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  • Javascript object encapsulation that tracks changes

    - by Raynos
    Is it possible to create an object container where changes can be tracked Said object is a complex nested object of data. (compliant with JSON). The wrapper allows you to get the object, and save changes, without specifically stating what the changes are Does there exist a design pattern for this kind of encapsulation Deep cloning is not an option since I'm trying to write a wrapper like this to avoid doing just that. The solution of serialization should only be considered if there are no other solutions. An example of use would be var foo = state.get(); // change state state.update(); // or state.save(); client.tell(state.recentChange()); A jsfiddle snippet might help : http://jsfiddle.net/Raynos/kzKEp/ It seems like implementing an internal hash to keep track of changes is the best option. [Edit] To clarify this is actaully done on node.js on the server. The only thing that changes is that the solution can be specific to the V8 implementation.

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  • Object Events, how do are they implemented

    - by Malfist
    Events are really awesome, and I wouldn't know what I would do without them, but they're a mystery to me. I'm talking about events in a sense, a function(s) is called if a property, or value, a special event happens. I have only the vaguest idea how these actually work. I know it's an observer pattern, but I don't truly know how it works and/or how to implement it. Can someone explain that to me?

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  • Elegant and 'correct' multiton implementation in Objective C?

    - by submachine
    Would you call this implementation of a multiton in objective-c 'elegant'? I have programmatically 'disallowed' use of alloc and allocWithZone: because the decision to allocate or not allocate memory needs to be done based on a key. I know for sure that I need to work with only two instances, so I'm using 'switch-case' instead of a map. #import "Multiton.h" static Multiton *firstInstance = nil; static Multiton *secondInstance = nil; @implementation Multiton + (Multiton *) sharedInstanceForDirection:(char)direction { return [[self allocWithKey:direction] init]; } + (id) allocWithKey:(char)key { return [self allocWithZone:nil andKey:key]; } + (id)allocWithZone:(NSZone *)zone andKey:(char)key { Multiton **sharedInstance; @synchronized(self) { switch (key) { case KEY_1: sharedInstance = &firstInstance; break; case KEY_2: sharedInstance = &secondInstance; break; default: [NSException raise:NSInvalidArgumentException format:@"Invalid key"]; break; } if (*sharedInstance == nil) *sharedInstance = [super allocWithZone:zone]; } return *sharedInstance; } + (id) allocWithZone:(NSZone *)zone { //Do not allow use of alloc and allocWithZone [NSException raise:NSObjectInaccessibleException format:@"Use allocWithZone:andKey: or allocWithKey:"]; return nil; } - (id) copyWithZone:(NSZone *)zone { return self; } - (id) retain { return self; } - (unsigned) retainCount { return NSUIntegerMax; } - (void) release { return; } - (id) autorelease { return self; } - (id) init { [super init]; return self; } PS: I've not tried out if this works as yet, but its compiling cleanly :)

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  • Repository Pattern Standardization of methods

    - by Nix
    All I am trying to find out the correct definition of the repository pattern. My original understanding was this (extremely dubmed down) Separate your Business Objects from your Data Objects Standardize access methods in data access layer. I have really seen 2 different implementations. Implementation 1 : public Interface IRepository<T>{ List<T> GetAll(); void Create(T p); void Update(T p); } public interface IProductRepository: IRepository<Product> { //Extension methods if needed List<Product> GetProductsByCustomerID(); } Implementation 2 : public interface IProductRepository { List<Product> GetAllProducts(); void CreateProduct(Product p); void UpdateProduct(Product p); List<Product> GetProductsByCustomerID(); } Notice the first is generic Get/Update/GetAll, etc, the second is more of what I would define "DAO" like. Both share an extraction from your data entities. Which I like, but i can do the same with a simple DAO. However the second piece standardize access operations I see value in, if you implement this enterprise wide people would easily know the set of access methods for your repository. Am I wrong to assume that the standardization of access to data is an integral piece of this pattern ? Rhino has a good article on implementation 1, and of course MS has a vague definition and an example of implementation 2 is here.

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  • Design patter for extending Android's activities?

    - by Carl
    While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth. What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?

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  • Doubleton Pattern Implementation

    - by Pierreten
    I'm leveraging the Doubleton Pattern from this link http://www.codeproject.com/KB/architecture/designpattern_doubleton.aspx in my own code. I think it makes things a lot easier since the Singleton only provides one instance, but I get two with this pattern. I was wondering if it would make sense to have it implement an interface so I can inject it into my domain layer.

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  • Wicket: Where to add components? Constructor? Or onBeforeRender?

    - by gmallett
    I'm a Wicket newb. This may just be my ignorance of the Wicket lifecycle so please enlighten me! My understanding is that Wicket WebPage objects are instantiated once and then serialized. This has led to a point of confusion for me, see below. Currently I have a template class which I intend to subclass. I followed the example in the Wicket docs demonstrating how to override the template's behavior in the subclass: protected void onBeforeRender() { add(new Label("title", getTitle())); super.onBeforeRender(); } protected String getTitle() { return "template"; } Subclass: protected String getTitle() { return "Home"; } This works very well. What's not clear to me are the "best practices" for this. It seems like onBeforeRender() is called on every request for the page, no? This seems like there would be substantially more processing done on a page if everything is in onBeforeRender(). I could easily follow the example of the other Wicket examples and add some components in the constructor that I do not want to override, but then I've divided by component logic into two places, something I'm hesitant to do. If I add a component that I intend to be in all subclasses, should I add it to the constructor or onBeforeRender()?

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  • Separating data from the UI code with Linq to SQL entities

    - by Sir Psycho
    If it's important to keep data access 'away' from business and presentation layers, what alternatives or approaches can I take so that my LINQ to SQL entities can stay in the data access layer? So far I seem to be simply duplicating the classes produced by sqlmetal, and passing those object around instead simply to keep the two layers appart. For example, I have a table in my DB called Books. If a user is creating a new book via the UI, the Book class generated by sqlmetal seems like a perfect fit although I'm tightly coupling my design by doing so.

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  • How to proxy calls to the instance of an object

    - by mr.b
    Edit: Changed question title from "Does C# allow method overloading, PHP style (__call)?" - figured out it doesn't have much to do with actual question. Also edited question text. What I want to accomplish is to proxy calls to a an instance of an object methods, so I could log calls to any of its methods. Right now, I have code similar to this: class ProxyClass { static logger; public AnotherClass inner { get; private set; } public ProxyClass() { inner = new AnotherClass(); } } class AnotherClass { public void A() {} public void B() {} public void C() {} // ... } // meanwhile, in happyCodeLandia... ProxyClass pc = new ProxyClass(); pc.inner.A(); // need to write log message like "method A called" pc.inner.B(); // need to write log message like "method B called" // ... So, how can I proxy calls to an object instance in extensible way? Method overloading would be most obvious solution (if it was supported in PHP way). By extensible, meaning that I don't have to modify ProxyClass whenever AnotherClass changes. In my case, AnotherClass can have any number of methods, so it wouldn't be appropriate to overload or wrap all methods to add logging. I am aware that this might not be the best approach for this kind of problem, so if anyone has idea what approach to use, shoot. Thanks!

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  • Android::Creating a clickable collage?

    - by Legend
    I am trying to create something like a rectangular grid with pictures. When a picture is clicked, it should zoom in pushing the other ones out. I don't know what you name you call this particular model with but does anyone have suggestions on where I should start? Collage Example

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  • What do you call the concept of dynamic data definition?

    - by DJTripleThreat
    Maybe this is simpler and more straightforward then what I'm thinking but I can't seem to find this concept on google anywhere. The concept is this: You have a table in a database and the table has a specified number of columns. However, it has been asked of me by previous clients that there also be a set of dynamic user defined columns that can be added on the fly. What is this concept called and is it considered a design pattern?

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  • I'd want a method to be called only by objects of a specific class

    - by mp
    Suppose you have this class: public class A { private int number; public setNumber(int n){ number = n; } } I'd like the method setNumber could be called only by objects of a specific class. Does it make sense? I know it is not possible, is it? Which are the design alternatives? Some well known design pattern? Sorry for the silly question, but I'm a bit rusty in OO design.

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  • Using Remote Web Page to Initialize iPhone App

    - by Chris_K
    My iPhone app relies on a vendor's XML feed to provide data. But that feed is not locked down. The vendor could change the format of the XML at any time, although so far they've promised not to. Since I might want to tell my app to use a different URL for its data source, I'd like to set up a single "Command Central" Web page, on my own server, to direct the app to the correct data source. In other words, each time my app starts, in the background and unseen by the user, it would visit "http://www.myserver.com/iphoneapp_data_sources.xml" to retrieve the URL for retrieving data from my vendor. That way, if my vendor suddenly changes the exact URL or the XML feed that the app needs, I can update that Web page and ensure that all installations of the app are using the correct XML feed. Does anyone have any advice or examples showing this kind of approach? It seems as if this must be a common problem, but so far I haven't found a well-established design pattern that fits it.

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  • Makefile: expand dependencies

    - by Danyel
    First off, the title is very generic because there are just tons of ways of how to possibly solve this. However, I'm looking for a clean and neat way. Situation: I have two equal object files foo.o and foo-pi.o, the latter of which is position-independent (compiled with -fPIC). Both depend on foo.h and bar.h. Problem: How do I, without code duplication, declare dependency of all foo*.o to bar.h? Solutions so far: $(shell bash -c 'echo -ne foo{-pi,}.o'}: bar.h $(addsuffix .o, $(addprefix fo, o-pi o)): bar.h The first solution is not portable on systems that don't support bash, the second is a dirty solution since I could not figure out how to use empty strings in addprefix.

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  • Is Embed Resource a good approach for a read only xml database?

    - by Nasser Hajloo
    I have an open source application (here) This application get a character or a sentence and give some unicode information about it. Iuse Unicode Character Database which provided by Unicode.org this is a XML document (130MB) At first I embed this XML to my DLL but I don't know is it a good approach or no. because DLL size growth just because of this XML document. I can use it like any other resources but usercan see it. What Should I do? What is the best pattern for this? and Why ? TIA

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  • Instantiate a javascript module only one time.

    - by Cedric Dugas
    Hey guys, I follow a module pattern where I instantiate components, however, a lot of time a component will only be instantiate one time (example: a comment system for an article). For now I instantiate in the same JS file. but I was wondering if it is the wrong approach? It kind of make no sense to instantiate in the same file and always only once. But at the same time, if this file is in the page I want to have access to my module without instantiate from elsewhere, and IF I need another instance, I just create another from elsewhere... Here is the pattern I follow: ApplicationNamespace.Classname = function() { // constructor function privateFunctionInit() { // private } this.privilegedFunction = function() { // privileged privateFunction(); }; privateFunctionInit() }; ApplicationNamespace.Classname.prototype = { Method: function(){} } var class = new ApplicationNamespace.Classname(); What do you think, wrong approach, or is this good?

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  • How to write this in better way?

    - by dario
    Hi all. Let's look at this code: IList<IHouseAnnouncement> list = new List<IHouseAnnouncement>(); var table = adapter.GetData(); //get data from repository object -> DataTable if (table.Rows.Count >= 1) { for (int i = 0; i < table.Rows.Count-1; i++) { var anno = new HouseAnnouncement(); anno.Area = float.Parse(table.Rows[i][table.powierzchniaColumn].ToString()); anno.City = table.Rows[i][table.miastoColumn].ToString(); list.Add(anno); } } return list; Is it better way to write this in less code and better fashion (must be :-) )? Maybe using labda (but let mi know how)? Thanks in advance!

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  • Magic Method __set() on a Instanciated Object

    - by streetparade
    Ok i have a problem, sorry if i cant explaint it clear but the code speaks for its self. i have a class which generates objects from a given class name; Say we say the class is Modules: public function name($name) { $this->includeModule($name); try { $module = new ReflectionClass($name); $instance = $module->isInstantiable() ? $module->newInstance() : "Err"; $this->addDelegate($instance); } catch(Exception $e) { Modules::Name("Logger")->log($e->getMessage()); } return $this; } The AddDelegate Method: protected function addDelegate($delegate) { $this->aDelegates[] = $delegate; } The __call Method public function __call($methodName, $parameters) { $delegated = false; foreach ($this->aDelegates as $delegate) { if(class_exists(get_class($delegate))) { if(method_exists($delegate,$methodName)) { $method = new ReflectionMethod(get_class($delegate), $methodName); $function = array($delegate, $methodName); return call_user_func_array($function, $parameters); } } } The __get Method public function __get($property) { foreach($this->aDelegates as $delegate) { if ($delegate->$property !== false) { return $delegate->$property; } } } All this works fine expect the function __set public function __set($property,$value) { //print_r($this->aDelegates); foreach($this->aDelegates as $k=>$delegate) { //print_r($k); //print_r($delegate); if (property_exists($delegate, $property)) { $delegate->$property = $value; } } //$this->addDelegate($delegate); print_r($this->aDelegates); } class tester { public function __set($name,$value) { self::$module->name(self::$name)->__set($name,$value); } } Module::test("logger")->log("test"); // this logs, it works echo Module::test("logger")->path; //prints /home/bla/test/ this is also correct But i cant set any value to class log like this Module::tester("logger")->path ="/home/bla/test/log/"; The path property of class logger is public so its not a problem of protected or private property access. How can i solve this issue? I hope i could explain my problem clear.

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  • Design pattern: Polymorphism for list of objects

    - by ziang
    Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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  • which design choose? - pros and cons

    - by Guarava Makanili
    Which of these 3 approches would choose and why? // This is the one I would choose class Car { } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem might be when we use ORM framework and we try to invoke save with parameter Car class Car { private FeeCalculator calculator; public double calculateFee() { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem mentioned above is solved, but I don't like this design class Car { public double calculateFee(FeeCalculator calculator) { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } }

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  • How to handle request/response propagation up and down a widget hierarchy in a GUI app?

    - by fig-gnuton
    Given a GUI application where widgets can be composed of other widgets: If the user triggers an event resulting in a lower level widget needing data from a model, what's the cleanest way to be able to send that request to a controller (or the datastore itself)? And subsequently get the response back to that widget? Presumably one wouldn't want the controller or datastore to be a singleton directly available to all levels of widgets, or is this an acceptable use of singleton? Or should a top level controller be injected as a dependency through a widget hierarchy, as far down as the lowest level widget that might need that controller? Or a different approach entirely?

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  • commad design pattern usage

    - by sagie
    Hi. I've read 3 descriptions of the command design pattern: wikipedia, dofactory and source making. In all of them, the UML shows a relation between the client to the receiver & the concrete command, but no relation to the invoker. But in all 3 examples the client is the one that initiates the invoker and call its Execute method. I think that should be a relation to the invoker as well. Am I missing somthing in here? Maybe even a basic UML knowladge?

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  • Persistance Queue Implementation

    - by Winter
    I was reading an article on Batch Processing in java over at JDJ http://java.sys-con.com/node/415321 . The article mentioned using a persistence queue as a Batch Updater instead of immediately sending an individual insert or update to the database. The author doesn't give a concrete example of this concept so I googled Persistence Queue but that didn't come up with much. Does anyone know of a good example of this?

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