring(0, lbIndex);
+ part = part.Trim();
+ }
+
+ if (part.Length > 0)
+ yield return new BindingExpressionPart(this, part);
+ if (indexer != null)
+ yield return indexer;
+ }
+
+ void ParsePath()
+ {
+ string p = Path.Trim();
+
+ var last = new BindingExpressionPart(this, ".");
+ _parts.Add(last);
+
+ if (p[0] == '.')
+ {
+ if (p.Length == 1)
+ return;
+
+ p = p.Substring(1);
+ }
+
+ string[] pathParts = p.Split('.');
+ for (var i = 0; i < pathParts.Length; i++)
+ {
+ foreach (BindingExpressionPart part in GetPart(pathParts[i]))
+ {
+ last.NextPart = part;
+ _parts.Add(part);
+ last = part;
+ }
+ }
+ }
+
+ void SetupPart(TypeInfo sourceType, BindingExpressionPart part)
+ {
+ part.Arguments = null;
+ part.LastGetter = null;
+ part.LastSetter = null;
+
+ PropertyInfo property = null;
+ if (part.IsIndexer)
+ {
+ if (sourceType.IsArray)
+ {
+ int index;
+ if (!int.TryParse(part.Content, out index))
+ Log.Warning("Binding", "{0} could not be parsed as an index for a {1}", part.Content, sourceType);
+ else
+ part.Arguments = new object[] { index };
+
+ part.LastGetter = sourceType.GetDeclaredMethod("Get");
+ part.LastSetter = sourceType.GetDeclaredMethod("Set");
+ part.SetterType = sourceType.GetElementType();
+ }
+
+ DefaultMemberAttribute defaultMember = sourceType.GetCustomAttributes(typeof(DefaultMemberAttribute), true).OfType<DefaultMemberAttribute>().FirstOrDefault();
+ string indexerName = defaultMember != null ? defaultMember.MemberName : "Item";
+
+ part.IndexerName = indexerName;
+
+ property = sourceType.GetDeclaredProperty(indexerName);
+ if (property == null)
+ property = sourceType.BaseType.GetProperty(indexerName);
+
+ if (property != null)
+ {
+ ParameterInfo parameter = property.GetIndexParameters().FirstOrDefault();
+ if (parameter != null)
+ {
+ try
+ {
+ object arg = Convert.ChangeType(part.Content, parameter.ParameterType, CultureInfo.InvariantCulture);
+ part.Arguments = new[] { arg };
+ }
+ catch (FormatException)
+ {
+ }
+ catch (InvalidCastException)
+ {
+ }
+ catch (OverflowException)
+ {
+ }
+ }
+ }
+ }
+ else
+ {
+ property = sourceType.GetDeclaredProperty(part.Content);
+ if (property == null)
+ property = sourceType.BaseType.GetProperty(part.Content);
+ }
+
+ if (property != null)
+ {
+ if (property.CanRead && property.GetMethod.IsPublic && !property.GetMethod.IsStatic)
+ part.LastGetter = property.GetMethod;
+ if (property.CanWrite && property.SetMethod.IsPublic && !property.SetMethod.IsStatic)
+ {
+ part.LastSetter = property.SetMethod;
+ part.SetterType = part.LastSetter.GetParameters().Last().ParameterType;
+
+ if (Binding.AllowChaining)
+ {
+ FieldInfo bindablePropertyField = sourceType.GetDeclaredField(part.Content + "Property");
+ if (bindablePropertyField != null && bindablePropertyField.FieldType == typeof(BindableProperty) && sourceType.ImplementedInterfaces.Contains(typeof(IElementController)))
+ {
+ MethodInfo setValueMethod = null;
+ foreach (MethodInfo m in sourceType.AsType().GetRuntimeMethods())
+ {
+ if (m.Name.EndsWith("IElementController.SetValueFromRenderer"))
+ {
+ ParameterInfo[] parameters = m.GetParameters();
+ if (parameters.Length == 2 && parameters[0].ParameterType == typeof(BindableProperty))
+ {
+ setValueMethod = m;
+ break;
+ }
+ }
+ }
+ if (setValueMethod != null)
+ {
+ part.LastSetter = setValueMethod;
+ part.IsBindablePropertySetter = true;
+ part.BindablePropertyField = bindablePropertyField.GetValue(null);
+ }
+ }
+ }
+ }
+ }
+ }
+
+ bool TryConvert(BindingExpressionPart part, ref object value, Type convertTo, bool toTarget)
+ {
+ if (value == null)
+ return true;
+ if ((toTarget && _targetProperty.TryConvert(ref value)) || (!toTarget && convertTo.IsInstanceOfType(value)))
+ return true;
+
+ object original = value;
+ try
+ {
+ value = Convert.ChangeType(value, convertTo, CultureInfo.InvariantCulture);
+ return true;
+ }
+ catch (InvalidCastException)
+ {
+ value = original;
+ return false;
+ }
+ catch (FormatException)
+ {
+ value = original;
+ return false;
+ }
+ catch (OverflowException)
+ {
+ value = original;
+ return false;
+ }
+ }
+
+ class BindingPair
+ {
+ public BindingPair(BindingExpressionPart part, object source, bool isLast)
+ {
+ Part = part;
+ Source = source;
+ IsLast = isLast;
+ }
+
+ public bool IsLast { get; set; }
+
+ public BindingExpressionPart Part { get; private set; }
+
+ public object Source { get; private set; }
+ }
+
+ class BindingExpressionPart
+ {
+ readonly BindingExpression _expression;
+
+ public readonly PropertyChangedEventHandler ChangeHandler;
+
+ public BindingExpressionPart(BindingExpression expression, string content, bool isIndexer = false)
+ {
+ _expression = expression;
+ IsSelf = content == Forms.Binding.SelfPath;
+ Content = content;
+ IsIndexer = isIndexer;
+
+ ChangeHandler = PropertyChanged;
+ }
+
+ public object[] Arguments { get; set; }
+
+ public object BindablePropertyField { get; set; }
+
+ public string Content { get; }
+
+ public string IndexerName { get; set; }
+
+ public bool IsBindablePropertySetter { get; set; }
+
+ public bool IsIndexer { get; }
+
+ public bool IsSelf { get; }
+
+ public MethodInfo LastGetter { get; set; }
+
+ public MethodInfo LastSetter { get; set; }
+
+ public BindingExpressionPart NextPart { get; set; }
+
+ public Type SetterType { get; set; }
+
+ public void PropertyChanged(object sender, PropertyChangedEventArgs args)
+ {
+ BindingExpressionPart part = NextPart ?? this;
+
+ string name = args.PropertyName;
+
+ if (!string.IsNullOrEmpty(name))
+ {
+ if (part.IsIndexer)
+ {
+ if (name.Contains("["))
+ {
+ if (name != string.Format("{0}[{1}]", part.IndexerName, part.Content))
+ return;
+ }
+ else if (name != part.IndexerName)
+ return;
+ }
+ else if (name != part.Content)
+ {
+ return;
+ }
+ }
+
+ Device.BeginInvokeOnMainThread(() => _expression.Apply());
+ }
+
+ public bool TryGetValue(object source, out object value)
+ {
+ value = source;
+
+ if (LastGetter != null && value != null)
+ {
+ if (IsIndexer)
+ {
+ try
+ {
+ value = LastGetter.Invoke(value, Arguments);
+ }
+ catch (TargetInvocationException ex)
+ {
+ if (!(ex.InnerException is KeyNotFoundException))
+ throw;
+ value = null;
+ }
+ return true;
+ }
+ value = LastGetter.Invoke(value, Arguments);
+ return true;
+ }
+
+ return false;
+ }
+ }
+ }
+} \ No newline at end of file