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  • Are super methods in JavaScript limited to functional inheritance, as per Crockford's book?

    - by kindohm
    In Douglas Crockford's "JavaScript: The Good Parts", he walks through three types of inheritance: classical, prototypal, and functional. In the part on functional inheritance he writes: "The functional pattern also gives us a way to deal with super methods." He then goes on to implement a method named "superior" on all Objects. However, in the way he uses the superior method, it just looks like he is copying the method on the super object for later use: // crockford's code: var coolcat = function(spec) { var that = cat(spec), super_get_name = that.superior('get_name'); that.get_name = function (n) { return 'like ' + super_get_name() + ' baby'; }; return that; }; The original get_name method is copied to super_get_name. I don't get what's so special about functional inheritance that makes this possible. Can't you do this with classical or prototypal inheritance? What's the difference between the code above and the code below: var CoolCat = function(name) { this.name = name; } CoolCat.prototype = new Cat(); CoolCat.prototype.super_get_name = CoolCat.prototype.get_name; CoolCat.prototype.get_name = function (n) { return 'like ' + this.super_get_name() + ' baby'; }; Doesn't this second example provide access to "super methods" too?

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  • NullReferenceException when changing skin/theme via Application.Current.Resources

    - by CoolCat
    I am writing an wpf application with multiple skins. The code to switch theme is as below: try { Application.Current.Resources.MergedDictionaries.Add( resource ); } catch( Exception ex ) { } The first time the code is called (to switch to a new theme), it is executed successfully; however, any subsequent calls to the same code would throw System.NullReferenceException. The way I set up my themes are similar to what described here: http://www.codewrecks.com/blog/index.php/2008/05/22/simple-skinnable-and-theme-management-in-wpf-user-interface/. Has anyone seen this error before? How do I go about debugging this since the exception is thrown else where? Any help is greatly appreciated. StackTrace: at System.Windows.EffectiveValueEntry.GetFlattenedEntry(RequestFlags requests) at System.Windows.DependencyObject.EvaluateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry newEntry, OperationType operationType) at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType) at System.Windows.StyleHelper.ApplyStyleOrTemplateValue(FrameworkObject fo, DependencyProperty dp) at System.Windows.StyleHelper.InvalidateContainerDependents(DependencyObject container, FrugalStructList`1& exclusionContainerDependents, FrugalStructList`1& oldContainerDependents, FrugalStructList`1& newContainerDependents) at System.Windows.StyleHelper.DoStyleInvalidations(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle) at System.Windows.StyleHelper.UpdateStyleCache(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle, Style& styleCache) at System.Windows.FrameworkElement.OnStyleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e) at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e) at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args) at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType) at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp) at System.Windows.FrameworkElement.UpdateStyleProperty() at System.Windows.TreeWalkHelper.InvalidateStyleAndReferences(DependencyObject d, ResourcesChangeInfo info, Boolean containsTypeOfKey) at System.Windows.TreeWalkHelper.OnResourcesChanged(DependencyObject d, ResourcesChangeInfo info, Boolean raiseResourceChangedEvent) at System.Windows.TreeWalkHelper.OnResourcesChangedCallback(DependencyObject d, ResourcesChangeInfo info) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1.StartWalk(DependencyObject startNode, Boolean skipStartNode) at System.Windows.TreeWalkHelper.InvalidateOnResourcesChange(FrameworkElement fe, FrameworkContentElement fce, ResourcesChangeInfo info) at System.Windows.Application.InvalidateResourceReferenceOnWindowCollection(WindowCollection wc, ResourcesChangeInfo info) at System.Windows.ResourceDictionary.NotifyOwners(ResourcesChangeInfo info) at System.Windows.ResourceDictionary.OnMergedDictionariesChanged(Object sender, NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item) at System.Windows.ResourceDictionaryCollection.InsertItem(Int32 index, ResourceDictionary item) at System.Collections.ObjectModel.Collection`1.Add(T item)

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