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• What if globals make sense?

  - by Greg

  I've got a value that many objects need. For example, a financial application with different investments as objects, and most of them need the current interest rate. I was hoping to encapsulate my "financial environment" as an object, with the interest rate as a property. But, sibling objects that need that value can't get to it. So how do I share values among many objects without over-coupling my design? Obviously I'm thinking about this wrong.

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• What is the difference between "data hiding" and "encapsulation"?

  - by Software Engeneering Learner

  I'm reading "Java concurrency in practice" and there is said: "Fortunately, the same object-oriented techniques that help you write well-organized, maintainable classes - such as encapsulation and data hiding -can also help you create thread-safe classes." The problem #1 - I never heard about data hiding and don't know what it is. The problem #2 - I always thought that encapsulation is using private vs public, and is actually the data hiding. Can you please explain what data hiding is and how it differs from encapsulation?

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• Are UML class diagrams adequate to design javascript systems?

  - by Vandell

  Given that UML is oriented towards a more classic approach to object orientation, is it still usable in a reliable way to design javascript systems? One specific problem that I can see is that class diagrams are, in fact, a structural view of the system, and javascript is more behaviour driven, how can you deal with it? Please, keep in mind that I'm not talking abot the real world domain here, It's a model for the solution that I'm trying to achieve.

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• Computer Engineer in CS Interview

  - by blasteye

  As a Computer Engineering student, while in school I've primarily dealt with C, Matlab, and VHDL. On my own though, i learned a bit about OOP (Polymorphism, inheritance, encapsulation), and have done quite a bit of web development using JavaScript/PHP/Node.js While at coding interviews I've be asked academia CS questions such as "abstract vs interface". The problem is that I didn't know the official terminology, but I have dealt with this type of programming decisions/concepts. Could anyone recommend a good resource for me to learn these academia CS terms?

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• How to store multiple requirements with OR and AND?

  - by Cano

  Well I'm working on a personal project that needs to check if a user has met certain requirements, and they come in a form of Requirement: [c1 OR c2] AND [d1 OR d2] Requirement: [c1 AND c2] OR [d1 AND d2] Requirement: c1 AND any dn(n can be any integer) I'm just not sure how to store these sorts of requirements, I'm thinking of using another object to hold c1,c2,d1,d2....dn and OR, but that seems like a roundabout way of doing things. Is there a better method?

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• Can't Drag & Drop text to unity launcher (e.g. url's, highlighted text)

  - by patsee

  I'm trying to create a unity launcher icon (.dekstop file) on which you can drop any (selected/highlighted) text from a web browser, google chrome in my case. I know you can use the "MimeType=" key in a .desktop file, but I can't find the right mime type for my scenario. I've tried several text MimeTypes and "text/*", but none of them would work. Does anyone know which MimeType I have to use in order for my launcher icon to accept text when hovering over it?

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• How to handle status columns in designing tables

  - by altsyset

  How to handle multiple statuses for a table entry, for example an item table may have an active, inactive, fast moving, and/or batch statuses. And I wanted to handle them in single column with VARCHAR type. Also I might set each of those attributes as a boolean with different columns. But I am not sure what consequences this might lead to. So if you have experienced such situations which one would be the best way to handle it?

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• An Xml Serializable PropertyBag Dictionary Class for .NET

  - by Rick Strahl

  I don't know about you but I frequently need property bags in my applications to store and possibly cache arbitrary data. Dictionary<T,V> works well for this although I always seem to be hunting for a more specific generic type that provides a string key based dictionary. There's string dictionary, but it only works with strings. There's Hashset<T> but it uses the actual values as keys. In most key value pair situations for me string is key value to work off. Dictionary<T,V> works well enough, but there are some issues with serialization of dictionaries in .NET. The .NET framework doesn't do well serializing IDictionary objects out of the box. The XmlSerializer doesn't support serialization of IDictionary via it's default serialization, and while the DataContractSerializer does support IDictionary serialization it produces some pretty atrocious XML. What doesn't work? First off Dictionary serialization with the Xml Serializer doesn't work so the following fails: [TestMethod] public void DictionaryXmlSerializerTest() { var bag = new Dictionary<string, object>(); bag.Add("key", "Value"); bag.Add("Key2", 100.10M); bag.Add("Key3", Guid.NewGuid()); bag.Add("Key4", DateTime.Now); bag.Add("Key5", true); bag.Add("Key7", new byte[3] { 42, 45, 66 }); TestContext.WriteLine(this.ToXml(bag)); } public string ToXml(object obj) { if (obj == null) return null; StringWriter sw = new StringWriter(); XmlSerializer ser = new XmlSerializer(obj.GetType()); ser.Serialize(sw, obj); return sw.ToString(); } The error you get with this is: System.NotSupportedException: The type System.Collections.Generic.Dictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] is not supported because it implements IDictionary. Got it! BTW, the same is true with binary serialization. Running the same code above against the DataContractSerializer does work: [TestMethod] public void DictionaryDataContextSerializerTest() { var bag = new Dictionary<string, object>(); bag.Add("key", "Value"); bag.Add("Key2", 100.10M); bag.Add("Key3", Guid.NewGuid()); bag.Add("Key4", DateTime.Now); bag.Add("Key5", true); bag.Add("Key7", new byte[3] { 42, 45, 66 }); TestContext.WriteLine(this.ToXmlDcs(bag)); } public string ToXmlDcs(object value, bool throwExceptions = false) { var ser = new DataContractSerializer(value.GetType(), null, int.MaxValue, true, false, null); MemoryStream ms = new MemoryStream(); ser.WriteObject(ms, value); return Encoding.UTF8.GetString(ms.ToArray(), 0, (int)ms.Length); } This DOES work but produces some pretty heinous XML (formatted with line breaks and indentation here): <ArrayOfKeyValueOfstringanyType xmlns="http://schemas.microsoft.com/2003/10/Serialization/Arrays" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <KeyValueOfstringanyType> <Key>key</Key> <Value i:type="a:string" xmlns:a="http://www.w3.org/2001/XMLSchema">Value</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key2</Key> <Value i:type="a:decimal" xmlns:a="http://www.w3.org/2001/XMLSchema">100.10</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key3</Key> <Value i:type="a:guid" xmlns:a="http://schemas.microsoft.com/2003/10/Serialization/">2cd46d2a-a636-4af4-979b-e834d39b6d37</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key4</Key> <Value i:type="a:dateTime" xmlns:a="http://www.w3.org/2001/XMLSchema">2011-09-19T17:17:05.4406999-07:00</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key5</Key> <Value i:type="a:boolean" xmlns:a="http://www.w3.org/2001/XMLSchema">true</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key7</Key> <Value i:type="a:base64Binary" xmlns:a="http://www.w3.org/2001/XMLSchema">Ki1C</Value> </KeyValueOfstringanyType> </ArrayOfKeyValueOfstringanyType> Ouch! That seriously hurts the eye! :-) Worse though it's extremely verbose with all those repetitive namespace declarations. It's good to know that it works in a pinch, but for a human readable/editable solution or something lightweight to store in a database it's not quite ideal. Why should I care? As a little background, in one of my applications I have a need for a flexible property bag that is used on a free form database field on an otherwise static entity. Basically what I have is a standard database record to which arbitrary properties can be added in an XML based string field. I intend to expose those arbitrary properties as a collection from field data stored in XML. The concept is pretty simple: When loading write the data to the collection, when the data is saved serialize the data into an XML string and store it into the database. When reading the data pick up the XML and if the collection on the entity is accessed automatically deserialize the XML into the Dictionary. (I'll talk more about this in another post). While the DataContext Serializer would work, it's verbosity is problematic both for size of the generated XML strings and the fact that users can manually edit this XML based property data in an advanced mode. A clean(er) layout certainly would be preferable and more user friendly. Custom XMLSerialization with a PropertyBag Class So… after a bunch of experimentation with different serialization formats I decided to create a custom PropertyBag class that provides for a serializable Dictionary. It's basically a custom Dictionary<TType,TValue> implementation with the keys always set as string keys. The result are PropertyBag<TValue> and PropertyBag (which defaults to the object type for values). The PropertyBag<TType> and PropertyBag classes provide these features: Subclassed from Dictionary<T,V> Implements IXmlSerializable with a cleanish XML format ToXml() and FromXml() methods to export and import to and from XML strings Static CreateFromXml() method to create an instance It's simple enough as it's merely a Dictionary<string,object> subclass but that supports serialization to a - what I think at least - cleaner XML format. The class is super simple to use: [TestMethod] public void PropertyBagTwoWayObjectSerializationTest() { var bag = new PropertyBag(); bag.Add("key", "Value"); bag.Add("Key2", 100.10M); bag.Add("Key3", Guid.NewGuid()); bag.Add("Key4", DateTime.Now); bag.Add("Key5", true); bag.Add("Key7", new byte[3] { 42,45,66 } ); bag.Add("Key8", null); bag.Add("Key9", new ComplexObject() { Name = "Rick", Entered = DateTime.Now, Count = 10 }); string xml = bag.ToXml(); TestContext.WriteLine(bag.ToXml()); bag.Clear(); bag.FromXml(xml); Assert.IsTrue(bag["key"] as string == "Value"); Assert.IsInstanceOfType( bag["Key3"], typeof(Guid)); Assert.IsNull(bag["Key8"]); //Assert.IsNull(bag["Key10"]); Assert.IsInstanceOfType(bag["Key9"], typeof(ComplexObject)); } This uses the PropertyBag class which uses a PropertyBag<string,object> - which means it returns untyped values of type object. I suspect for me this will be the most common scenario as I'd want to store arbitrary values in the PropertyBag rather than one specific type. The same code with a strongly typed PropertyBag<decimal> looks like this: [TestMethod] public void PropertyBagTwoWayValueTypeSerializationTest() { var bag = new PropertyBag<decimal>(); bag.Add("key", 10M); bag.Add("Key1", 100.10M); bag.Add("Key2", 200.10M); bag.Add("Key3", 300.10M); string xml = bag.ToXml(); TestContext.WriteLine(bag.ToXml()); bag.Clear(); bag.FromXml(xml); Assert.IsTrue(bag.Get("Key1") == 100.10M); Assert.IsTrue(bag.Get("Key3") == 300.10M); } and produces typed results of type decimal. The types can be either value or reference types the combination of which actually proved to be a little more tricky than anticipated due to null and specific string value checks required - getting the generic typing right required use of default(T) and Convert.ChangeType() to trick the compiler into playing nice. Of course the whole raison d'etre for this class is the XML serialization. You can see in the code above that we're doing a .ToXml() and .FromXml() to serialize to and from string. The XML produced for the first example looks like this: <?xml version="1.0" encoding="utf-8"?> <properties> <item> <key>key</key> <value>Value</value> </item> <item> <key>Key2</key> <value type="decimal">100.10</value> </item> <item> <key>Key3</key> <value type="___System.Guid"> <guid>f7a92032-0c6d-4e9d-9950-b15ff7cd207d</guid> </value> </item> <item> <key>Key4</key> <value type="datetime">2011-09-26T17:45:58.5789578-10:00</value> </item> <item> <key>Key5</key> <value type="boolean">true</value> </item> <item> <key>Key7</key> <value type="base64Binary">Ki1C</value> </item> <item> <key>Key8</key> <value type="nil" /> </item> <item> <key>Key9</key> <value type="___Westwind.Tools.Tests.PropertyBagTest+ComplexObject"> <ComplexObject> <Name>Rick</Name> <Entered>2011-09-26T17:45:58.5789578-10:00</Entered> <Count>10</Count> </ComplexObject> </value> </item> </properties>   The format is a bit cleaner than the DataContractSerializer. Each item is serialized into <key> <value> pairs. If the value is a string no type information is written. Since string tends to be the most common type this saves space and serialization processing. All other types are attributed. Simple types are mapped to XML types so things like decimal, datetime, boolean and base64Binary are encoded using their Xml type values. All other types are embedded with a hokey format that describes the .NET type preceded by a three underscores and then are encoded using the XmlSerializer. You can see this best above in the ComplexObject encoding. For custom types this isn't pretty either, but it's more concise than the DCS and it works as long as you're serializing back and forth between .NET clients at least. The XML generated from the second example that uses PropertyBag<decimal> looks like this: <?xml version="1.0" encoding="utf-8"?> <properties> <item> <key>key</key> <value type="decimal">10</value> </item> <item> <key>Key1</key> <value type="decimal">100.10</value> </item> <item> <key>Key2</key> <value type="decimal">200.10</value> </item> <item> <key>Key3</key> <value type="decimal">300.10</value> </item> </properties>   How does it work As I mentioned there's nothing fancy about this solution - it's little more than a subclass of Dictionary<T,V> that implements custom Xml Serialization and a couple of helper methods that facilitate getting the XML in and out of the class more easily. But it's proven very handy for a number of projects for me where dynamic data storage is required. Here's the code: /// <summary> /// Creates a serializable string/object dictionary that is XML serializable /// Encodes keys as element names and values as simple values with a type /// attribute that contains an XML type name. Complex names encode the type /// name with type='___namespace.classname' format followed by a standard xml /// serialized format. The latter serialization can be slow so it's not recommended /// to pass complex types if performance is critical. /// </summary> [XmlRoot("properties")] public class PropertyBag : PropertyBag<object> { /// <summary> /// Creates an instance of a propertybag from an Xml string /// </summary> /// <param name="xml">Serialize</param> /// <returns></returns> public static PropertyBag CreateFromXml(string xml) { var bag = new PropertyBag(); bag.FromXml(xml); return bag; } } /// <summary> /// Creates a serializable string for generic types that is XML serializable. /// /// Encodes keys as element names and values as simple values with a type /// attribute that contains an XML type name. Complex names encode the type /// name with type='___namespace.classname' format followed by a standard xml /// serialized format. The latter serialization can be slow so it's not recommended /// to pass complex types if performance is critical. /// </summary> /// <typeparam name="TValue">Must be a reference type. For value types use type object</typeparam> [XmlRoot("properties")] public class PropertyBag<TValue> : Dictionary<string, TValue>, IXmlSerializable { /// <summary> /// Not implemented - this means no schema information is passed /// so this won't work with ASMX/WCF services. /// </summary> /// <returns></returns> public System.Xml.Schema.XmlSchema GetSchema() { return null; } /// <summary> /// Serializes the dictionary to XML. Keys are /// serialized to element names and values as /// element values. An xml type attribute is embedded /// for each serialized element - a .NET type /// element is embedded for each complex type and /// prefixed with three underscores. /// </summary> /// <param name="writer"></param> public void WriteXml(System.Xml.XmlWriter writer) { foreach (string key in this.Keys) { TValue value = this[key]; Type type = null; if (value != null) type = value.GetType(); writer.WriteStartElement("item"); writer.WriteStartElement("key"); writer.WriteString(key as string); writer.WriteEndElement(); writer.WriteStartElement("value"); string xmlType = XmlUtils.MapTypeToXmlType(type); bool isCustom = false; // Type information attribute if not string if (value == null) { writer.WriteAttributeString("type", "nil"); } else if (!string.IsNullOrEmpty(xmlType)) { if (xmlType != "string") { writer.WriteStartAttribute("type"); writer.WriteString(xmlType); writer.WriteEndAttribute(); } } else { isCustom = true; xmlType = "___" + value.GetType().FullName; writer.WriteStartAttribute("type"); writer.WriteString(xmlType); writer.WriteEndAttribute(); } // Actual deserialization if (!isCustom) { if (value != null) writer.WriteValue(value); } else { XmlSerializer ser = new XmlSerializer(value.GetType()); ser.Serialize(writer, value); } writer.WriteEndElement(); // value writer.WriteEndElement(); // item } } /// <summary> /// Reads the custom serialized format /// </summary> /// <param name="reader"></param> public void ReadXml(System.Xml.XmlReader reader) { this.Clear(); while (reader.Read()) { if (reader.NodeType == XmlNodeType.Element && reader.Name == "key") { string xmlType = null; string name = reader.ReadElementContentAsString(); // item element reader.ReadToNextSibling("value"); if (reader.MoveToNextAttribute()) xmlType = reader.Value; reader.MoveToContent(); TValue value; if (xmlType == "nil") value = default(TValue); // null else if (string.IsNullOrEmpty(xmlType)) { // value is a string or object and we can assign TValue to value string strval = reader.ReadElementContentAsString(); value = (TValue) Convert.ChangeType(strval, typeof(TValue)); } else if (xmlType.StartsWith("___")) { while (reader.Read() && reader.NodeType != XmlNodeType.Element) { } Type type = ReflectionUtils.GetTypeFromName(xmlType.Substring(3)); //value = reader.ReadElementContentAs(type,null); XmlSerializer ser = new XmlSerializer(type); value = (TValue)ser.Deserialize(reader); } else value = (TValue)reader.ReadElementContentAs(XmlUtils.MapXmlTypeToType(xmlType), null); this.Add(name, value); } } } /// <summary> /// Serializes this dictionary to an XML string /// </summary> /// <returns>XML String or Null if it fails</returns> public string ToXml() { string xml = null; SerializationUtils.SerializeObject(this, out xml); return xml; } /// <summary> /// Deserializes from an XML string /// </summary> /// <param name="xml"></param> /// <returns>true or false</returns> public bool FromXml(string xml) { this.Clear(); // if xml string is empty we return an empty dictionary if (string.IsNullOrEmpty(xml)) return true; var result = SerializationUtils.DeSerializeObject(xml, this.GetType()) as PropertyBag<TValue>; if (result != null) { foreach (var item in result) { this.Add(item.Key, item.Value); } } else // null is a failure return false; return true; } /// <summary> /// Creates an instance of a propertybag from an Xml string /// </summary> /// <param name="xml"></param> /// <returns></returns> public static PropertyBag<TValue> CreateFromXml(string xml) { var bag = new PropertyBag<TValue>(); bag.FromXml(xml); return bag; } } } The code uses a couple of small helper classes SerializationUtils and XmlUtils for mapping Xml types to and from .NET, both of which are from the WestWind,Utilities project (which is the same project where PropertyBag lives) from the West Wind Web Toolkit. The code implements ReadXml and WriteXml for the IXmlSerializable implementation using old school XmlReaders and XmlWriters (because it's pretty simple stuff - no need for XLinq here). Then there are two helper methods .ToXml() and .FromXml() that basically allow your code to easily convert between XML and a PropertyBag object. In my code that's what I use to actually to persist to and from the entity XML property during .Load() and .Save() operations. It's sweet to be able to have a string key dictionary and then be able to turn around with 1 line of code to persist the whole thing to XML and back. Hopefully some of you will find this class as useful as I've found it. It's a simple solution to a common requirement in my applications and I've used the hell out of it in the  short time since I created it. Resources You can find the complete code for the two classes plus the helpers in the Subversion repository for Westwind.Utilities. You can grab the source files from there or download the whole project. You can also grab the full Westwind.Utilities assembly from NuGet and add it to your project if that's easier for you. PropertyBag Source Code SerializationUtils and XmlUtils Westwind.Utilities Assembly on NuGet (add from Visual Studio) © Rick Strahl, West Wind Technologies, 2005-2011Posted in .NET  CSharp   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Handling null values and missing object properties in Silverlight 4

  - by PeterTweed

  Before Silverlight 4 to bind a data object to the UI and display a message associated with either a null value or if the binding path was wrong, you would need to write a Converter.  In Silverlight 4 we find the addition of the markup extensions TargetNullValue and FallbackValue that allows us to display a value when a null value is found in the bound to property and display a value when the property being bound to is not found. This post will show you how to use both markup extensions. Steps: 1. Create a new Silverlight 4 application 2. In the body of the MainPage.xaml.cs file replace the MainPage class with the following code:     public partial class MainPage : UserControl     {         public MainPage()         {             InitializeComponent();             this.Loaded += new RoutedEventHandler(MainPage_Loaded);         }           void MainPage_Loaded(object sender, RoutedEventArgs e)         {             person p = new person() { NameValue = "Peter Tweed" };             this.DataContext = p;         }     }       public class person     {         public string NameValue { get; set; }         public string TitleValue { get; set; }     } This code defines a class called person with two properties.  A new instance of the class is created, only defining the value for one of the properties and bound to the DataContext of the page. 3.  In the MainPage.xaml file copy the following XAML into the LayoutRoot grid:         <Grid.RowDefinitions>             <RowDefinition Height="60*" />             <RowDefinition Height="28*" />             <RowDefinition Height="28*" />             <RowDefinition Height="30*" />             <RowDefinition Height="154*" />         </Grid.RowDefinitions>         <Grid.ColumnDefinitions>             <ColumnDefinition Width="86*" />             <ColumnDefinition Width="314*" />         </Grid.ColumnDefinitions>         <TextBlock Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock1" Text="Name Value:" VerticalAlignment="Top" />         <TextBlock Grid.Row="2" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock2" Text="Title Value:" VerticalAlignment="Top" />         <TextBlock Grid.Row="3" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock3" Text="Non Existant Value:" VerticalAlignment="Top" />         <TextBlock Grid.Column="1" Grid.Row="1" Height="23" HorizontalAlignment="Left" Name="textBlock4" Text="{Binding NameValue, TargetNullValue='No Name!!!!!!!'}" VerticalAlignment="Top" Margin="6,0,0,0" />         <TextBlock Grid.Column="1" Grid.Row="2" Height="23" HorizontalAlignment="Left" Name="textBlock5" Text="{Binding TitleValue, TargetNullValue='No Title!!!!!!!'}" VerticalAlignment="Top" Margin="6,0,0,0" />         <TextBlock Grid.Column="1" Grid.Row="3" Height="23" HorizontalAlignment="Left" Margin="6,0,0,0" Name="textBlock6" Text="{Binding AgeValue, FallbackValue='No such property!'}" VerticalAlignment="Top" />    This XAML defines three textblocks – two of which use the TargetNull and one that uses the FallbackValue markup extensions.  4. Run the application and see the person name displayed as defined for the person object, the expected string displayed for the TargetNullValue when no value exists for the boudn property and the expected string displayed for the FallbackValue when the property bound to is not found on the bound object. It's that easy!

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• OpenGL Fast-Object Instancing Error

  - by HJ Media Studios

  I have some code that loops through a set of objects and renders instances of those objects. The list of objects that needs to be rendered is stored as a std::map, where an object of class MeshResource contains the vertices and indices with the actual data, and an object of classMeshRenderer defines the point in space the mesh is to be rendered at. My rendering code is as follows: glDisable(GL_BLEND); glEnable(GL_CULL_FACE); glDepthMask(GL_TRUE); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); for (std::map<MeshResource*, std::vector<MeshRenderer*> >::iterator it = renderables.begin(); it != renderables.end(); it++) { it->first->setupBeforeRendering(); cout << "<"; for (unsigned long i =0; i < it->second.size(); i++) { //Pass in an identity matrix to the vertex shader- used here only for debugging purposes; the real code correctly inputs any matrix. uniformizeModelMatrix(Matrix4::IDENTITY); /** * StartHere fix rendering problem. * Ruled out: * Vertex buffers correctly. * Index buffers correctly. * Matrices correct? */ it->first->render(); } it->first->cleanupAfterRendering(); } geometryPassShader->disable(); glDepthMask(GL_FALSE); glDisable(GL_CULL_FACE); glDisable(GL_DEPTH_TEST); The function in MeshResource that handles setting up the uniforms is as follows: void MeshResource::setupBeforeRendering() { glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glEnableVertexAttribArray(2); glEnableVertexAttribArray(3); glEnableVertexAttribArray(4); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iboID); glBindBuffer(GL_ARRAY_BUFFER, vboID); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0); // Vertex position glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 12); // Vertex normal glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 24); // UV layer 0 glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 32); // Vertex color glVertexAttribPointer(4, 1, GL_UNSIGNED_SHORT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 44); //Material index } The code that renders the object is this: void MeshResource::render() { glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } And the code that cleans up is this: void MeshResource::cleanupAfterRendering() { glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); glDisableVertexAttribArray(2); glDisableVertexAttribArray(3); glDisableVertexAttribArray(4); } The end result of this is that I get a black screen, although the end of my rendering pipeline after the rendering code (essentially just drawing axes and lines on the screen) works properly, so I'm fairly sure it's not an issue with the passing of uniforms. If, however, I change the code slightly so that the rendering code calls the setup immediately before rendering, like so: void MeshResource::render() { setupBeforeRendering(); glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } The program works as desired. I don't want to have to do this, though, as my aim is to set up vertex, material, etc. data once per object type and then render each instance updating only the transformation information. The uniformizeModelMatrix works as follows: void RenderManager::uniformizeModelMatrix(Matrix4 matrix) { glBindBuffer(GL_UNIFORM_BUFFER, globalMatrixUBOID); glBufferSubData(GL_UNIFORM_BUFFER, 0, sizeof(Matrix4), matrix.ptr()); glBindBuffer(GL_UNIFORM_BUFFER, 0); }

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• How to access generic property without knowing the closed generic type

  - by Martin Booka Weser

  I have a generic Type as follows public class TestGeneric<T> { public T Data { get; set; } public TestGeneric(T data) { this.Data = data; } } If i have now an object (which is coming from some external source) from which i know that it's type is of some closed TestGeneric<, but i don't know the TypeParameter T. Now I need to access the Data of my object. Problem is that i can't cast the object, since i don't know exactly to which closed TestGeneric. I use // thx to http://stackoverflow.com/questions/457676/c-reflection-check-if-a-class-is-derived-from-a-generic-class private static bool IsSubclassOfRawGeneric(Type rawGeneric, Type subclass) { while (subclass != typeof(object)) { var cur = subclass.IsGenericType ? subclass.GetGenericTypeDefinition() : subclass; if (rawGeneric == cur) { return true; } subclass = subclass.BaseType; } return false; } to make sure, my object is of the generic type. The code in question is as follows: public static void Main() { object myObject = new TestGeneric<string>("test"); // or from another source if (IsSubclassOfRawGeneric(typeof(TestGeneric<>), myObject.GetType())) { // the following gives an InvalidCastException // var data = ((TestGeneric<object>)myObject).Data; // if i try to access the property with reflection // i get an InvalidOperationException var dataProperty = typeof(TestGeneric<>).GetProperty("Data"); object data = dataProperty.GetValue(myObject, new object[] { }); } } I need the Data regardless of its type (well, if i could ask for its type using GetType() would be fine, but not necessary) since i just want to dump it in xml using ToString(). Any suggestions? Thanx.

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• ERROR! (Using Excel's named ranges from C#)

  - by mcoolbeth

  In the following, I am trying to persist a set of objects in an excel worksheet. Each time the function is called to store a value, it should allocate the next cell of the A column to store that object. However, an exception is thrown by the Interop library on the first call to get_Range(). (right after the catch block) Does anyone know what I am doing wrong? private void AddName(string name, object value) { Excel.Worksheet jresheet; try { jresheet = (Excel.Worksheet)_app.ActiveWorkbook.Sheets["jreTemplates"]; } catch { jresheet = (Excel.Worksheet)_app.ActiveWorkbook.Sheets.Add(Type.Missing, Type.Missing, Type.Missing, Type.Missing); jresheet.Visible = Microsoft.Office.Interop.Excel.XlSheetVisibility.xlSheetVeryHidden; jresheet.Name = "jreTemplates"; jresheet.Names.Add("next", "A1", true, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing); } Excel.Range cell = jresheet.get_Range("next", Type.Missing); cell.Value2 = value; string address = ((Excel.Name)cell.Name).Name; _app.ActiveWorkbook.Names.Add(name, address, false, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing); cell = cell.get_Offset(1, 0); jresheet.Names.Add("next", ((Excel.Name)cell.Name).Name, true, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing); }

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• WordPress contact form email as PDF

  - by lock

  I am using the below code for my WordPress site which is emailing all the form details as an HTML text but I need the details to be written into a PDF first and then have to email the PDF as an attachment. How can I achieve this? This is not a PHP code to use PHP's writePDF modules. So, any idea or any code to implement this? <div style="padding-left: 100px;"> [raw] [contact-form subject="Best Aussie Broker" to="[email protected]"] <div id="main34" style="border: 1px solid black; border-radius: 15px; width: 720px; padding: 15px;"> &nbsp; <h2><span style="color: #ff6600;">Express Application</span></h2> &nbsp; [contact-field label="First Name" type="name" required="true" /] [contact-field label="Last Name" type="text" /] [contact-field label="Email" type="email" required="true" /] [contact-field label="Purpose of Finance?" type="select" options="Home Loan,Refinance,Investment Loan,Debt Consolidation,Other" /] [contact-field label="Your deposit amount" type="text" /] [contact-field label="Amount you need to borrow?" type="text" /] [contact-field label="Brief description of the purpose for finance" type="textarea" required="true" /] <div><label></label> <input class="radio" type="radio" name="19" value="Single Application" onchange="showsingle();" /> <label class="radio">Single Application</label> <div class="clear-form"></div> <input class="radio" type="radio" name="19" value="Joint Application" onchange="showjoint();" /> <label class="radio">Joint Application</label> <div class="clear-form"></div> [contact-field label="Privacy Act" type="checkbox" required="true" /] I have read the Privacy Act 1988 (as Amended) and understand that by selecting the submit button I/we Authorize Best Aussie Broker to act on my/our behalf and manage personal information in relation to this application.<br> <a href="http://googleplex.com.au/pdf.pdf"><img src="http://googleplex.com.au/pdf.png" alt="" /> </a> </div> </div> <div id="single" style="display: none; width: 720px; border: 1px solid black; border-radius: 15px; padding: 15px; margin-top: 10px;"> <div style="padding-top: 10px; width: 720px; text-align: left;"> <h4><span style="color: #ff6600;">Last step then we will get all listed Australian vendors to fight it out for your best deal</span></h4> </div> <div> <label class="select" for="19-date-of-birth">Date of Birth</label> [contact-field label="Day" type="select" options="1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31" /] [contact-field label="Month" type="select" options="January,February,March,April,May,June,July,August,September,October,November,December" /] [contact-field label="Year" type="select" options="2000,1999,1998,1997,1996,1995,1994,1993,1992,1991,1990,1989,1988,1987,1986,1985,1984,1983,1982,1981,1980,1979,1978,197,1976,1975,1974,1973,1972,1971,1970,1969,1968,1967,1966,1965,1964,1963,1962,1961,1960,1959,1958,1957,1956,1955,1954,1953,1952,1951,1950,1949,1948,1947,1946,1945,1944,1943,1942,1941,1940,1939,1938,1937,1936,1935,1934,1933,1932,1931,1930,1929,1928,1927,1926,1925,1924,1923,1922,1921,1920, 1919,1918,1917,1916,1915,1914,1913,1912,1911,1910,1909" /] </div> [contact-field label="Address" type="text" /] [contact-field label="Suburb" type="text" /] [contact-field label="Postcode" type="text" /] <div> [contact-field label="State" type="select" options="VIC,NSW,QLD,SA,WA,TAS,NZ,Other" /] </div> [contact-field label="Best Contact" type="radio" options="Landline,Mobile" /] [contact-field label="Phone Number" type="text" /] [contact-field label="Marital Status" type="select" options="Married,Single,Other" /] [contact-field label="Residential Status" type="select" options="Renting, Home Owned, Home Mortgage, Board, Other" /] [contact-field label="Children/Dependents" type="select" options="0,1,2,3,4,5,6" /] <div></div> [contact-field label="Gross Yearly Income" type="text" /] [contact-field label="Current Employer" type="text" /] <div> <label class="select" for="19-year-of-empl">Time at this employer</label> [contact-field label="Year" type="select" options="0,1,2,3,4,5,6,7,8,9,10,More" /] [contact-field label="Month" type="select" options="0,1,2,3,4,5,6,7,8,9,10,11,12" /] </div> <div style="padding-right: 15px;"></div> </div> <div id="joint" style="display: none; width: 720px; border: 1px solid black; border-radius: 15px; padding: 15px; margin-top: 10px;"> <div style="padding-top: 10px; width: 720px; text-align: left;"> <h4><span style="color: #ff6600;">Last step then we will get all listed Australian vendors to fight it out for your best deal</span></h4> </div> <div style="float: left; width: 320px;"> <div> <label class="select" for="19-date-of-birth1">Date of Birth</label> [contact-field label="Day" type="select" options="1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31" /] [contact-field label="Month" type="select" options="January,February,March,April,May,June,July,August,September,October,November,December" /] [contact-field label="Year" type="select" options="2000,1999,1998,1997,1996,1995,1994,1993,1992,1991,1990,1989,1988,1987,1986,1985,1984,1983,1982,1981,1980,1979,1978,197,1976,1975,1974,1973,1972,1971,1970,1969,1968,1967,1966,1965,1964,1963,1962,1961,1960,1959,1958,1957,1956,1955,1954,1953,1952,1951,1950,1949,1948,1947,1946,1945,1944,1943,1942,1941,1940,1939,1938,1937,1936,1935,1934,1933,1932,1931,1930,1929,1928,1927,1926,1925,1924,1923,1922,1921,1920, 1919,1918,1917,1916,1915,1914,1913,1912,1911,1910,1909" /] </div> [contact-field label="Address" type="text" /] [contact-field label="Suburb" type="text" /] [contact-field label="Postcode" type="text" /] <div> [contact-field label="State" type="select" options="VIC,NSW,QLD,SA,WA,TAS,NZ,Other" /] </div> [contact-field label="Best Contact" type="radio" options="Landline,Mobile" /] [contact-field label="Phone Number" type="text" /] <div></div> <div></div> [contact-field label="Marital Status" type="select" options="Married,Single,Other" /] [contact-field label="Residential Status" type="select" options="Renting, Home Owned, Home Mortgage, Board, Other" /] [contact-field label="Children/Dependents" type="select" options="0,1,2,3,4,5,6" /] <div></div> <div><label class="text" for="netincome">Net Income</label> <input id="netincome" type="text" name="netincome" /> <select id="netincome-dropdown" name="netincome-dropdown"> <option>Monthly</option> <option>Yearly</option> </select></div> [contact-field label="Current Employer" type="text" /] <div> <label class="select" for="19-year-of-empl2">Time at this employer</label> [contact-field label="Year" type="select" options="0,1,2,3,4,5,6,7,8,9,10,More" /] [contact-field label="Month" type="select" options="0,1,2,3,4,5,6,7,8,9,10,11,12" /] </div> </div> <div style="float: right; width: 320px; padding-right: 50px;"> <div> <label class="select" for="19-date-of-birth3">Date of Birth</label> [contact-field label="Day" type="select" options="1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31" /] [contact-field label="Month" type="select" options="January,February,March,April,May,June,July,August,September,October,November,December" /] [contact-field label="Year" type="select" options="2000,1999,1998,1997,1996,1995,1994,1993,1992,1991,1990,1989,1988,1987,1986,1985,1984,1983,1982,1981,1980,1979,1978,197,1976,1975,1974,1973,1972,1971,1970,1969,1968,1967,1966,1965,1964,1963,1962,1961,1960,1959,1958,1957,1956,1955,1954,1953,1952,1951,1950,1949,1948,1947,1946,1945,1944,1943,1942,1941,1940,1939,1938,1937,1936,1935,1934,1933,1932,1931,1930,1929,1928,1927,1926,1925,1924,1923,1922,1921,1920, 1919,1918,1917,1916,1915,1914,1913,1912,1911,1910,1909" /] </div> [contact-field label="Address" type="text" /] [contact-field label="Suburb" type="text" /] [contact-field label="Postcode" type="text" /] <div> [contact-field label="State" type="select" options="VIC,NSW,QLD,SA,WA,TAS,NZ,Other" /] </div> [contact-field label="Best Contact" type="radio" options="Landline,Mobile" /] [contact-field label="Phone Number" type="text" /] <div></div> <div></div> [contact-field label="Marital Status" type="select" options="Married,Single,Other" /] [contact-field label="Residential Status" type="select" options="Renting, Home Owned, Home Mortgage, Board, Other" /] [contact-field label="Children/Dependents" type="select" options="0,1,2,3,4,5,6" /] <div></div> <div><label class="text" for="netincome">Net Income</label> <input id="netincome" type="text" name="netincome" /> <select id="netincome-dropdown" name="netincome-dropdown"> <option>Monthly</option> <option>Yearly</option> </select></div> [contact-field label="Current Employer" type="text" /] <div> <label class="select" for="19-year-of-empl">Time at this employer</label> [contact-field label="Year" type="select" options="0,1,2,3,4,5,6,7,8,9,10,More" /] [contact-field label="Month" type="select" options="0,1,2,3,4,5,6,7,8,9,10,11,12" /] </div> </div> <div style="clear: both;"></div> <div></div> </div> &nbsp; [/contact-form][/raw] </div>

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• WCF: collection proxy type on client

  - by Unholy

  I have the following type in wsdl (it is generated by third party tool): <xsd:complexType name="IntArray"> <xsd:sequence> <xsd:element maxOccurs="unbounded" minOccurs="0" name="Elements" type="xsd:int" /> </xsd:sequence> </xsd:complexType> Sometimes Visual Studio generates: public class IntArray : System.Collections.Generic.List<int> {} And sometimes it doesn't generate any proxy type for this wsdl and just uses int[]. Collection type in Web Service configuration is System.Array. What could be the reason for such upredictable behavior? Edited: I found the way how I can reproduce this behavior. For examle we have two types: <xsd:complexType name="IntArray"> <xsd:sequence> <xsd:element maxOccurs="unbounded" minOccurs="0" name="Elements" type="xsd:int" /> </xsd:sequence> </xsd:complexType> <xsd:complexType name="StringArray"> <xsd:sequence> <xsd:element maxOccurs="unbounded" minOccurs="0" name="Elements" type="xsd:string" /> </xsd:sequence> </xsd:complexType> VS generates: public class IntArray : System.Collections.Generic.List<int> {} public class StringArray : System.Collections.Generic.List<string> {} Now I change StringArray type: <xsd:complexType name="StringArray"> <xsd:sequence> <xsd:element maxOccurs="unbounded" minOccurs="0" name="Elements" type="xsd:string" /> <xsd:any minOccurs="0" maxOccurs="unbounded" namespace="##any" processContents="lax" /> </xsd:sequence> <xsd:anyAttribute namespace="##any" processContents="lax"/> </xsd:complexType> VS generates proxy type for StringArray only. But not for IntArray.

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• Get type of the parameter from list of objects, templates, C++

  - by CrocodileDundee

  This question follows to my previous question Get type of the parameter, templates, C++ There is the following data structure: Object1.h template <class T> class Object1 { private: T a1; T a2; public: T getA1() {return a1;} typedef T type; }; Object2.h template <class T> class Object2: public Object1 <T> { private: T b1; T b2; public: T getB1() {return b1;} } List.h template <typename Item> struct TList { typedef std::vector <Item> Type; }; template <typename Item> class List { private: typename TList <Item>::Type items; }; Is there any way how to get type T of an object from the list of objects (i.e. Object is not a direct parameter of the function but a template parameter)? template <class Object> void process (List <Object> *objects) { typename Object::type a1 = objects[0].getA1(); // g++ error: 'Object1<double>*' is not a class, struct, or union type } But his construction works (i.e. Object represents a parameter of the function) template <class Object> void process (Object *o1) { typename Object::type a1 = o1.getA1(); // OK }

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• Template specialization to use default type if class member typedef does not exist

  - by Frank

  Hi Everyone, I'm trying to write code that uses a member typedef of a template argument, but want to supply a default type if the template argument does not have that typedef. A simplified example I've tried is this: struct DefaultType { DefaultType() { printf("Default "); } }; struct NonDefaultType { NonDefaultType() { printf("NonDefault "); } }; struct A {}; struct B { typedef NonDefaultType Type; }; template<typename T, typename Enable = void> struct Get_Type { typedef DefaultType Type; }; template<typename T> struct Get_Type< T, typename T::Type > { typedef typename T::Type Type; }; int main() { Get_Type::Type test1; Get_Type::Type test2; } I would expect this to print "Default NonDefault", but instead it prints "Default Default". My expectation is that the second line in main() should match the specialized version of Get_Type, because B::Type exists. However, this does not happen. Can anyone explain what's going on here and how to fix it, or another way to accomplish the same goal? Thank you.

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• With NHibernate, how can I add a child object when updating a parent object?

  - by BMZ

  I have a simple Parent/Child relationship between a Person object and an Address object. The Person object exists in the DB. After doing a Get on the Person, I add a new Address object to the Address sub-object list of the parent, and do some other updates to the Person object. Finally, I do an Update on the Person object. With a SQL trace window, I can see the update to the Person object to the Person table and the Insert of the Address record to the Address table. The issue is that, after the update is performed, the AddressId (primary key on the Address object) is still set to 0, which is what it defaults to when you first initialize the Address object. I have verified that when I do an Add, this value is set correctly. Is this a known issue when trying to add sub-objects as part of an NHibernate UPDATE? Sample code and mapping files are below Thanks <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"> <class name="BusinessEntities.Wellness.Person,BusinessEntities.Wellness" table="Person" lazy="true" dynamic-insert="true" dynamic-update="false"> <id name="Personid" column="PersonID" type="int"> <generator class="native" /> </id> <version type="binary" generated="always" name="RecordVersion" column="`RecordVersion`"/> <property type="int" not-null="true" name="Customerid" column="`CustomerID`" /> <property type="AnsiString" not-null="true" length="9" name="Ssn" column="`SSN`" /> <property type="AnsiString" not-null="true" length="30" name="FirstName" column="`FirstName`" /> <property type="AnsiString" not-null="true" length="35" name="LastName" column="`LastName`" /> <property type="AnsiString" length="1" name="MiddleInitial" column="`MiddleInitial`" /> <property type="DateTime" name="DateOfBirth" column="`DateOfBirth`" /> <bag name="PersonAddresses" inverse="true" lazy="true" cascade="all"> <key column="PersonID" /> <one-to-many class="BusinessEntities.Wellness.PersonAddress,BusinessEntities.Wellness" / </bag> </class> </hibernate-mapping> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"> <class name="BusinessEntities.Wellness.PersonAddress,BusinessEntities.Wellness" table="PersonAddress" lazy="true" dynamic-insert="true" dynamic-update="false"> <id name="PersonAddressId" column="PersonAddressID" type="int"> <generator class="native" /> </id> <version type="binary" generated="always" name="RecordVersion" column="`RecordVersion`" /> <property type="AnsiString" not-null="true" length="1" name="AddressTypeid" column="`AddressTypeID`" /> <property type="AnsiString" not-null="true" length="60" name="AddressLine1" column="`AddressLine1`" /> <property type="AnsiString" length="60" name="AddressLine2" column="`AddressLine2`" /> <property type="AnsiString" length="60" name="City" column="`City`" /> <property type="AnsiString" length="2" name="UsStateId" column="`USStateID`" /> <property type="AnsiString" length="5" name="UsPostalCodeId" column="`USPostalCodeID`" /> <many-to-one name="Person" cascade="none" column="PersonID" /> </class> </hibernate-mapping> Person newPerson = new Person(); newPerson.PersonName = "John Doe"; newPerson.SSN = "111111111"; newPerson.CreatedBy = "RJC"; newPerson.CreatedDate = DateTime.Today; personDao.AddPerson(newPerson); Person updatePerson = personDao.GetPerson(newPerson.PersonId); updatePerson.PersonAddresses = new List<PersonAddress>(); PersonAddress addr = new PersonAddress(); addr.AddressLine1 = "1 Main St"; addr.City = "Boston"; addr.State = "MA"; addr.Zip = "12345"; updatePerson.PersonAddresses.Add(addr); personDao.UpdatePerson(updatePerson); int addressID = updatePerson.PersonAddresses[0].AddressId;

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• Design suggestions needed to create a MathBuilder framework

  - by Darf Zon

  Let explain what I'm trying to create. I'm creating a framework, the idea is to provide base classes to generate a math problem. Why do I need this framework? Because at first time, I realized when I create a new math problem I always do the same steps. Configuration settings such range numbers. For example if I'm developing multiplications, in beginner level only generate the first number between 2-5 or in advanced level, the first number will be between 6- 9, for example. Generate problem method. All the time I need to invoke a method like this to generate the problem. This one receives the configuration settings and generate the number according to them. And generate the object with the respective data. Validate the problem. Sometimes the problem generated is not valid. For example, supposed I'm creating fractions in most simplified, if I receive 2/4, the program should detect that this is not valid and must generate another like this one, 1/4. Load the view. All of them, have a custom view (please watch below the images). All of the problems must know how to CHECK if the user result is correct. All of this problems has answers. Some of them just require one answer, anothers may require more than one, so I guess a way to maintain flexibility to the developer has all the answers he wanna used. At the beginning I started using PRISM. Generate modules for each math problem was the idea and load it in the main system. I guess are the most important things of this idea. Let me showing some problems which I create in a WPF standalone program. Here I have a math problem about areas. When I generate the problem a set to the view the object and it draw it. In beginner level, I set in the configuration settings that just load square types. But in advance level, can load triangles and squares randomly. In this another, generate a binary problem like addition, subtraction, multiplication or division. Above just generate a single problem. The idea of this is to show a test o quiz, I mean get a worksheet (this I call as a collection of problems) where the user can answer it. I hope gets the idea with my ugly drawing. How to load this math problems? As I said above, I started using PRISM, and each module contains a math problem kind. This is a snapshot of my first demo. Below show the modules loaded, and center the respective configurations or levels. Until momment, I have no idea to start creating this software. I just know that I need a question | problem class, response class, user class. But I get lost about what properties should have to contain in it. Please give a little hand of this framework. I put much effort on this question, so if any isn't clear, let me know to clarify it.

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• Starting to create a MathBuilder framework, help to start creating the design

  - by Darf Zon

  Let explain what I'm trying to create. I'm creating a framework, the idea is to provide base classes to generate a math problem. Why do I need this framework? Because at first time, I realized when I create a new math problem I always do the same steps. Configuration settings such range numbers. For example if I'm developing multiplications, in beginner level only generate the first number between 2-5 or in advanced level, the first number will be between 6- 9, for example. Generate problem method. All the time I need to invoke a method like this to generate the problem. This one receives the configuration settings and generate the number according to them. And generate the object with the respective data. Validate the problem. Sometimes the problem generated is not valid. For example, supposed I'm creating fractions in most simplified, if I receive 2/4, the program should detect that this is not valid and must generate another like this one, 1/4. Load the view. All of them, have a custom view (please watch below the images). All of the problems must know how to CHECK if the user result is correct. All of this problems has answers. Some of them just require one answer, anothers may require more than one, so I guess a way to maintain flexibility to the developer has all the answers he wanna used. At the beginning I started using PRISM. Generate modules for each math problem was the idea and load it in the main system. I guess are the most important things of this idea. Let me showing some problems which I create in a WPF standalone program. Here I have a math problem about areas. When I generate the problem a set to the view the object and it draw it. In beginner level, I set in the configuration settings that just load square types. But in advance level, can load triangles and squares randomly. In this another, generate a binary problem like addition, subtraction, multiplication or division. Above just generate a single problem. The idea of this is to show a test o quiz, I mean get a worksheet (this I call as a collection of problems) where the user can answer it. I hope gets the idea with my ugly drawing. How to load this math problems? As I said above, I started using PRISM, and each module contains a math problem kind. This is a snapshot of my first demo. Below show the modules loaded, and center the respective configurations or levels. Until momment, I have no idea to start creating this software. I just know that I need a question | problem class, response class, user class. But I get lost about what properties should have to contain in it. Please give a little hand of this framework. I put much effort on this question, so if any isn't clear, let me know to clarify it.

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• Why is there no service-oriented language?

  - by Wolfgang

  Edit: To avoid further confusion: I am not talking about web services and such. I am talking about structuring applications internally, it's not about how computers communicate. It's about programming languages, compilers and how the imperative programming paradigm is extended. Original: In the imperative programming field, we saw two paradigms in the past 20 years (or more): object-oriented (OO), and service-oriented (SO) aka. component-based (CB). Both paradigms extend the imperative programming paradigm by introducing their own notion of modules. OO calls them objects (and classes) and lets them encapsulates both data (fields) and procedures (methods) together. SO, in contrast, separates data (records, beans, ...) from code (components, services). However, only OO has programming languages which natively support its paradigm: Smalltalk, C++, Java and all other JVM-compatibles, C# and all other .NET-compatibles, Python etc. SO has no such native language. It only comes into existence on top of procedural languages or OO languages: COM/DCOM (binary, C, C++), CORBA, EJB, Spring, Guice (all Java), ... These SO frameworks clearly suffer from the missing native language support of their concepts. They start using OO classes to represent services and records. This leads to designs where there is a clear distinction between classes that have methods only (services) and those that have fields only (records). Inheritance between services or records is then simulated by inheritance of classes. Technically, its not kept so strictly but in general programmers are adviced to make classes to play only one of the two roles. They use additional, external languages to represent the missing parts: IDL's, XML configurations, Annotations in Java code, or even embedded DSL like in Guice. This is especially needed, but not limited to, since the composition of services is not part of the service code itself. In OO, objects create other objects so there is no need for such facilities but for SO there is because services don't instantiate or configure other services. They establish an inner-platform effect on top of OO (early EJB, CORBA) where the programmer has to write all the code that is needed to "drive" SO. Classes represent only a part of the nature of a service and lots of classes have to be written to form a service together. All that boiler plate is necessary because there is no SO compiler which would do it for the programmer. This is just like some people did it in C for OO when there was no C++. You just pass the record which holds the data of the object as a first parameter to the procedure which is the method. In a OO language this parameter is implicit and the compiler produces all the code that we need for virtual functions etc. For SO, this is clearly missing. Especially the newer frameworks extensively use AOP or introspection to add the missing parts to a OO language. This doesn't bring the necessary language expressiveness but avoids the boiler platform code described in the previous point. Some frameworks use code generation to produce the boiler plate code. Configuration files in XML or annotations in OO code is the source of information for this. Not all of the phenomena that I mentioned above can be attributed to SO but I hope it clearly shows that there is a need for a SO language. Since this paradigm is so popular: why isn't there one? Or maybe there are some academic ones but at least the industry doesn't use one.

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• What are the disadvantages of self-encapsulation?

  - by Dave Jarvis

  Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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• Is my class structure good enough?

  - by Rivten

  So I wanted to try out this challenge on reddit which is mostly about how you structure your data the best you can. I decided to challenge my C++ skills. Here's how I planned this. First, there's the Game class. It deals with time and is the only class main has access to. A game has a Forest. For now, this class does not have a lot of things, only a size and a Factory. Will be put in better use when it will come to SDL-stuff I guess A Factory is the thing that deals with the Game Objects (a.k.a. Trees, Lumberjack and Bears). It has a vector of all GameObjects and a queue of Events which will be managed at the end of one month. A GameObject is an abstract class which can be updated and which can notify the Event Listener The EventListener is a class which handles all the Events of a simulation. It can recieve events from a Game Object and notify the Factory if needed, the latter will manage correctly the event. So, the Tree, Lumberjack and Bear classes all inherits from GameObject. And Sapling and Elder Tree inherits from Tree. Finally, an Event is defined by an event_type enumeration (LUMBERJACK_MAWED, SAPPLING_EVOLUTION, ...) and an event_protagonists union (a GameObject or a pair of GameObject (who killed who ?)). I was quite happy at first with this because it seems quite logic and flexible. But I ended up questionning this structure. Here's why : I dislike the fact that a GameObject need to know about the Factory. Indeed, when a Bear moves somewhere, it needs to know if there's a Lumberjack ! Or it is the Factory which handles places and objects. It would be great if a GameObject could only interact with the EventListener... or maybe it's not that much of a big deal. Wouldn't it be better if I separate the Factory in three vectors ? One for each kind of GameObject. The idea would be to optimize research. If I'm looking do delete a dead lumberjack, I would only have to look in one shorter vector rather than a very long vector. Another problem arises when I want to know if there is any particular object in a given case because I have to look for all the gameObjects and see if they are at the given case. I would tend to think that the other idea would be to use a matrix but then the issue would be that I would have empty cases (and therefore unused space). I don't really know if Sapling and Elder Tree should inherit from Tree. Indeed, a Sapling is a Tree but what about its evolution ? Should I just delete the sapling and say to the factory to create a new Tree at the exact same place ? It doesn't seem natural to me to do so. How could I improve this ? Is the design of an Event quite good ? I've never used unions before in C++ but I didn't have any other ideas about what to use. Well, I hope I have been clear enough. Thank you for taking the time to help me !

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• Java Generics Type Safety warning with recursive Hashmap

  - by GC

  Hi, I'm using a recursive tree of hashmaps, specifically Hashmap map where Object is a reference to another Hashmap and so on. This will be passed around a recursive algorithm: foo(String filename, Hashmap<String, Object> map) { //some stuff here for (Entry<String, Object> entry : map.entrySet()) { //type warning that must be suppressed foo(entry.getKey(), (HashMap<String, Object>)entry.getValue()); } } I know for sure Object is of type Hashmap<String, Object> but am irritated that I have to suppress the warning using @SuppressWarnings("unchecked"). I'll be satisfied with a solution that does either a assert(/*entry.getValue() is of type HashMap<String, Object>*/) or throws an exception when it isn't. I went down the Generics route for compile type safety and if I suppress the warning then it defeats the purpose. Thank you for your comments, ksb

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• Java generic return type

  - by Colby77

  Hi, I'd like to write a method that can accept a type param (or whatever the method can figure out the type from) and return a value of this type so I don't have to cast the return type. Here is a method: public Object doIt(Object param){ if(param instanceof String){ return "string"; }else if(param instanceof Integer){ return 1; }else{ return null; } } When I call this method, and pass in it a String, even if I know the return type will be a String I have to cast the return Object. This is similar to the int param. How shall I write this method to accept a type param, and return this type?

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• jQuery plugin, return value from function

  - by Marius

  Hello there, Markup: <input type="text" name="email" /> Code: $(':text').focusout(function(){ $(this).validate(function(){ $(this).attr('name'); }); }); Plugin: (function($){ $.fn.validate = function(type) { return this.each(function(type) { if (type == 'email') { matches = this.val().match('/.+@.+\..{2,7}/'); (matches != null) ? alert('valid') : alert('invalid'); } /*else if (type == 'name') { } else if (type == 'age') { } else if (type == 'text') { }*/ else { alert('total failure'); } }); }; })(jQuery); The problem is that when I execute the code above, it runs the plugin as if type was a string: "function(){ $(this).attr('name'); });" instead of executing it as a function. How do I solve this? Thank you for your time. Kind regards, Marius

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