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• JavaScript multithreading

  - by Krzysztof Hasinski

  I'm working on comparison for several different methods of implementing (real or fake) multithreading in JavaScript. As far as I know only webworkers and Google Gears WorkerPool can give you real threads (ie. spread across multiple processors with real parallel execution). I've found the following methods: switch between tasks using yield() use setInterval() (or other non-blocking function) with threads waiting one for another use Google Gears WorkerPool threads (with plugin) use html5 web workers I read related questions and found several variations of the above methods, but most of those questions are old, so there might be a few new ideas. I'm wondering - how else can you achieve multithreading in JavaScript? Any other important methods? UPDATE: As pointed out in comments what I really meant was concurrency. UPDATE 2: I found information that Silverlight + JScript supports multithreading, but I'm unable to verify this. UPDATE 3: Google deprecated Gears: http://code.google.com/apis/gears/api_workerpool.html

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• Is it possible to embed Cockburn style textual UML Use Case content in the code base to improve code

  - by fooledbyprimes

  experimenting with Cockburn use cases in code I was writing some complicated UI code. I decided to employ Cockburn use cases with fish,kite,and sea levels (discussed by Martin Fowler in his book 'UML Distilled'). I wrapped Cockburn use cases in static C# objects so that I could test logical conditions against static constants which represented steps in a UI workflow. The idea was that you could read the code and know what it was doing because the wrapped objects and their public contants gave you ENGLISH use cases via namespaces. Also, I was going to use reflection to pump out error messages that included the described use cases. The idea is that the stack trace could include some UI use case steps IN ENGLISH.... It turned out to be a fun way to achieve a mini,psuedo light-weight Domain Language but without having to write a DSL compiler. So my question is whether or not this is a good way to do this? Has anyone out there ever done something similar? c# example snippets follow Assume we have some aspx page which has 3 user controls (with lots of clickable stuff). User must click on stuff in one particular user control (possibly making some kind of selection) and then the UI must visually cue the user that the selection was successful. Now, while that item is selected, the user must browse through a gridview to find an item within one of the other user controls and then select something. This sounds like an easy thing to manage but the code can get ugly. In my case, the user controls all sent event messages which were captured by the main page. This way, the page acted like a central processor of UI events and could keep track of what happens when the user is clicking around. So, in the main aspx page, we capture the first user control's event. using MyCompany.MyApp.Web.UseCases; protected void MyFirstUserControl_SomeUIWorkflowRequestCommingIn(object sender, EventArgs e) { // some code here to respond and make "state" changes or whatever // // blah blah blah // finally we have this (how did we know to call fish level method?? because we knew when we wrote the code to send the event in the user control) UpdateUserInterfaceOnFishLevelUseCaseGoalSuccess(FishLevel.SomeNamedUIWorkflow.SelectedItemForPurchase) } protected void UpdateUserInterfaceOnFishLevelGoalSuccess(FishLevel.SomeNamedUIWorkflow goal) { switch (goal) { case FishLevel.SomeNamedUIWorkflow.NewMasterItemSelected: //call some UI related methods here including methods for the other user controls if necessary.... break; case FishLevel.SomeNamedUIWorkFlow.DrillDownOnDetails: //call some UI related methods here including methods for the other user controls if necessary.... break; case FishLevel.SomeNamedUIWorkFlow.CancelMultiSelect: //call some UI related methods here including methods for the other user controls if necessary.... break; // more cases... } } } //also we have protected void UpdateUserInterfaceOnSeaLevelGoalSuccess(SeaLevel.SomeNamedUIWorkflow goal) { switch (goal) { case SeaLevel.CheckOutWorkflow.ChangedCreditCard: // do stuff // more cases... } } } So, in the MyCompany.MyApp.Web.UseCases namespace we might have code like this: class SeaLevel... class FishLevel... class KiteLevel... The workflow use cases embedded in the classes could be inner classes or static methods or enumerations or whatever gives you the cleanest namespace. I can't remember what I did originally but you get the picture.

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• Axis2 Webservice -> php

  - by Peter Hagström

  Hi! If I have understood Axis2 correct i can construct a WebService and then access it with any SOAP compatible client. I have a java class with a couple of methods that I have written in Eclipse, and then automatically constructed a service with the Axis2 plugin from WTP. This is the methods of my class. public int test(int i){ return i+2; } public Car CarTest(int speed){ return new Car("Biltest", speed); } public CarFactoryAdapter getCarFactory(){ carFact.getCars().add(new Car("Bmw", 250)); carFact.getCars().add(new Car("seat", 350)); carFact.getCars().add(new Car("saab", 150)); carFact.getCars().add(new Car("volv", 50)); return new CarFactoryAdapter(carFact); } The code seems to work when I try it with soapUI and the Axis2-web interface has recognized the methods of my service. But when Iam trying the methods that receives parameters with PHP´s built in soapClient i get a Unknown exception. The getCarFactory methods works at least as expected, but it seems kind of crippled if I can´t send parameters. Example of non working method invocation. ini_set('soap.wsdl_cache_ttl',0); $client = new SoapClient("http://192.168.128.162:8080/ComplexWebService/services/CarService?wsdl", array('soap_version' => SOAP_1_2, 'trace' => 1)); $ar['i'] = (int)100; print_r($client->__soapCall("test",$ar)); I need to make sure that the SOA framework i choose will be able to comunicate with many platforms, there will be clients in at least PHP and Java, but it would be good if it will work in for example .NET to.

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• State pattern: Why doesn't the context class implement or inherit the State abstract interface/class

  - by Ricket

  I'm reading about the State pattern. I have only just begun, so of course I begin by reading the entire Wikipedia article on it. I noticed that both of the examples in the article have some base abstract class or Java interface for a generic State's methods/functions. Then there are some states which inherit from the base and implement those methods/functions in different ways. Then there's a Context class which has a private member of type State and which, at any time, can be equal to an instance of one of the implementations. That context class also implements the same methods, and passes them onto the current state instance, and then has an additional method to change the state (or depending on design I understand the change of state could be a reaction to one of the implemented methods). Why doesn't this context class specifically "extend" or "implement" the generic State base class/interface?

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• Make is more OOPey - good structure?

  - by Tom

  Hi, I just want advice on whether I could improve structure around a particular class which handles all disk access functions The structure of my program is that I have a class called Disk which gets data from flatfiles and databases on a, you guessed it, hard disk drive. I have functions like LoadTextFileToStringList, WriteStringToTextFile, DeleteLineInTextFile etc which are kind of "generic methods" In the same class I also have some more specific methods such as GetXFromDisk where X might be a particular field in a database table/query. Should I separate out the generic methods from the specialised. Should I make another class which inherits the generic methods. At the moment my class is static as there is no need to have an internal state of the class. I'm not really OOPing am I? Thanks Thomas

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• Why is creating a ring buffer shared by different processes so hard (in C++), what I am doing wrong?

  - by recipriversexclusion

  I am being especially dense about this but it seems I'm missing an important, basic point or something, since what I want to do should be common: I need to create a fixed-size ring buffer object from a manager process (Process M). This object has write() and read() methods to write/read from the buffer. The read/write methods will be called by independent processes (Process R and W) I have implemented the buffer, SharedBuffer<T&>, it allocates buffer slots in SHM using boost::interprocess and works perfectly within a single process. I have read the answers to this question and that one on SO, as well as asked my own, but I'm still in the dark about how to have different processes access methods from a common object. The Boost doc has an example of creating a vector in SHM, which is very similar to what I want, but I want to instantiate my own class. My current options are: Use placement new, as suggested by Charles B. to my question; however, he cautions that it's not a good idea to put non-POD objects in SHM. But my class needs the read/write methods, how can I handle those? Add an allocator to my class definition, e.g. have SharedBuffer<T&, Alloc> and proceed similarly to the vector example given in boost. This sounds really complicated. Change SharedBuffer to a POD class, i.e. get rid of all the methods. But then how to synchronize reading and writing between processes? What am I missing? Fixed-length ring buffers are very common, so either this problem has a solution or else I'm doing something wrong.

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• When to use a module, and when to use a class

  - by Matt Briggs

  I am currently working through the Gregory Brown Ruby Best Practices book. Early on, he is talking about refactoring some functionality from helper methods on a related class, to some methods on module, then had the module extend self. Hadn't seen that before, after a quick google, found out that extend self on a module lets methods defined on the module see each other, which makes sense. Now, my question is when would you do something like this module StyleParser extend self def process(text) ... end def style_tag?(text) ... end end and then refer to it in tests with @parser = Prawn::Document::Text::StyleParser as opposed to just using a class with some class methods on it? is it so that you can use it as a mixin? or are there other reasons I'm not seeing?

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• Interface vs Abstract Class (general OO)

  - by Kave

  Hi, I have had recently two telephone interviews where I've been asked about the differences between an Interface and an Abstract class. I have explained every aspect of them I could think of, but it seems they are waiting for me to mention something specific, and I dont know what it is. From my experience I think the following is true, if i am missing a major point please let me know: Interface: Every single Method declared in an Interface will have to be implemented in the subclass. Only Events, Delegates, Properties (C#) and Methods can exist in a Interface. A class can implement multiple Interfaces. Abstract Class Only Abstract methods have to be implemented by the subclass. An Abstract class can have normal methods with implementations. Abstract class can also have class variables beside Events, Delegates, Properties and Methods. A class can only implement one abstract class only due non-existence of Multi-inheritance in C#. 1) After all that the interviewer came up with the question What if you had an Abstract class with only abstract methods, how would that be different from an interface? I didnt know the answer but I think its the inheritance as mentioned above right? 2) An another interviewer asked me what if you had a Public variable inside the interface, how would that be different than in Abstract Class? I insisted you can't have a public variable inside an interface. I didn't know what he wanted to hear but he wasn't satisfied either. Many Thanks for clarification, Kave See Also: When to use an interface instead of an abstract class and vice versa Interfaces vs. Abstract Classes How do you decide between using an Abstract Class and an Interface?

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• Can a C# method chain be "too long"?

  - by ccornet

  Not in terms of readability, naturally, since you can always arrange the separate methods into separate lines. Rather, is it dangerous, for any reason, to chain an excessively large number of methods together? I use method chaining primarily to save space on declaring individual one-use variables, and traditionally using return methods instead of methods that modify the caller. Except for string methods, those I kinda chain mercilessly. In any case, I worry sometimes about the impact of using exceptionally long method chains all in one line. Let's say I need to update the value of one item based on someone's username. Unfortunately, the shortest method to retrieve the correct user looks something like the following. SPWeb web = GetWorkflowWeb(); SPList list2 = web.Lists["Wars"]; SPListItem item2 = list2.GetItemById(3); SPListItem item3 = item2.GetItemFromLookup("Armies", "Allied Army"); SPUser user2 = item2.GetSPUser("Commander"); SPUser user3 = user2.GetAssociate("Spouse"); string username2 = user3.Name; item1["Contact"] = username2; Everything with a 2 or 3 lasts for only one call, so I might condense it as the following (which also lets me get rid of a would-be-superfluous 1): SPWeb web = GetWorkflowWeb(); item["Contact"] = web.Lists["Armies"] .GetItemById(3) .GetItemFromLookup("Armies", "Allied Army") .GetSPUser("Commander") .GetAssociate("Spouse") .Name; Admittedly, it looks a lot longer when it is all in one line and when you have int.Parse(ddlArmy.SelectedValue.CutBefore(";#", false)) instead of 3. Nevertheless, this is one of the average lengths of these chains, and I can easily foresee some of exceptionally longer counts. Excluding readability, is there anything I should be worried about for these 10+ method chains? Or is there no harm in using really really long method chains?

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• Rails: Overriding ActiveRecord association method

  - by seaneshbaugh

  Is there a way to override one of the methods provided by an ActiveRecord association? Say for example I have the following typical polymorphic has_many :through association: class Story < ActiveRecord::Base has_many :taggings, :as => :taggable has_many :tags, :through => :taggings, :order => :name end class Tag < ActiveRecord::Base has_many :taggings, :dependent => :destroy has_many :stories, :through => :taggings, :source => :taggable, :source_type => "Story" end As you probably know this adds a whole slew of associated methods to the Story model like tags, tags<<, tags=, tags.empty?, etc. How do I go about overriding one of these methods? Specifically the tags<< method. It's pretty easy to override a normal class methods but I can't seem to find any information on how to override association methods. Doing something like def tags<< *new_tags #do stuff end produces a syntax error when it's called so it's obviously not that simple.

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• WCF:recommended naming conventions for same method with different signatures?

  - by mark smith

  Hi there, been creating a few wcf methods and i have a mehtod called IsValidLogin ... there various versions, 1 takes 2 strings, 1 takes an object etc. Of course in WCF you can't overload methods can anyone suggest the best way to name these methods.. I was thinking of IsValidLogin1, IsValidLogin2?? But i am open to any suggestions Thanks in advance

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• When should I open and close a connection to SQL Server

  - by Martin

  I have a simple static class with a few methods in it. Each of those methods open a SqlConnection, query the database and close the connection. This way, I am sure that I always close the connection to the database, but on the other hand, I don't like to always open and close connection. Below is an example of what my methods look like. public static void AddSomething(string something) { using (SqlConnection connection = new SqlConnection("...")) { connection.Open(); // ... connection.Close(); } } Considering that the methods are inside a static class, should I have a static member containing a single SqlConnection? How and when should I drop it? What are the best practices?

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• strategy for observer pattern?

  - by fayer

  I want to use observer pattern for a logging system. We have got logObservers and logObservables. The class that will have to log something will implement iLogObservable and include these methods: private $logObservers = array(); public function addLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function removeLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function write($type, $message) { foreach($this->logObservers as $logObserver) { $logObserver->log($level, $message); ; } } Then I noticed, that a lot of classes that will use logging will have these methods and I have to copy paste. So isn't it better to have these methods in a class I call LogObservable or just Log and then use strategy (instantiate this class inside all classes that will have to log). When I change the methods in Log, all logObservables will be affected. However, I have not seen anyone use observer pattern with strategy pattern yet, but it seems to be very efficient and remove the duplications. What do you think?

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• swing gui improving

  - by radi

  hi all , i am looking for some methods to improve swing gui for example i want to know about new components libraries , new methods to enhance swing performance , new methods to add special effect to swing gui and new plaf for swing . please i want to know how to use this topics and where to find some tutorials about it . thanks.

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• Best way to get an Application Context into a static method in Android

  - by Slapout

  I'm working on an Android application that has several Activities. In it I have a class with several static methods. I would like to be able to call these methods from the different Activities. I'm using the static methods to load data from an xml file via a XmlResourceParser. To create a XmlResourceParser requires a call on the Application Context. So my question is, what is the best way to get a reference to the Application Context into the static methods? Have each Activity get it and pass it in? Store it somehow in a global variable?

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• what is common GIS method?

  - by smile

  hello every one I want to know what is the main methods that used in GIS to connect between the location and their information (spatial access methodes) SAM. I read in some web sites two methods are: vector raster is that methods related what I want??? thank you ^_^

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• C++ converting back and forth from derived and base classes

  - by user127817

  I was wondering if there is a way in C++ to accomplish the following: I have a base class called ResultBase and two class that are Derived from it, Variable and Expression. I have a few methods that do work on vector<ResultBase> . I want to be able to pass in vectors of Variable and Expression into these methods. I can achieve this by creating a vector<ResultBase> and using static_cast to fill it with the members from my vector of Variable/Expression. However, once the vector has run through the methods, I want to be able to get it back as the vector of Result/Expression. I'll know for sure which one I want back. static_cast won't work here as there isn't a method to reconstruct a Variable/Expression from a ResultBase, and more importantly I wouldn't have the original properties of the Variables/Expressions The methods modify some of the properties of the ResultBase and I need those changes to be reflected in the original vectors. (i.e. ResultBase has a property called IsLive, and one of the methods will modify this property. I want this IsLive value to be reflected in the derived class used to create the ResultBase Whats the easiest way to accomplish this?

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• Is there a term for this concept, and does it exist in a static-typed language?

  - by Strilanc

  Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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• Java method introspection from JRuby

  - by Colin Curtin

  Is there a way from JRuby to introspect on a Java object and find out its Java-land methods? Like what http://github.com/oggy/looksee provides, but for Java. Or like (someobject).methods - 1.methods This would be nice for just taking a look at what a Java object provides versus the APIDoc for it.

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• ReSharper conventions for names of event handlers.

  - by Belousov Pavel

  Hello, When I add new event handler for any event, VS creates method like Button_Click. But ReSharper underlines this method as Warning, because all methods should not have any delimeters such as "_". How can I customize rules of ReSharper so that it doesn't underline such methods? Or may be I should rename such methods? Thanks in advance.

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• Grails unit testing domain classes with Set properties - is this safe?

  - by Ali G

  I've created a domain class in Grails like this: class MyObject { static hasMany = [tags: String] // Have to declare this here, as nullable constraint does not seem to be honoured Set tags = new HashSet() static constraints = { tags(nullable: false) } } Writing unit tests to check the size and content of the MyObject.tags property, I found I had to do the following: assertLength(x, myObject.tags as Object[]) assertEquals(new HashSet([...]), myObject.tags) To make the syntax nicer for writing the tests, I implemented the following methods: void assertEquals(List expected, Set actual) { assertEquals(new HashSet(expected), actual) } void assertLength(int expected, Set set) { assertLength(expected, set as Object[]) } I can now call the assertLength() and assertEquals() methods directly on an instance of Set, e.g. assertLength(x, myObject.tags) assertEquals([...], myObject.tags) I'm new to Groovy and Grails, so unaware how dangerous method overloading like this is. Is it safe? If so, I'm slightly* surprised that these methods (or similar) aren't already available - please let me know if they are. * I can see how these methods could also introduce ambiguity if people weren't expecting them. E.g. assertLength(1, set) always passes, no matter what the content of set

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• Does Qt support virtual pure slots ?

  - by ereOn

  Hi, My GUI project in Qt has a lot of "configuration pages" classes which all inherit directly from QWidget. Recently, I realized that all these classes share 2 commons slots (loadSettings() and saveSettings()). Regarding this, I have two questions: Does it make sense to write a intermediate base abstract class (lets name it BaseConfigurationPage) with these two slots as virtual pure methods ? (Every possible configuration page will always have these two methods, so I would say "yes") Before I do the heavy change in my code (if I have to) : does Qt support virtual pure slots ? Is there anything I should be aware of ? Here is a code example describing everything: class BaseConfigurationPage : public QWidget { // Some constructor and other methods, irrelevant here. public slots: virtual void loadSettings() = 0; virtual void saveSettings() = 0; }; class GeneralConfigurationPage : public BaseConfigurationPage { // Some constructor and other methods, irrelevant here. public slots: void loadSettings(); void saveSettings(); };

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• Writing a synchronized thread-safety wrapper for NavigableMap

  - by polygenelubricants

  java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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• Example of contravariance

  - by Misha

  I am thinking of the following example to illustrate why contravariance is useful. Let's consider a GUI framework with Widgets, Events, and Event Listeners. abstract class Event; class KeyEvent extends Event class MouseEvent extends Event trait EventListener[-Event] { def listen(e:Event) } Let Widgets define the following methods: def addKeyEventListener(listener:EventListener[KeyEvent]) def addMouseEventListener(listener:EventListener[MouseEvent]) These methods accept only "specific" event listeners, which is fine. However I would like to define also "kitchen-sink" listeners, which listen to all events, and pass such listeners to the "add listener" methods above. For instance, I would like to define LogEventListener to log all incoming events class LogEventListener extends EventListener[Event] { def listen(e:Event) { log(event) } } Since the trait EventListener is contravariant in Event we can pass LogEventListener to all those "add listener" methods without losing their type safety. Does it make sense ?

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• In Emacs, how can I use imenu more sensibly with C#?

  - by Cheeso

  I've used emacs for a long time, but I haven't been keeping up with a bunch of features. One of these is speedbar, which I just briefly investigated now. Another is imenu. Both of these were mentioned in in-emacs-how-can-i-jump-between-functions-in-the-current-file? Using imenu, I can jump to particular methods in the module I'm working in. But there is a parse hierarchy that I have to negotiate before I get the option to choose (with autocomplete) the method name. It goes like this. I type M-x imenu and then I get to choose Using or Types. The Using choice allows me to jump to any of the using statements at the top level of the C# file (something like imports statements in a Java module, for those of you who don't know C#). Not super helpful. I choose Types. Then I have to choose a namespace and a class, even though there is just one of each in the source module. At that point I can choose between variables, types, and methods. If I choose methods I finally get the list of methods to choose from. The hierarchy I traverse looks like this; Using Types Namespace Class Types Variables Methods method names Only after I get to the 5th level do I get to select the thing I really want to jump to: a particular method. Imenu seems intelligent about the source module, but kind of hard to use. Am I doing it wrong?

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