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• What are the benefits of a classical structure over a prototyple one?

  - by Rixius

  I have only recently started programming significantly, and being completely self-taught, I unfortunately don't have the benefits of a detailed Computer science course. I've been reading a lot about JavaScript lately, and I'm trying to find the benefit in classes over the prototype nature of JavaScript. The question seems to be drawn down the middle of which one is better, and I want to see the classical side of it. When I look at the prototype example: var inst_a = { "X": 123, "Y": 321, add: function () { return this.X+this.Y; } }; document.write(inst_a.add()); And then the classical version function A(x,y){ this.X = x; this.Y = y; this.add = function(){ return this.X+this.Y; }; }; var inst_a = new A(123,321); document.write(inst_a.add()); I begun thinking about this because I'm looking at the new ecmascript revision 5 and a lot of people seem up in arms that they didn't add a Class system.

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• Problem with inherited classes in C#

  - by Unniloct

  I have a class called "Entity," with two child classes: "Creature" and "Item." (I'm making a game.) Creature has two functions called "Attack," one for attacking Creatures, and one for attacking Items. So far, everything works well. Now I'm working on the shooting bit, so I have a function called SelectTarget(). It takes all of the Entities (both Creatures and Items) in the player's view that the player can shoot and lets the player choose one. So here lies the problem: SelectTarget() returns an Entity, but I need some code to figure out whether that Entity is a Creature or an Item, and process it appropriately. Since this question looks kind of empty without any code, and I'm not 100% sure my explanation is good enough, here's where I'm at: if (Input.Check(Key.Fire)) { Entity target = Game.State.SelectTarget.Run(); this.Draw(); if (target != null) { //Player.Attack(target); // This won't work, because I have: // Player.Attack((Creature)Target) // Player.Attack((Item)Target) // but nothing for Entity, the parent class to Creature and Item. return true; } } (If the way the game is laid out seems weird, it's a roguelike.)

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• Trying to instantiate a class member in C++ with a variable name

  - by MarcZero

  Hello. I am writing a program for class that is asking us to create a class of "book". We are then supposed to create new instantiations of that class upon demand from the user. I am new to C++ so I am attempting to code this out but am running into a problem. The main problem is how do I instantiate a class with a variable if I don't know how many I will have to do ahead of time. The user could ask to add 1 book or 1000. I am looking at this basic code: This is the simple code I started with. I wanted to have an index int keep a number and have the book class I create be called by that int (0, 1, 2, etc...) So I attempted to convert the incoming index int into a string, but I'm kind of stuck from here. void addBook(int index){ string bookName; std::stringstream ss; ss << index; book bookName; cout << "Enter the Books Title: "; cin >> bookName.title; } But obviously this doesn't work as "bookName" is a string to the computer and not the class member I tried to create. All of the tutorials I have seen online and in my text show the classes being instantiated with names in the code, but I just don't know how to make it variable so I can create any amount of "books" that the user might want. Any insight on this would be appreciated. Thank you for your time.

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• Manipulate method functionality call

  - by danrichardson

  Hello, is it possibly in c# to have some sort of base class functionality which is manipulated slightly based on the class. For instance say i have the following code (which will quite obviously not compile it's meant to only be for demonstrative purposes) class BaseFunctionality { public virtual bool adminCall public static string MethodName(int id, string parameter) { if (adminCall) return dbcall.Execute(); else return dbcall.ExecuteMe(); } } class Admin : BaseFunctionality { override bool adminCall = true; } class Front : BaseFunctionality { override bool adminCall = false; } Now what i would like to be able to do is; string AdminCall = Admin.MethodName(1, "foo"); string FrontCall = Front.MethodName(2, "bar"); Is their any way to do something like this? I'm trying to do everything with static methods so i do not have to instantiate classes all the time, and have nice clean code which is only being manipulated in one place. The idea behind this is so that there is minimal code repeating and makes things easier to expand on, so for instance another class could implement the BaseFunctionality later on. Thanks Dan

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• Jquery Selecting Multiple Classes, Loading External Files

  - by WillingLearner

  I have 2 links, with the class dynamicLoad. <ul class="navbar"> <li><a href="Page3-News.html" class="dynamicLoad news">NEWS</a></li> <li><a href="Page2-Events.html" class="dynamicLoad">EVENTS</a></li> </ul> and then I have this already working code, which loads external pages into a div named #MainWrapper: <script type="text/javascript"> $( document ).ready( function() { $( 'a.dynamicLoad' ).click( function( e ) { e.preventDefault(); // prevent the browser from following the link e.stopPropagation(); // prevent the browser from following the link $( '#MainWrapper' ).load( $( this ).attr( 'href' ) ); }); }); </script> How do I edit this code and my links, so that i can target the 1st link with the classes of both dynamicLoad and news, and then, load another script and/or pages into the main wrapper, without breaking its already working functionality?

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• Memory Leak Issue in Weblogic, SUN, Apache and Oracle classes Options

  - by Amit

  Hi All, Please find below the description of memory leaks issues. Statistics show major growth in the perm area (static classes). Flows were ran for 8 hours , Heap dump was taken after 2 hours and at the end. A growth in Perm area was identified Statistics show from our last run 240MB growth in 6 hour,40mb growth every hour 2GB heap –can hold ¾ days ,heap will be full in ¾ days Heap dump show –growth in area as mentioned below JMS connection/session Area Apache org.apache.xml.dtm.DTM[] org.apache.xml.dtm.ref.ExpandedNameTable$ExtendedType org.jdom.AttributeList org.jdom.Content[] org.jdom.ContentList org.jdom.Element SUN * ConstantPoolCacheKlass * ConstantPoolKlass * ConstMethodKlass * MethodDataKlass * MethodKlass * SymbolKlass byte[] char[] com.sun.org.apache.xml.internal.dtm.DTM[] com.sun.org.apache.xml.internal.dtm.ref.ExtendedType java.beans.PropertyDescriptor java.lang.Class java.lang.Long java.lang.ref.WeakReference java.lang.ref.SoftReference java.lang.String java.text.Format[] java.util.concurrent.ConcurrentHashMap$Segment java.util.LinkedList$Entry Weblogic com.bea.console.cvo.ConsoleValueObject$PropertyInfo com.bea.jsptools.tree.TreeNode com.bea.netuix.servlets.controls.content.StrutsContent com.bea.netuix.servlets.controls.layout.FlowLayout com.bea.netuix.servlets.controls.layout.GridLayout com.bea.netuix.servlets.controls.layout.Placeholder com.bea.netuix.servlets.controls.page.Book com.bea.netuix.servlets.controls.window.Window[] com.bea.netuix.servlets.controls.window.WindowMode javax.management.modelmbean.ModelMBeanAttributeInfo weblogic.apache.xerces.parsers.SecurityConfiguration weblogic.apache.xerces.util.AugmentationsImpl weblogic.apache.xerces.util.AugmentationsImpl$SmallContainer weblogic.apache.xerces.util.SymbolTable$Entry weblogic.apache.xerces.util.XMLAttributesImpl$Attribute weblogic.apache.xerces.xni.QName weblogic.apache.xerces.xni.QName[] weblogic.ejb.container.cache.CacheKey weblogic.ejb20.manager.SimpleKey weblogic.jdbc.common.internal.ConnectionEnv weblogic.jdbc.common.internal.StatementCacheKey weblogic.jms.common.Item weblogic.jms.common.JMSID weblogic.jms.frontend.FEConnection weblogic.logging.MessageLogger$1 weblogic.logging.WLLogRecord weblogic.rjvm.BubblingAbbrever$BubblingAbbreverEntry weblogic.rjvm.ClassTableEntry weblogic.rjvm.JVMID weblogic.rmi.cluster.ClusterableRemoteRef weblogic.rmi.internal.CollocatedRemoteRef weblogic.rmi.internal.PhantomRef weblogic.rmi.spi.ServiceContext[] weblogic.security.acl.internal.AuthenticatedSubject weblogic.security.acl.internal.AuthenticatedSubject$SealableSet weblogic.servlet.internal.ServletRuntimeMBeanImpl weblogic.transaction.internal.XidImpl weblogic.utils.collections.ConcurrentHashMap$Entry Oracle XA Transaction oracle.jdbc.driver.Binder[] oracle.jdbc.driver.OracleDatabaseMetaData oracle.jdbc.driver.T4C7Ocommoncall oracle.jdbc.driver.T4C7Oversion oracle.jdbc.driver.T4C8Oall oracle.jdbc.driver.T4C8Oclose oracle.jdbc.driver.T4C8TTIBfile oracle.jdbc.driver.T4C8TTIBlob oracle.jdbc.driver.T4C8TTIClob oracle.jdbc.driver.T4C8TTIdty oracle.jdbc.driver.T4C8TTILobd oracle.jdbc.driver.T4C8TTIpro oracle.jdbc.driver.T4C8TTIrxh oracle.jdbc.driver.T4C8TTIuds oracle.jdbc.driver.T4CCallableStatement oracle.jdbc.driver.T4CClobAccessor oracle.jdbc.driver.T4CConnection oracle.jdbc.driver.T4CMAREngine oracle.jdbc.driver.T4CNumberAccessor oracle.jdbc.driver.T4CPreparedStatement oracle.jdbc.driver.T4CTTIdcb oracle.jdbc.driver.T4CTTIk2rpc oracle.jdbc.driver.T4CTTIoac oracle.jdbc.driver.T4CTTIoac[] oracle.jdbc.driver.T4CTTIoauthenticate oracle.jdbc.driver.T4CTTIokeyval oracle.jdbc.driver.T4CTTIoscid oracle.jdbc.driver.T4CTTIoses oracle.jdbc.driver.T4CTTIOtxen oracle.jdbc.driver.T4CTTIOtxse oracle.jdbc.driver.T4CTTIsto oracle.jdbc.driver.T4CXAConnection oracle.jdbc.driver.T4CXAResource oracle.jdbc.oracore.OracleTypeADT[] oracle.jdbc.xa.OracleXAResource$XidListEntry oracle.net.ano.Ano oracle.net.ns.ClientProfile oracle.net.ns.ClientProfile oracle.net.ns.NetInputStream oracle.net.ns.NetOutputStream oracle.net.ns.SessionAtts oracle.net.nt.ConnOption oracle.net.nt.ConnStrategy oracle.net.resolver.AddrResolution oracle.sql.CharacterSet1Byte we are using Oracle BEA Weblogic 9.2 MP3 JDK 1.5.12 Oracle versoin 10.2.0.4 (for oracle we found one path which is needed to applied to avoid XA transaction memory leaks). But we are stuck to resolve SUN, BEA Weblgogic and Apache leaks. please suggest... regards, Amit J.

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• C++ visibility of privately inherited typedefs to nested classes

  - by beldaz

  First time on StackOverflow, so please be tolerant. In the following example (apologies for the length) I have tried to isolate some unexpected behaviour I've encountered when using nested classes within a class that privately inherits from another. I've often seen statements to the effect that there is nothing special about a nested class compared to an unnested class, but in this example one can see that a nested class (at least according to GCC 4.4) can see the public typedefs of a class that is privately inherited by the closing class. I appreciate that typdefs are not the same as member data, but I found this behaviour surprising, and I imagine many others would, too. So my question is threefold: Is this standard behaviour? (a decent explanation of why would be very helpful) Can one expect it to work on most modern compilers (i.e., how portable is it)? #include <iostream> class Base { typedef int priv_t; priv_t priv; public: typedef int pub_t; pub_t pub; Base() : priv(0), pub(1) {} }; class PubDerived : public Base { public: // Not allowed since Base::priv is private // void foo() {std::cout << priv << "\n";} class Nested { // Not allowed since Nested has no access to PubDerived member data // void foo() {std::cout << pub << "\n";} // Not allowed since typedef Base::priv_t is private // void bar() {priv_t x=0; std::cout << x << "\n";} }; }; class PrivDerived : private Base { public: // Allowed since Base::pub is public void foo() {std::cout << pub << "\n";} class Nested { public: // Works (gcc 4.4 - see below) void fred() {pub_t x=0; std::cout << x << "\n";} }; }; int main() { // Not allowed since typedef Base::priv_t private // std::cout << PubDerived::priv_t(0) << "\n"; // Allowed since typedef Base::pub_t is inaccessible std::cout << PubDerived::pub_t(0) << "\n"; // Prints 0 // Not allowed since typedef Base::pub_t is inaccessible //std::cout << PrivDerived::pub_t(0) << "\n"; // Works (gcc 4.4) PrivDerived::Nested o; o.fred(); // Prints 0 return 0; }

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• C++ classes & linked list: adding & counting items

  - by user342289

  I need to make a linked list with classes. Each list will store two values: a URI and IP. After doing all the adding, I need to be able count the total number of items in the linked list. I have tried the following code but it doesn't compile. Any suggestions please? #include <iostream> #include <cstdlib> #include <string> using namespace std; class ip_uri_store { protected: string ip; string uri; ip_uri_store *next; public: ip_uri_store(string huri, string hip); void additem(string auri, string aip); void deleteitem(string duri); void findbyuri(string furi); void findbyip(string fip); int totalitems(); }; ip_uri_store *head = NULL; ip_uri_store *curr = NULL; void ip_uri_store::additem(string auri, string aip) { curr = head; while (curr->next != NULL) { curr = curr->next; } curr->uri = auri; curr->next = new ip_uri_store; curr->ip = aip; curr->next = new ip_uri_store; curr = curr->next; curr = head; } int ip_uri_store::totalitems() { int i = 0; curr = head; while (curr->next != NULL) { i += 1; curr = curr->next; } return i; } int main(int argc, char *argv[]) { if (argc == 1) { cout << "123456, [email protected], Gordon Brown" << endl; return (0); } head = new ip_uri_store; curr = head; int i; for (i = 1; i < argc; i++) { if (argv[i][0] == 'A') //add item { ip_uri_store.additem(argv[i + 1], argv[i + 2]); i += 2; } else if (argv[i][0] == 'N') //print total tiems { cout << ip_uri_store.totalitems() << endl; } else { cout << "command error\n"; return 0; } } return (0); }

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• How to use objetcs as modules/functors in Scala?

  - by Jeff

  Hi. I want to use object instances as modules/functors, more or less as shown below: abstract class Lattice[E] extends Set[E] { val minimum: E val maximum: E def meet(x: E, y: E): E def join(x: E, y: E): E def neg(x: E): E } class Calculus[E](val lat: Lattice[E]) { abstract class Expr case class Var(name: String) extends Expr {...} case class Val(value: E) extends Expr {...} case class Neg(e1: Expr) extends Expr {...} case class Cnj(e1: Expr, e2: Expr) extends Expr {...} case class Dsj(e1: Expr, e2: Expr) extends Expr {...} } So that I can create a different calculus instance for each lattice (the operations I will perform need the information of which are the maximum and minimum values of the lattice). I want to be able to mix expressions of the same calculus but not be allowed to mix expressions of different ones. So far, so good. I can create my calculus instances, but problem is that I can not write functions in other classes that manipulate them. For example, I am trying to create a parser to read expressions from a file and return them; I also was trying to write an random expression generator to use in my tests with ScalaCheck. Turns out that every time a function generates an Expr object I can't use it outside the function. Even if I create the Calculus instance and pass it as an argument to the function that will in turn generate the Expr objects, the return of the function is not recognized as being of the same type of the objects created outside the function. Maybe my english is not clear enough, let me try a toy example of what I would like to do (not the real ScalaCheck generator, but close enough). def genRndExpr[E](c: Calculus[E], level: Int): Calculus[E]#Expr = { if (level > MAX_LEVEL) { val select = util.Random.nextInt(2) select match { case 0 => genRndVar(c) case 1 => genRndVal(c) } } else { val select = util.Random.nextInt(3) select match { case 0 => new c.Neg(genRndExpr(c, level+1)) case 1 => new c.Dsj(genRndExpr(c, level+1), genRndExpr(c, level+1)) case 2 => new c.Cnj(genRndExpr(c, level+1), genRndExpr(c, level+1)) } } } Now, if I try to compile the above code I get lots of error: type mismatch; found : plg.mvfml.Calculus[E]#Expr required: c.Expr case 0 = new c.Neg(genRndExpr(c, level+1)) And the same happens if I try to do something like: val boolCalc = new Calculus(Bool) val e1: boolCalc.Expr = genRndExpr(boolCalc) Please note that the generator itself is not of concern, but I will need to do similar things (i.e. create and manipulate calculus instance expressions) a lot on the rest of the system. Am I doing something wrong? Is it possible to do what I want to do? Help on this matter is highly needed and appreciated. Thanks a lot in advance.

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• jQuery: How to find and change multiply th classes between n & n

  - by Ravex

  Hi everyone. I have some table structure: <tr class="row-2"><tr> <tr class="row-3">..<tr> <tr class="row-4">..<tr> <tr class="row-5">..<tr> <tr class="row-6">..<tr> <tr class="row-7"><tr> <tr class="row-8">..<tr> <tr class="row-9">..<tr> <tr class="row-10">..<tr> <tr class="row-11">..<tr> ...etc for this example TR with classes "row-2" and "row-7" is parrent product link wich expand child rows. <script> $(function() { $('tr.parent') .css("cursor","pointer") .css("color","red") .attr("title","Click to expand/collapse") .click(function(){ $(this).siblings('.child-'+this.id).toggle(); }); $('tr[@class^=child-]').hide().children('td'); }); </script> Rows -3...-6 is child of row-2 and Rows -8...-11 is child of row-7 How i can find row-2, row-7, etc then add second class "parrent" and ID similar class (id="row-2", id="row-7", etc)? Also i need add in each TR between row-2 and row-7 class equal previous parrent row. In bottom line i need something like this: <tr class="row-2 parrent" id="row-2"><tr> <tr class="row-3 child-row2">..<tr> <tr class="row-4 child-row2">..<tr> <tr class="row-5 child-row2">..<tr> <tr class="row-6 child-row2">..<tr> <tr class="row-7 parrent" id="row-7"><tr> <tr class="row-8 child-row7">..<tr> <tr class="row-9 child-row7">..<tr> <tr class="row-10 child-row7">..<tr> <tr class="row-11 child-row7">..<tr> ..etc Thanks for any Help.

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• How to implement Xml Serialization with inherited classes in C#

  - by liorafar

  I have two classes : base class name Component and inheritd class named DBComponent [Serializable] public class Component { private string name = string.Empty; private string description = string.Empty; } [Serializable] public class DBComponent : Component { private List<string> spFiles = new List<string>(); // Storage Procedure Files [XmlArrayItem("SPFile", typeof(string))] [XmlArray("SPFiles")] public List<string> SPFiles { get { return spFiles; } set { spFiles = value; } } public DBComponent(string name, string description) : base(name, description) { } } [Serializable] public class ComponentsCollection { private static ComponentsCollection instance = null; private List<Component> components = new List<Component>(); public List<Component> Components { get { return components; } set { components = value; } } public static ComponentsCollection GetInstance() { if (ccuInstance == null) { lock (lockObject) { if (instance == null) PopulateComponents(); } } return instance; } private static void PopulateComponents() { instance = new CCUniverse(); XmlSerializer xs = new XmlSerializer(instance.GetType()); instance = xs.Deserialize(XmlReader.Create("Components.xml")) as ComponentsCollection; } } } I want read\write from a Xml file. I know that I need to implement the Serialization for DBComponent class otherwise it will not read it.But i cannot find any simple article for that. all the articles that I found were too complex for this simple scenario. The Xml file looks like this: <?xml version="1.0" encoding="utf-8" ?> <ComponentsCollection> <Components> <DBComponent Name="Tenant Historical Database" Description="Tenant Historical Database"> <SPFiles> <SPFile>Setup\TenantHistoricalSP.sql</SPFile> </SPFiles> </DBComponent> <Component Name="Agent" Description="Desktop Agent" /> </Components> </ComponentsCollection> Can someone please give me a simple example of how to read this kind of xml file and what should be implemented ? Thanks Lior

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• Consolidating coding styles: Funcs, private method, single method classes

  - by jdoig

  Hi all, We currently have 3 devs with, some, conflicting styles and I'm looking for a way to bring peace to the kingdom... The Coders: Foo 1: Likes to use Func's & Action's inside public methods. He uses actions to alias off lengthy method calls and Func's to perform simple tasks that can be expressed in 1 or 2 lines and will be used frequently through out the code Pros: The main body of his code is succinct and very readable, often with only one or 2 public methods per class and rarely any private methods. Cons: The start of methods contain blocks of lambda rich code that other developers don't enjoy reading; and, on occasion, can contain higher order functions that other dev's REALLY don't like reading. Foo 2: Likes to create a private method for (almost) everything the public method will have to do . Pros: Public methods remain small and readable (to all developers). Cons: Private methods are numerous. With private methods that call into other private methods, that call into... etc, etc. Making code hard to navigate. Foo 3: Likes to create a public class with a, single, public method for every, non-trivial, task that needs performing, then dependency inject them into other objects. Pros: Easily testable, easy to understand (one object, one responsibility). Cons: project gets littered by classes, opening multiple class files to understand what code does makes navigation awkward. It would be great to take the best of all these techniques... Foo-1 Has really nice, readable (almost dsl-like) code... for the most part, except for all the Action and Func lambda shenanigans bulked together at the start of a method. Foo-3 Has highly testable and extensible code that just feels a bit "belt-&-braces" for some solutions and has some code-navigation niggles (constantly hitting F12 in VS and opening 5 other .cs files to find out what a single method does). And Foo-2... Well I'm not sure I like anything about the one-huge .cs file with 2 public methods and 12 private ones, except for the fact it's easier for juniors to dig into. I admit I grossly over-simplified the explanations of those coding styles; but if any one knows of any patterns, practices or diplomatic-manoeuvres that can help unite our three developers (without just telling any of them to just "stop it!") that would be great. From a feasibility standpoint : Foo-1's style meets with the most resistance due to some developers finding lambda and/or Func's hard to read. Foo-2's style meets with a less resistance as it's just so easy to fall into. Foo-3's style requires the most forward thinking and is difficult to enforce when time is short. Any ideas on some coding styles or conventions that can make this work?

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• Parameters not being passed into template when using the .Net transform classes

  - by Chris F

  I am using the .Net XslCompiledTranform to run some simple XSLT (see below for a simplified example). The example XSLT is meant to do simply show the value of the parameter that is passed in to the template. The output is what I expect it to be (i.e. <result xmlns:p1="http://www.doesnotexist.com"> <valueOfParamA>valueA</valueOfParamA> </result> when I use Saxon 9.0, but when I use XslCompiledTransform (XslTransform) in .net I get <result xmlns:p1="http://www.doesnotexist.com"> <valueOfParamA></valueOfParamA> </result> The problem is that that the parameter value of paramA is not being passed into the template when I use the .Net classes. I completely stumped as to why. when I step through in Visual Studio, the debugger says that the template will be called with paramA='valueA' but when execution switches to the template the value of paramA is blank. Can anyone explain why this is happening? Is this a bug in the MS implementation or (more likely) am I doing something that is forbidden in XSLT? Any help greatly appreciated. This is the XSLT that I am using <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:extfn="http://exslt.org/common" exclude-result-prefixes="extfn" xmlns:p1="http://www.doesnotexist.com"> <!-- Replace msxml with xmlns:extfn="http://exslt.org/common" xmlns:extfn="urn:schemas-microsoft-com:xslt" --> <xsl:output method="xml" indent="yes"/> <xsl:template match="/"> <xsl:variable name="resultTreeFragment"> <p1:foo> </p1:foo> </xsl:variable> <xsl:variable name="nodeset" select="extfn:node-set($resultTreeFragment)"/> <result> <xsl:apply-templates select="$nodeset" mode="AParticularMode"> <xsl:with-param name="paramA" select="'valueA'"/> </xsl:apply-templates> </result> </xsl:template> <xsl:template match="@* | node()" mode="AParticularMode"> <xsl:param name="paramA"/> <valueOfParamA> <xsl:value-of select="$paramA"/> </valueOfParamA> </xsl:template> </xsl:stylesheet>

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• Can I use a static cache Helper method in a NET MVC controller?

  - by Euston

  I realise there have been a few posts regarding where to add a cache check/update and the separation of concerns between the controller, the model and the caching code. There are two great examples that I have tried to work with but being new to MVC I wonder which one is the cleanest and suits the MVC methodology the best? I know you need to take into account DI and unit testing. Example 1 (Helper method with delegate) ...in controller var myObject = CacheDataHelper.Get(thisID, () => WebServiceServiceWrapper.GetMyObjectBythisID(thisID)); Example 2 (check for cache in model class) in controller var myObject = WebServiceServiceWrapper.GetMyObjectBythisID(thisID)); then in model class.............. if (!CacheDataHelper.Get(cachekey, out myObject)) { //do some repository processing // Add obect to cache CacheDataHelper.Add(myObject, cachekey); } Both use a static cache helper class but the first example uses a method signature with a delegate method passed in that has the name of the repository method being called. If the data is not in cache the method is called and the cache helper class handles the adding or updating to the current cache. In the second example the cache check is part of the repository method with an extra line to call the cache helper add method to update the current cache. Due to my lack of experience and knowledge I am not sure which one is best suited to MVC. I like the idea of calling the cache helper with the delegate method name in order to remove any cache code in the repository but I am not sure if using the static method in the controller is ideal? The second example deals with the above but now there is no separation between the caching check and the repository lookup. Perhaps that is not a problem as you know it requires caching anyway?

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• Is it okay to pass injected EntityManagers to EJB bean's helper classes and use it?

  - by Zwei steinen

  We have some JavaEE5 stateless EJB bean that passes the injected EntityManager to its helpers. Is this safe? It has worked well until now, but I found out some Oracle document that states its implementation of EntityManager is thread-safe. Now I wonder whether the reason we did not have issues until now, was only because the implementation we were using happened to be thread-safe (we use Oracle). @Stateless class SomeBean { @PersistenceContext private EntityManager em; private SomeHelper helper; @PostConstruct public void init(){ helper = new SomeHelper(em); } @Override public void business(){ helper.doSomethingWithEm(); } } Actually it makes sense.. If EntityManager is thread-unsafe, a container would have to do inercept business() this.em = newEntityManager(); business(); which will not propagate to its helper classes. If so, what is the best practice in this kind of a situation? Passing EntityManagerFactory instead of EntityManager?

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• Java - is this an idiom or pattern, behavior classes with no state

  - by Berlin Brown

  I am trying to incorporate more functional programming idioms into my java development. One pattern that I like the most and avoids side effects is building classes that have behavior but they don't necessarily have any state. The behavior is locked into the methods but they only act on the parameters passed in. The code below is code I am trying to avoid: public class BadObject { private Map<String, String> data = new HashMap<String, String>(); public BadObject() { data.put("data", "data"); } /** * Act on the data class. But this is bad because we can't * rely on the integrity of the object's state. */ public void execute() { data.get("data").toString(); } } The code below is nothing special but I am acting on the parameters and state is contained within that class. We still may run into issues with this class but that is an issue with the method and the state of the data, we can address issues in the routine as opposed to not trusting the entire object. Is this some form of idiom? Is this similar to any pattern that you use? public class SemiStatefulOOP { /** * Private class implies that I can access the members of the <code>Data</code> class * within the <code>SemiStatefulOOP</code> class and I can also access * the getData method from some other class. * * @see Test1 * */ class Data { protected int counter = 0; public int getData() { return counter; } public String toString() { return Integer.toString(counter); } } /** * Act on the data class. */ public void execute(final Data data) { data.counter++; } /** * Act on the data class. */ public void updateStateWithCallToService(final Data data) { data.counter++; } /** * Similar to CLOS (Common Lisp Object System) make instance. */ public Data makeInstance() { return new Data(); } } // End of Class // Issues with the code above: I wanted to declare the Data class private, but then I can't really reference it outside of the class: I can't override the SemiStateful class and access the private members. Usage: final SemiStatefulOOP someObject = new SemiStatefulOOP(); final SemiStatefulOOP.Data data = someObject.makeInstance(); someObject.execute(data); someObject.updateStateWithCallToService(data);

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• Javascript click function for multiple Classes

  - by Jason Bassett

  So basically I have this little social networking site which allow comments. I've built a comment section that will slide down once a user clicks "Comment" and it slides down under the users status. My problem is that right now, the JavaScript only works on ONE post ID, and not the rest obviously seeing you can only use an ID once. But of course if I use classes instead, All the comment sections slide down because now they're all the same class. See below for my HTML and JavaScript. So if someone has a better method out there, please help :) $(function () { $(".comment-box").slideUp(); //when "comment" is clicked, slide down the comment box. if ($(".comment-box-btn").click(function () { $(".comment-box").slideDown(); })); //when "cancel" is clicked, slide up the comment box. if ($(".close-comment-box").click(function () { $(".comment-box").slideUp() })); }); And here's the HTML used //anchor for "Comment" <a class="comment-box-btn" href="#"><i class="icon-comment"></i> Comment</a> //comment box <div class="row comment-box" style="display:none;"> <div class="col-md-12"> <form accept-charset="UTF-8" action="" method="post"> <textarea class="form-control animated" cols="180" id="new-comment" name="comment" placeholder="Comment.." rows="1"></textarea> <div class="text-right" style="margin-top:20px;"> <a class="btn btn-default close-comment-box" href="#"> <span class="glyphicon glyphicon-remove"></span> Cancel</a> <button class="btn btn-info" type="submit">Comment</button> </div> </form> </div> </div>

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• Exporting to XML, including embedded classes

  - by Andy

  I have an object config which has some properties. I can export this ok, however, it also has an ArrayList which relates to embedded classes which I can't get to appear when I export to XML. Any pointers would be helpful. Export Method public String exportXML(config conf, String path) { String success = ""; try { FileOutputStream fstream = new FileOutputStream(path); try { XMLEncoder ostream = new XMLEncoder(fstream); try { ostream.writeObject(conf); ostream.flush(); } finally { ostream.close(); } } finally { fstream.close(); } } catch (Exception ex) { success = ex.getLocalizedMessage(); } return success; } Config Class (some detail stripped to keep size down) public class config { protected String author = ""; protected String website = ""; private ArrayList questions = new ArrayList(); public config(){ } public void addQuestion(String name) { questions.add(new question(questions.size(), name)); } public void removeQuestion(int id) { questions.remove(id); for (int c = 0; c <= questions.size(); c++) { question q = (question) (questions.get(id)); q.setId(c); } questions.trimToSize(); } public config.question getQuestion(int id){ return (question)questions.get(id); } /** * There can be multiple questions per config. * Questions store all the information regarding what questions are * asked of the user, including images, descriptions, and answers. */ public class question { protected int id; protected String title; protected ArrayList answers; public question(int id, String title) { this.id = id; this.title = title; } public int getId() { return id; } public void setId(int id) { this.id = id; } public void addAnswer(String name) { answers.add(new answer(answers.size(), name)); } public void removeAnswer(int id) { answers.remove(id); for (int c = 0; c <= answers.size(); c++) { answer a = (answer) (answers.get(id)); a.setId(c); } answers.trimToSize(); } public config.question.answer getAnswer(int id){ return (answer)answers.get(id); } public class answer { protected int id; protected String title; public answer(int id, String title) { this.id = id; this.title = title; } public int getId() { return id; } public void setId(int id) { this.id = id; } } } } Resultant XML File <?xml version="1.0" encoding="UTF-8"?> <java version="1.6.0_18" class="java.beans.XMLDecoder"> <object class="libConfig.config"> <void property="appName"> <string>xxx</string> </void> <void property="author"> <string>Andy</string> </void> <void property="website"> <string>www.example.com/dsx.xml</string> </void> </object> </java>

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• How to use objects as modules/functors in Scala?

  - by Jeff

  Hi. I want to use object instances as modules/functors, more or less as shown below: abstract class Lattice[E] extends Set[E] { val minimum: E val maximum: E def meet(x: E, y: E): E def join(x: E, y: E): E def neg(x: E): E } class Calculus[E](val lat: Lattice[E]) { abstract class Expr case class Var(name: String) extends Expr {...} case class Val(value: E) extends Expr {...} case class Neg(e1: Expr) extends Expr {...} case class Cnj(e1: Expr, e2: Expr) extends Expr {...} case class Dsj(e1: Expr, e2: Expr) extends Expr {...} } So that I can create a different calculus instance for each lattice (the operations I will perform need the information of which are the maximum and minimum values of the lattice). I want to be able to mix expressions of the same calculus but not be allowed to mix expressions of different ones. So far, so good. I can create my calculus instances, but problem is that I can not write functions in other classes that manipulate them. For example, I am trying to create a parser to read expressions from a file and return them; I also was trying to write an random expression generator to use in my tests with ScalaCheck. Turns out that every time a function generates an Expr object I can't use it outside the function. Even if I create the Calculus instance and pass it as an argument to the function that will in turn generate the Expr objects, the return of the function is not recognized as being of the same type of the objects created outside the function. Maybe my english is not clear enough, let me try a toy example of what I would like to do (not the real ScalaCheck generator, but close enough). def genRndExpr[E](c: Calculus[E], level: Int): Calculus[E]#Expr = { if (level > MAX_LEVEL) { val select = util.Random.nextInt(2) select match { case 0 => genRndVar(c) case 1 => genRndVal(c) } } else { val select = util.Random.nextInt(3) select match { case 0 => new c.Neg(genRndExpr(c, level+1)) case 1 => new c.Dsj(genRndExpr(c, level+1), genRndExpr(c, level+1)) case 2 => new c.Cnj(genRndExpr(c, level+1), genRndExpr(c, level+1)) } } } Now, if I try to compile the above code I get lots of error: type mismatch; found : plg.mvfml.Calculus[E]#Expr required: c.Expr case 0 = new c.Neg(genRndExpr(c, level+1)) And the same happens if I try to do something like: val boolCalc = new Calculus(Bool) val e1: boolCalc.Expr = genRndExpr(boolCalc) Please note that the generator itself is not of concern, but I will need to do similar things (i.e. create and manipulate calculus instance expressions) a lot on the rest of the system. Am I doing something wrong? Is it possible to do what I want to do? Help on this matter is highly needed and appreciated. Thanks a lot in advance. After receiving an answer from Apocalisp and trying it. Thanks a lot for the answer, but there are still some issues. The proposed solution was to change the signature of the function to: def genRndExpr[E, C <: Calculus[E]](c: C, level: Int): C#Expr I changed the signature for all the functions involved: getRndExpr, getRndVal and getRndVar. And I got the same error message everywhere I call these functions and got the following error message: error: inferred type arguments [Nothing,C] do not conform to method genRndVar's type parameter bounds [E,C genRndVar(c) Since the compiler seemed to be unable to figure out the right types I changed all function call to be like below: case 0 => new c.Neg(genRndExpr[E,C](c, level+1)) After this, on the first 2 function calls (genRndVal and genRndVar) there were no compiling error, but on the following 3 calls (recursive calls to genRndExpr), where the return of the function is used to build a new Expr object I got the following error: error: type mismatch; found : C#Expr required: c.Expr case 0 = new c.Neg(genRndExpr[E,C](c, level+1)) So, again, I'm stuck. Any help will be appreciated.

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• JAXB: Unmarshalling does not always populate certain classes?

  - by user278458

  Hello, I have a JAXB class generation problem I was hoping to get some help with. Here's the part of the XML that is the source of my problem... Code: <xs:complexType name="IDType"> <xs:choice minOccurs="0" maxOccurs="2"> <xs:element name="DriversLicense" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="SSN" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="CompanyID" minOccurs="0" maxOccurs="1" type="an..35" /> </xs:choice> </xs:complexType> <xs:simpleType name="an..35"> <xs:restriction base="an"> <xs:maxLength value="35" /> </xs:restriction> </xs:simpleType> <xs:simpleType name="an"> <xs:restriction base="xs:string"> <xs:pattern value="[ !-~]*" /> </xs:restriction> </xs:simpleType> ...now this will generate JAXBElement types due the the "choice" with a "maxOccurs 1" . I want to avoid those, so I did that by modifying the code to use a "Wrapper" element and move the maxOccurs up to a sequence tag as follows... Code: <xs:complexType name="IDType"> <xs:sequence maxOccurs="2"> <xs:element name=Wrapper> <xs:complexType> <xs:choice> <xs:element name="DriversLicense" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="SSN" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="CompanyID" minOccurs="0" maxOccurs="1" type="an..35" /> </xs:choice> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> <xs:simpleType name="an..35"> <xs:restriction base="an"> <xs:maxLength value="35" /> </xs:restriction> </xs:simpleType> <xs:simpleType name="an"> <xs:restriction base="xs:string"> <xs:pattern value="[ !-~]*" /> </xs:restriction> </xs:simpleType> For class generating, looks like it works great - the JAXB element is replaced with a list of wrappers as String (i.e. List ) and compiles fine. However, when I unmarshall the actual XML data into the generated classes the data in the wrapper class is not populated - yet JAXB does not throw an exception. My question is: Do I need to change the schema a different way to make this work? Or is there something I can add/change/delete to the generated code or annotations? Appreciate any help you can offer! Thanks.

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• Series of abstract classes and NHibernate

  - by Chris Cowdery-Corvan

  Hello, and first off thanks for your time to look at this. For a research project I'm working on, I have a somewhat complex design (which I've been given) to persist to a database via NHibernate. Here's an example of the class hierarchy: TransitStrategy, TransportationCompany and TransportationLocation are all abstract classes. The XML configuration I have is presently: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Vacationizer" namespace="Vacationizer.Domain.Transit"> <class name="TransitStrategy"> <id name="TransitStrategyId"> <generator class="guid" /> </id> <property name="Restrictions" /> <joined-subclass name="Flight" table="Flight_TransitStrategy"> <key column="TransitStrategyId" /> <property name="DepartingAirport" /> <property name="ArrivingAirport" /> <property name="Airline" /> <property name="FlightNumber" /> <property name="FlightArrivalTime" /> <property name="FlightDepartureTime" /> </joined-subclass> <joined-subclass name="RentalCar" table="RentalCar_TransitStrategy"> <key column="TransitStrategyId" /> <property name="RentalCarBranch" /> <property name="CarMake" /> <property name="CarModel" /> <property name="CarYear" /> <property name="CarColor" /> <property name="RentalBegins" /> <property name="RentalEnds" /> </joined-subclass> </class> <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Vacationizer" namespace="Vacationizer.Domain.Transit"> <class name="TransportationCompany"> <id name="TransportationCompanyId"> <generator class="guid" /> </id> <property name="Name" /> <property name="Reviews" /> <property name="Website" /> <property name="Photo" /> <joined-subclass name="Airline" table="Airline_TransportationCompany"> <key column="TransportationLocationId" /> </joined-subclass> <joined-subclass name="RentalCarAgency" table="RentalCarAgency_TransportationCompany"> <key column="TransportationLocationId" /> </joined-subclass> </class> <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Vacationizer" namespace="Vacationizer.Domain.Transit"> <class name="TransportationLocation"> <id name="TransportationLocationId"> <generator class="guid" /> </id> <property name="Name" /> <property name="Image" /> <property name="Geolocation" /> <property name="Reviews" /> <!-- <property name="HoursOpen" />--> <property name="PhoneNumber" /> <property name="FaxNumber" /> <joined-subclass name="Airport" table="Airport_TransportationLocation"> <key column="TransportationLocationId" /> <property name="AirportCode" /> <property name="Website" /> </joined-subclass> <joined-subclass name="RentalCarBranch" table="RentalCarBranch_TransportationLocation"> <key column="TransitStrategyId" /> <property name="Agency" /> </joined-subclass> </class> However, whenever I try to use this schema I get this error/stack trace: ------ Test started: Assembly: Vacationizer.Tests.dll ------ TestCase 'M:Vacationizer.Tests.VacationRepository_Fixture.TestFixtureSetUp' failed: Could not compile the mapping document: Vacationizer.Mappings.TransitStrategy.hbm.xml NHibernate.MappingException: Could not compile the mapping document: Vacationizer.Mappings.TransitStrategy.hbm.xml ---> NHibernate.MappingException: Problem trying to set property type by reflection ---> NHibernate.MappingException: class Vacationizer.Domain.Transit.RentalCar, Vacationizer, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null not found while looking for property: RentalCarBranch ---> NHibernate.PropertyNotFoundException: Could not find a getter for property 'RentalCarBranch' in class 'Vacationizer.Domain.Transit.RentalCar' at NHibernate.Properties.BasicPropertyAccessor.GetGetter(Type type, String propertyName) at NHibernate.Util.ReflectHelper.ReflectedPropertyClass(String className, String name, String accessorName) --- End of inner exception stack trace --- at NHibernate.Util.ReflectHelper.ReflectedPropertyClass(String className, String name, String accessorName) at NHibernate.Mapping.SimpleValue.SetTypeUsingReflection(String className, String propertyName, String accesorName) --- End of inner exception stack trace --- at NHibernate.Mapping.SimpleValue.SetTypeUsingReflection(String className, String propertyName, String accesorName) at NHibernate.Cfg.XmlHbmBinding.ClassBinder.CreateProperty(IValue value, String propertyName, String className, XmlNode subnode, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.ClassBinder.PropertiesFromXML(XmlNode node, PersistentClass model, IDictionary`2 inheritedMetas, UniqueKey uniqueKey, Boolean mutable, Boolean nullable, Boolean naturalId) at NHibernate.Cfg.XmlHbmBinding.JoinedSubclassBinder.HandleJoinedSubclass(PersistentClass model, XmlNode subnode, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.ClassBinder.PropertiesFromXML(XmlNode node, PersistentClass model, IDictionary`2 inheritedMetas, UniqueKey uniqueKey, Boolean mutable, Boolean nullable, Boolean naturalId) at NHibernate.Cfg.XmlHbmBinding.RootClassBinder.Bind(XmlNode node, HbmClass classSchema, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.MappingRootBinder.AddRootClasses(XmlNode parentNode, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.MappingRootBinder.Bind(XmlNode node) at NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) --- End of inner exception stack trace --- at NHibernate.Cfg.Configuration.LogAndThrow(Exception exception) at NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) at NHibernate.Cfg.Configuration.ProcessMappingsQueue() at NHibernate.Cfg.Configuration.AddDocumentThroughQueue(NamedXmlDocument document) at NHibernate.Cfg.Configuration.AddXmlReader(XmlReader hbmReader, String name) at NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream, String name) at NHibernate.Cfg.Configuration.AddResource(String path, Assembly assembly) at NHibernate.Cfg.Configuration.AddAssembly(Assembly assembly) at NHibernate.Cfg.Configuration.AddAssembly(String assemblyName) at NHibernate.Cfg.Configuration.DoConfigure(IHibernateConfiguration hc) at NHibernate.Cfg.Configuration.Configure() VacationRepository_Fixture.cs(24,0): at Vacationizer.Tests.VacationRepository_Fixture.TestFixtureSetUp() 0 passed, 1 failed, 0 skipped, took 8.38 seconds (Ad hoc). Any ideas on how I can implement this differently? Thanks very much!

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• How do I change variables from different classes?

  - by Dan T

  Before I delve into it, I'm very new to Android and I have just started learning Java last month. I've hit bumps while trying to develop my first simple app. Most of these hurdles were jumped thanks to random tutorials online. MY CODE IS VERY MESSY. Any tips are appreciated. The question above is quite broad, but this is what I want to do: It's a essentially a blood alcohol content calculator / drink keeper-tracker. Basic layout: http://i.imgur.com/JGuh7.jpg The buttons along the bottom are just regular buttons, not ImageButtons (had problems with that) Here's some example code of one: <Button android:id="@+id/Button01" android:layout_width="wrap_content" android:layout_marginRight="5dp" android:background="@drawable/addbeer"/> The buttons and TextView are all in main.xml. I have variables defined in a class called Global.java: package com.dantoth.drinkingbuddy; import android.app.Activity; public class Global extends Activity{ public static double StandardDrinks = 0; public static double BeerOunces = 12; public static double BeerPercentAlcohol = .05; public static double BeerDrink = BeerOunces * BeerPercentAlcohol; public static double BeerDrinkFinal = BeerDrink * 1.6666666; public static double ShotOunces = 1.5; public static double ShotPercentAlcohol = .4; public static double ShotDrink = ShotOunces * ShotPercentAlcohol; public static double ShotDrinkFinal = ShotDrink * 1.6666666; public static double WineOunces = 5; public static double WinePercentAlcohol = .12; public static double WineDrink = WineOunces * WinePercentAlcohol; public static double WineDrinkFinal = WineDrink * 1.6666666; public static double OtherOunces; public static double OtherPercentAlcohol; public static double OtherDrink = OtherOunces * (OtherPercentAlcohol * .01); public static double OtherDrinkFinal = OtherDrink * 1.6666666; public static double GenderConstant = 7.5; //9 for female public static double Weight = 180; public static double TimeDrinking = 60; public static double Hours = TimeDrinking / 60; public static double Bac = ((StandardDrinks / 2) * (GenderConstant / Weight)) - (0.017 * Hours); } The last variable is the important part. It calculates your BAC based on the factors involved. When I press the add beer button (Button01) I make it add 1 to StandardDrinks, simulating drinking one beer. The other variables in the Bac formula have values assigned to them in Global.java. The code that makes the beer button do stuff is in my regular class, drinkingbuddy.java: public class DrinkingBuddy extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button button = (Button) findViewById(R.id.Button01); button.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Global.StandardDrinks = Global.StandardDrinks + Global.BeerDrinkFinal; Toast.makeText(DrinkingBuddy.this, "Mmmm... Beer", Toast.LENGTH_SHORT).show(); } }); By my perception, StandardDrinks should now have a value of 1. However, when I click the Calculate BAC button (Button05) it merely outputs the variable Bac as if StandardDrinks was still set to 0. Here is the code for the Calculate BAC button (Button05): Button button4 = (Button) findViewById(R.id.Button05); button4.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { TextView texty; texty = (TextView) findViewById(R.id.texty1); texty.setText("Your BAC is " + Global.Bac ); } }); It outputs the following to the text view: "Your BAC is -0.017". This is the Bac value for if StandardDrinks was still 0, so obviously there is some problem communicating between the classes. Can anyone help me?? The other elements of the formula (weight, time spent drinking, and the alcohol %'s and such) are variables because I will ultimately allow the user to change those values in the settings. I've heard around the water cooler that global variables are not good programming style, but this is the closest I've come to getting it to work. Any other ways of doing it are very much welcomed!

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• how to serialize / deserialize classes defined in .proto (protobuf)

  - by make

  Hi, Could someone please help me with serialization/deserialization classes defined in .proto (protobuf). here is an exp that I am trying to build: file.proto message Data{ required string x1 = 1; required uint32 x2 = 2; required float x3 = 3; } message DataExge { repeated Data data = 1; } client.cpp ... void serialize(const DataExge &data_snd){ try { ofstream ofs("DataExge"); data_snd.SerializeToOstream(&ofs); } catch(exception &e) { cerr << "serialize/exception: " << e.what() << endl; exit(1); } } void deserialize(DataExge &data_rec){ try { ifstream ifs("DataExge"); data_rec.ParseFromIstream(&ifs); } catch(exception& e) { cerr << "deserialize/exception: " << e.what() << endl; exit(1); } } int main(){ ... DataExge dataexge; Data *dat = dataexge.add_data(); char *y1 = "operation1"; uint32_t y2 = 123 ; float y3 = 3.14; // assigning data to send() dat->set_set_x1(y1); dat->set_set_x2(y2); dat->set_set_x3(y3); //sending data to the client serialize(dataexge); if (send(socket, &dataexge, sizeof(dataexge), 0) < 0) { cerr << "send() failed" ; exit(1); } //receiving data from the server deserialize(dataexge); if (recv(socket, &dataexge, sizeof(dataexge), 0) < 0) { cerr << "recv() failed"; exit(1); } //printing received data cout << dat->x1() << "\n"; cout << dat->x2() << "\n"; cout << dat->x3() << "\n"; ... } server.cpp ... void serialize(const DataExge &data_snd){ try { ofstream ofs("DataExge"); data_snd.SerializeToOstream(&ofs); } catch(exception &e) { cerr << "serialize/exception: " << e.what() << endl; exit(1); } } void deserialize(DataExge &data_rec){ try { ifstream ifs("DataExge"); data_rec.ParseFromIstream(&ifs); } catch(exception& e) { cerr << "deserialize/exception: " << e.what() << endl; exit(1); } } int main(){ ... DataExge dataexge; Data *dat = dataexge.add_data(); //receiving data from the client deserialize(dataexge); if (recv(socket, &dataexge, sizeof(dataexge), 0) < 0) { cerr << "recv() failed"; exit(1); } //printing received data cout << dat->x1() << "\n"; cout << dat->x2() << "\n"; cout << dat->x3() << "\n"; // assigning data to send() dat->set_set_x1("operation2"); dat->set_set_x2(dat->x2() + 1); dat->set_set_x3(dat->x3() + 1.1); //sending data to the client serialize(dataexge); //error// I am getting error at this line ... if (send(socket, &dataexge, sizeof(dataexge), 0) < 0) { cerr << "send() failed" ; exit(1); } ... } Thanks for your help and replies -

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• Design advice for avoiding change in several classes

  - by Anders Svensson

  Hi, I'm trying to figure out how to design a small application more elegantly, and make it more resistant to change. Basically it is a sort of project price calculator, and the problem is that there are many parameters that can affect the pricing. I'm trying to avoid cluttering the code with a lot of if-clauses for each parameter, but still I have e.g. if-clauses in two places checking for the value of the size parameter. I have the Head First Design Patterns book, and have tried to find ideas there, but the closest I got was the decorator pattern, which has an example where starbuzz coffee sets prices depending first on condiments added, and then later in an exercise by adding a size parameter (Tall, Grande, Venti). But that didn't seem to help, because adding that parameter still seemed to add if-clause complexity in a lot of places (and this being an exercise they didn't explain that further). What I am trying to avoid is having to change several classes if a parameter were to change or a new parameter added, or at least change in as few places as possible (there's some fancy design principle word for this that I don't rememeber :-)). Here below is the code. Basically it calculates the price for a project that has the tasks "Writing" and "Analysis" with a size parameter and different pricing models. There will be other parameters coming in later too, like "How new is the product?" (New, 1-5 years old, 6-10 years old), etc. Any advice on the best design would be greatly appreciated, whether a "design pattern" or just good object oriented principles that would make it resistant to change (e.g. adding another size, or changing one of the size values, and only have to change in one place rather than in several if-clauses): public class Project { private readonly int _numberOfProducts; protected Size _size; public Task Analysis { get; set; } public Task Writing { get; set; } public Project(int numberOfProducts) { _numberOfProducts = numberOfProducts; _size = GetSize(); Analysis = new AnalysisTask(numberOfProducts, _size); Writing = new WritingTask(numberOfProducts, _size); } private Size GetSize() { if (_numberOfProducts <= 2) return Size.small; if (_numberOfProducts <= 8) return Size.medium; return Size.large; } public double GetPrice() { return Analysis.GetPrice() + Writing.GetPrice(); } } public abstract class Task { protected readonly int _numberOfProducts; protected Size _size; protected double _pricePerHour; protected Dictionary<Size, int> _hours; public abstract int TotalHours { get; } public double Price { get; set; } protected Task(int numberOfProducts, Size size) { _numberOfProducts = numberOfProducts; _size = size; } public double GetPrice() { return _pricePerHour * TotalHours; } } public class AnalysisTask : Task { public AnalysisTask(int numberOfProducts, Size size) : base(numberOfProducts, size) { _pricePerHour = 850; _hours = new Dictionary<Size, int>() { { Size.small, 56 }, { Size.medium, 104 }, { Size.large, 200 } }; } public override int TotalHours { get { return _hours[_size]; } } } public class WritingTask : Task { public WritingTask(int numberOfProducts, Size size) : base(numberOfProducts, size) { _pricePerHour = 650; _hours = new Dictionary<Size, int>() { { Size.small, 125 }, { Size.medium, 100 }, { Size.large, 60 } }; } public override int TotalHours { get { if (_size == Size.small) return _hours[_size] * _numberOfProducts; if (_size == Size.medium) return (_hours[Size.small] * 2) + (_hours[Size.medium] * (_numberOfProducts - 2)); return (_hours[Size.small] * 2) + (_hours[Size.medium] * (8 - 2)) + (_hours[Size.large] * (_numberOfProducts - 8)); } } } public enum Size { small, medium, large } public partial class Form1 : Form { public Form1() { InitializeComponent(); List<int> quantities = new List<int>(); for (int i = 0; i < 100; i++) { quantities.Add(i); } comboBoxNumberOfProducts.DataSource = quantities; } private void comboBoxNumberOfProducts_SelectedIndexChanged(object sender, EventArgs e) { Project project = new Project((int)comboBoxNumberOfProducts.SelectedItem); labelPrice.Text = project.GetPrice().ToString(); labelWriterHours.Text = project.Writing.TotalHours.ToString(); labelAnalysisHours.Text = project.Analysis.TotalHours.ToString(); } } At the end is a simple current calling code in the change event for a combobox that set size... (BTW, I don't like the fact that I have to use several dots to get to the TotalHours at the end here either, as far as I can recall, that violates the "principle of least knowledge" or "the law of demeter", so input on that would be appreciated too, but it's not the main point of the question) Regards, Anders

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• Problem in generation of custom classes at web service client

  - by user443324

  I have a web service which receives an custom object and returns another custom object. It can be deployed successfully on GlassFish or JBoss. @WebMethod(operationName = "providerRQ") @WebResult(name = "BookingInfoResponse" , targetNamespace = "http://tlonewayresprovidrs.jaxbutil.rakes.nhst.com/") public com.nhst.rakes.jaxbutil.tlonewayresprovidrs.BookingInfoResponse providerRQ(@WebParam(name = "BookingInfoRequest" , targetNamespace = "http://tlonewayresprovidrq.jaxbutil.rakes.nhst.com/") com.nhst.rakes.jaxbutil.tlonewayresprovidrq.BookingInfoRequest BookingInfoRequest) { com.nhst.rakes.jaxbutil.tlonewayresprovidrs.BookingInfoResponse BookingInfoResponse = new com.nhst.rakes.jaxbutil.tlonewayresprovidrs.BookingInfoResponse(); return BookingInfoResponse; } But when I create a client for this web service, two instances of BookingInfoRequest and BookingInfoResponse generated even I need only one instance. This time an error is returned that says multiple classes with same name are can not be possible....... Here is wsdl..... <?xml version='1.0' encoding='UTF-8'?><!-- Published by JAX-WS RI at http://jax-ws.dev.java.net. RI's version is JAX-WS RI 2.2.1-hudson-28-. --><!-- Generated by JAX-WS RI at http://jax-ws.dev.java.net. RI's version is JAX-WS RI 2.2.1-hudson-28-. --><definitions xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:wsp="http://www.w3.org/ns/ws-policy" xmlns:wsp1_2="http://schemas.xmlsoap.org/ws/2004/09/policy" xmlns:wsam="http://www.w3.org/2007/05/addressing/metadata" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:tns="http://demo/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://schemas.xmlsoap.org/wsdl/" targetNamespace="http://demo/" name="DemoJAXBParamService"> <wsp:Policy wsu:Id="DemoJAXBParamPortBindingPolicy"> <ns1:OptimizedMimeSerialization xmlns:ns1="http://schemas.xmlsoap.org/ws/2004/09/policy/optimizedmimeserialization" /> </wsp:Policy> <types> <xsd:schema> <xsd:import namespace="http://tlonewayresprovidrs.jaxbutil.rakes.nhst.com/" schemaLocation="http://localhost:31133/DemoJAXBParamService/DemoJAXBParamService?xsd=1" /> </xsd:schema> <xsd:schema> <xsd:import namespace="http://tlonewayresprovidrs.jaxbutil.rakes.nhst.com" schemaLocation="http://localhost:31133/DemoJAXBParamService/DemoJAXBParamService?xsd=2" /> </xsd:schema> <xsd:schema> <xsd:import namespace="http://tlonewayresprovidrq.jaxbutil.rakes.nhst.com/" schemaLocation="http://localhost:31133/DemoJAXBParamService/DemoJAXBParamService?xsd=3" /> </xsd:schema> <xsd:schema> <xsd:import namespace="http://tlonewayresprovidrq.jaxbutil.rakes.nhst.com" schemaLocation="http://localhost:31133/DemoJAXBParamService/DemoJAXBParamService?xsd=4" /> </xsd:schema> <xsd:schema> <xsd:import namespace="http://demo/" schemaLocation="http://localhost:31133/DemoJAXBParamService/DemoJAXBParamService?xsd=5" /> </xsd:schema> </types> <message name="providerRQ"> <part name="parameters" element="tns:providerRQ" /> </message> <message name="providerRQResponse"> <part name="parameters" element="tns:providerRQResponse" /> </message> <portType name="DemoJAXBParam"> <operation name="providerRQ"> <input wsam:Action="http://demo/DemoJAXBParam/providerRQRequest" message="tns:providerRQ" /> <output wsam:Action="http://demo/DemoJAXBParam/providerRQResponse" message="tns:providerRQResponse" /> </operation> </portType> <binding name="DemoJAXBParamPortBinding" type="tns:DemoJAXBParam"> <wsp:PolicyReference URI="#DemoJAXBParamPortBindingPolicy" /> <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document" /> <operation name="providerRQ"> <soap:operation soapAction="" /> <input> <soap:body use="literal" /> </input> <output> <soap:body use="literal" /> </output> </operation> </binding> <service name="DemoJAXBParamService"> <port name="DemoJAXBParamPort" binding="tns:DemoJAXBParamPortBinding"> <soap:address location="http://localhost:31133/DemoJAXBParamService/DemoJAXBParamService" /> </port> </service> </definitions> So, I want to know that how to generate only one instance(I don't know why two instances are generated at client side?). Please help me to move in right direction.

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