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  • Object Oriented Programming in AS3

    - by Jordan
    I'm building a game in as3 that has balls moving and bouncing off the walls. When the user clicks an explosion appears and any ball that hits that explosion explodes too. Any ball that then hits that explosion explodes and so on. My question is what would be the best class structure for the balls. I have a level system to control levels and such and I've already come up with working ways to code the balls. Here's what I've done. My first attempt was to create a class for Movement, Bounce, Explosion and finally Orb. These all extended each other in the order I just named them. I got it working but having Bounce extend Movement and Explosion extend Bounce, it just doesn't seem very object oriented because what if I wanted to add a box class that didn't move, but did explode? I would need a separate class for that explosion. My second attempt was to create Movement, Bounce and Explosion without extending anything. Instead I passed in a reference to the Orb class to each. Then the class stores that reference and does what it needs to do based on events that are dispatched by the Orb such as update, which was broadcast from Orb every enter frame. This would drive the movement and bounce and also the explosion when the time came. This attempt worked as well but it just doesn't seem right. I've also thought about using Interfaces but because they are more of an outline for classes, I feel like code reuse goes out the window as each class would need its own code for a specific task even if that task is exactly the same. I feel as if I'm searching for some form of multiple inheritance for classes that as3 does not support. Can someone explain to me a better way of doing what I'm attempting to do? Am I being to "Object Oriented" by having classed for Movement, Bounce, Explosion and Orb? Are Interfaces the way to go? Any feedback is appreciated!

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  • How do I add and remove an event listener using a function with parameters?

    - by Bungle
    Sorry if this is a common question, but I couldn't find any answers that seemed pertinent through searching. If I attach an event listener like this: window.addEventListener('scroll', function() { check_pos(box); }, false); it doesn't seem to work to try to remove it later, like this: window.removeEventListener('scroll', function() { check_pos(box); }, false); I assume this is because the addEventListener and removeEventListener methods want a reference to the same function, while I've provided them with anonymous functions, which, while identical in code, are not literally the same. How can I change my code to get the call to removeEventListener to work? The "box" argument refers to the name of an <iframe> that I'm tracking on the screen; that is, I want to be able to subscribe to the scroll event once for each <iframe> that I have (the quantity varies), and once the check_pos() function measures a certain position, it will call another function and also remove the event listener to free up system resources. My hunch is that the solution will involve a closure and/or naming the anonymous function, but I'm not sure exactly what that looks like, and would appreciate a concrete example. Hope that makes sense. Thanks for any help!

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  • MySQL multidimensional arrays...

    - by jay
    What is the best way to store data that is dynamic in nature using MySQL? Let's say I have a table in which one item is "dynamic". For some entries I need to store one value, but for others it could be one hundred values. For example let's say I have the following simple table: CREATE TABLE manager ( name char(50), worker_1_name(50), worker_2_name(50), ... worker_N_name(50) ); Clearly, this is not an ideal way to set up a database. Because I have to accommodate the largest group that a manager could potentially have, I am wasting a lot of space in the database. What I would prefer is to have a table that I can use as a member of another table (like I would do in C++ through inheritance) that can be used by the "manager" table to handle the variable number of employees. It might look something like this. CREATE TABLE manager ( name char(50), underlings WORKERS ); CREATE TABLE WORKERS ( name char(50), ); I would like to be able to add a variable number of workers to each manager. Is this possible or am I constrained to enumerating all the possible number of employees even though I will use the full complement only rarely?

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  • Am I abusing Policies?

    - by pmr
    I find myself using policies a lot in my code and usually I'm very happy with that. But from time to time I find myself confronted with using that pattern in situations where the Policies are selected and runtime and I have developed habbits to work around such situations. Usually I start with something like that: class DrawArrays { protected: void sendDraw() const; }; class DrawElements { protected: void sendDraw() const; }; template<class Policy> class Vertices : public Policy { using Policy::sendDraw(); public: void render() const; }; When the policy is picked at runtime I have different choices of working around the situation. Different code paths: if(drawElements) { Vertices<DrawElements> vertices; } else { Vertices<DrawArrays> vertices; } Inheritance and virtual calls: class PureVertices { public: void render()=0; }; template<class Policy> class Vertices : public PureVertices, public Policy { //.. }; Both solutions feel wrong to me. The first creates an umaintainable mess and the second introduces the overhead of virtual calls that I tried to avoid by using policies in the first place. Am I missing the proper solutions or do I use the wrong pattern to solve the problem?

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  • Use AJAX to reload captcha

    - by arik-so
    Hello! This question may have been asked already - but unfortunately, I could not find any satisfactory answers. I will just ask it for my concrete case and ask the admins not to delete the question for at least a few days so I can try it out... I have a page. It uses a captcha. Like so: <?php session_start(); // the captcha saves the md5 into the session ?> <img src="captcha.php" onclick="this.src = this.src" /> That was my first code. It did not work, because the browser condsidered it useless to reload an image if the source is the same. My current solution is to pass a get parameter: onclick="this.src = 'captcha.php?randomNumber='+ranNum" The JavaScript variable var ranNum is generated randomly every time the onclick event fires. It works fine, still, I don't like the possibility, if the - though improbable - case of two numbers being the same twice in a row. Although the random number varies between -50,000 and 50,000 - I still do not like it. And I don't think the method is right. I would like to know the 'righter' method, by means of AJAX. I know it's possible. I hope you know how it's possible ^^ In that case, please show me. Thanks in advance! By the way - if I spell cap(t)cha differently, never mind, the reference to the PHP file is right in my code: I use randomImage.php

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  • How to prevent linq-to-sql designer undo my changing

    - by anonim.developer
    Dear All, Thanks for your attention in advance, I’ve met an issue with LINQ-2-SQL designer in VS 2008 SP1 which has made me CRAZY. I use Linq2sql as my DAL. It seems Linq2sql speeds up coding in the first step but lots of issues arise in feature specifically with table or object inheritance. In this case I have a class Entity that all other entity classes generated by Linq2sql designer inherit from. public abstract class Entity { public virtual Guid ID { get; protected set; } } public partial class User : monius.Data.Entity { } And the following generated by L2S designer (DataModel.designer.cs) [Column(Storage = "_ID", AutoSync = AutoSync.OnInsert, DbType = "UniqueIdentifier NOT NULL", IsPrimaryKey = true, IsDbGenerated = true, UpdateCheck = UpdateCheck.Never)] [DataMember(Order = 1)] public System.Guid ID { get { return this._ID; } set { if ((this._ID != value)) { this.OnIDChanging(value); this.SendPropertyChanging(); this._ID = value; this.SendPropertyChanged("ID"); this.OnIDChanged(); } } } When I compile the code VS warns me that Warning 1 'User.ID' hides inherited member 'Entity.ID'. To make the current member override that mplementation, add the override keyword. Otherwise add the new keyword. That warning is obvious and I have to change the code generated by L2S designer (DataModel.designer.cs) to […] public override System.Guid ID { … protected set … } And the code compiled with no error or warning and everyone is happy. But that is not the end of story. As soon as I made changes to entities of the diagram (dbml) or even I open dbml file to view it, any change manually I made to designer has been vanished and POOF! Redo AGAIN. That is a painful job. Now I wonder if there is a way to force L2S designer not changing portions of auto-generated code. I’ll be appreciated if someone kindly helps me with this issue.

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  • How to inherit from a non-prototype object

    - by Andres Jaan Tack
    The node-binary binary parser builds its object with the following pattern: exports.parse = function parse (buffer) { var self = {...} self.tap = function (cb) {...}; self.into = function (key, cb) {...}; ... return self; }; How do I inherit my own, enlightened parser from this? Is this pattern designed intentionally to make inheritance awkward? My only successful attempt thus far at inheriting all the methods of binary.parse(<something>) is to use _.extend as: var clever_parser = function(buffer) { if (this instanceof clever_parser) { this.parser = binary.parse(buffer); // I guess this is super.constructor(...) _.extend(this.parser, this); // Really? return this.parser; } else { return new clever_parser(buffer); } } This has failed my smell test, and that of others. Is there anything about this that makes in tangerous?

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  • Active Record two belongs_to calls to the same model

    - by ethyreal
    In linking a sports event to two teams, at first this seemed to make since: events - id:integer - integer:home_team_id - integer:away_team_id teams - integer:id - string:name However I am troubled by how I would link that up in the active record model: class Event belongs_to :home_team, :class_name => 'Team', :foreign_key => "home_team_id" belongs_to :away_team, :class_name => 'Team', :foreign_key => "away_team_id" end Is that the best solution? In an answer to a similar question I was pointed to single table inheritance, and then later found polymorphic associations. Neither of which seemed to fit this association. Perhaps I am looking at this wrong, but I see no need to subclass a team into home and away teams since the distinction is only in where the game is played. I thought also about a has_many through association but that seems two much as I will only ever need two teams, but those two teams don't belong to any one event. event_teams - integer:event_id - integer:team_id - boolean:is_home Is there a cleaner more semantic way for making these associations in active record? Thanks

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  • How do I access the CodeDomProvider from a class inheriting from Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite?

    - by Charlie
    Does anyone know how to get a CodeDomProvider in the new Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite from the Visual Studio 2010 SDK? I used to get access to it just by in mere inheritance of the class Microsoft.CustomTool.BaseCodeGeneratorWithSite, but now with this new class it is not there. I see a GlobalServiceProvider and a SiteServiceProvider but I can't find any example on how to use them. Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite: http://msdn.microsoft.com/en-us/library/bb932625.aspx I was to do this: public class Generator : Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite { public override string GetDefaultExtension() { // GetDefaultExtension IS ALSO NOT ACCESSIBLE... return this.InputFilePath.Substring(this.InputFilePath.LastIndexOf(".")) + ".designer" + base.GetDefaultExtension(); } // This method is being called every time the attached xml is saved. protected override byte[] GenerateCode(string inputFileName, string inputFileContent) { try { // Try to generate the wrapper file. return GenerateSourceCode(inputFileName); } catch (Exception ex) { // In case of a faliure - print the exception // as a comment in the source code. return GenerateExceptionCode(ex); } } public byte[] GenerateSourceCode(string inputFileName) { Dictionary<string, CodeCompileUnit> oCodeUnits; // THIS IS WHERE CodeProvider IS NOT ACCESSIBLE CodeDomProvider oCodeDomProvider = this.CodeProvider; string[] aCode = new MyCustomAPI.GenerateCode(inputFileName, ref oCodeDomProvider); return Encoding.ASCII.GetBytes(String.Join(@" ", aCode)); } private byte[] GenerateExceptionCode(Exception ex) { CodeCompileUnit oCode = new CodeCompileUnit(); CodeNamespace oNamespace = new CodeNamespace("System"); oNamespace.Comments.Add(new CodeCommentStatement(MyCustomAPI.Print(ex))); oCode.Namespaces.Add(oNamespace); string sCode = null; using (StringWriter oSW = new StringWriter()) { using (IndentedTextWriter oITW = new IndentedTextWriter(oSW)) { this.CodeProvider.GenerateCodeFromCompileUnit(oCode, oITW, null); sCode = oSW.ToString(); } } return Encoding.ASCII.GetBytes(sCode ); } } Thanks for your help!

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  • WPF View/ViewModels using Generics- how?

    - by Investor5555
    New to WPF, so please bear with me... Suppose I have 2 tables in SQL Thing OtherThing Both have the exact same fields: ID (int) Name (string) Description (string) IsActive (bit/bool) DateModified (DateTime) So, I want to create one Model (not two) and do something like this: BaseModel<T>() { public int ID {get;set;} ... } etc. (of course, using the INotifyPropertyChanged, just trying to keep the code simple). I want to be able to create a BaseView and BaseViewModel that would work with whatever model conforms to the Thing/OtherThing. I am really at a loss as to what to do here to make this generic, so I don't have to have a ThingView/ThingViewModel and a OtherThingView/OtherThingViewModel... It seems that this should be simple, but I cannot seem to figure it out. Does anyone have a code example where they could interchange various items from a dropdown list using one view, one ViewModel, and one base datamodel (and switching out the type from a dropdown)? For example, a combobox has 3 identical table structures for Thing OtherThing SomeThing and on selection changed, I want to pull the data from whatever table was selected, to be able to do standard CRUD operations on any of these 3 tables, without having to create concrete classes for each view/viewmodel.

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  • Magic Methods in Python

    - by dArignac
    Howdy, I'm kind of new to Python and I wonder if there is a way to create something like the magic methods in PHP (http://www.php.net/manual/en/language.oop5.overloading.php#language.oop5.overloading.methods) My aim is to ease the access of child classes in my model. I basically have a parent class that has n child classes. These classes have three values, a language key, a translation key and a translation value. The are describing a kind of generic translation handling. The parent class can have translations for different translation key each in different languages. E.g. the key "title" can be translated into german and english and the key "description" too (and so far and so on) I don't want to get the child classes and filter by the set values (at least I want but not explicitly, the concrete implementation behind the magic method would do this). I want to call parent_class.title['de'] # or also possible maybe parent_class.title('de') for getting the translation of title in german (de). So there has to be a magic method that takes the name of the called method and their params (as in PHP). As far as I dug into Python this is only possible with simple attributes (_getattr_, _setattr_) or with setting/getting directly within the class (_getitem_, _setitem_) which both do not fit my needs. Maybe there is a solution for this? Please help! Thanks in advance!

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  • Libraries and pseudocode for physical Dashboard/Status board

    - by dani
    OK, so I bought a 46" screen for the office yesterday, and with the imminent risk of being accused for setting up an "elaborate World Cup procrastination scheme", I'd better show my colleagues what it's meant for ;) Looking at my simple sketch, and at these great projects from which I was inspired, I would like to get some input on the following: Pseudocode for the skeleton: As some methods should be called every 24 hours ("Today's date in the heading"), others at 60 second intervals ("Twitter results"), what would be a good approach using JavaScript (jQuery) and PHP? EDIT: Alsciende: I can agree that #1 and #8 are too vague. Therefore I remove #8 and try to clarify #1: With "Pseudocode for the skeleton", I basically mean could this be done entirely using JavaScript timers and how would you set up the various timers? Library for Google Analytics: Which libraries support the Google Analytics API and can produce neat charts. Preferably HTML5, JavaScript-based like Protovis. Library for Twitter: Which libraries would you recommend for fetching twitter search results and latest tweets from profiles. Libraries for Typography/CSS/HTML5: Trying to learn some HTML5 etc. in the process, please advice on any other typography/css libraries that could be of relevance. Scraping/Parsing? I'll give you a concrete example: Trying to fetch today's menu from this restaurant's website, how would you go about? (it's in Swedish - but you get the point - sorry ;) ) Real-time stats? I'm using the WassUp-plugin for WordPress to track real-time visitors on our website. Other logging software (AWStats etc.) is probably also installed on the webserver. Any ideas on how to extract information from these and present in real-time on the dashboard? Browser choice? Which Browser and OS would you pick? Stable, Full-screen, HTML5.

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  • CQRS and email notification

    - by t0PPy
    Reading up on CQRS there is a lot of talk of email notification - i'm wondering where to get the data from. Imagine a senario where one user invites other users to an event. To inform a user that he has been invitet to an event, he is send an email. The concrete mecanics might go like this: A "CreateEvent" command with an associated collection of user to invite, is received by the server. A new meeting aggregate is created and a method "InviteUser" is called for each user that is to be invited. Each time a user is invited to an event, a domain event "UserWasInvitedToEvent" is raised. An email notification sender picks up the domain event and sends out the notification email. Now my question is this: Where do i go for information to include in the email? Say i want to include a description of the event as well as the users name. Since this is CQRS i can't get it thru my domain model; All the properties of the domain objects are private! Should i then query the write side? Or maybe move email notification to a different service entirely? Any thoughts will be much appriciated!

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  • Client Web Browser Behavior When Handling 301 Redirect

    - by Jon Swanson
    The RFC seems to suggest that the client should permanently cache the response: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html 10.3.2 301 Moved Permanently The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible. This response is cacheable unless indicated otherwise. The new permanent URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s). If the 301 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued. Note: When automatically redirecting a POST request after receiving a 301 status code, some existing HTTP/1.0 user agents will erroneously change it into a GET request. I'm having a hard time finding concrete browser documentation for any major browser that states how they handle these. I've started digging through the source code of firefox, but quickly got lost. Is the following scenario true for which (if any) browsers, and is there definitive documentation for either Firefox or IE that states as much?: First Time Around: 1.1: User enters link to site A, or clicks on a link directed at Site A 1.2: Browser interprets link at Site A, first time, no cache. Sends GET to Site A. 1.2: Site A responds with 301 Redirect to Site B 1.3: Browser sends GET to Site B. Any Subsequent Times Around: 2.2: User clicks on a link directed at Site A 2.2: Browser sees that, due to a past 301 redirect, Site A should now be Site B. 2.3: Without initiating any request whatsoever at Site A, browser initiates GET at Site B.

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  • WCF ServiceContract and svcutil issue

    - by Valko
    Hi, I have a public interface auto-generated bu svcutil: [System.ServiceModel.ServiceContractAttribute(Namespace="...", ConfigurationName="...")] public interface MyInterface Then I have asmx web service inheriting it and working fine. I am trying ot convert it to WCF but when I instrument the service (in asmx.cs code behind) with ServiceContract: [ServiceContract(Namespace = "...")] public class MyService : MyInterface Also I have cerated .svc file and added the system.serviceModel setting in the config file. The goal is to migrate the asmx service to WCF service. I've got this error: The service class of type MyService both defines a ServiceContract and inherits a ServiceContract from type MyInterface. Contract inheritance can only be used among interface types. If a class is marked with ServiceContractAttribute, it must be the only type in the hierarchy with ServiceContractAttribute. The asmx service is still working fine. Only the .svc is giving me issues. My question is how to fix that. MyInterface is an interface so I do not see what the problem is and why I've got the error anyway. Note I do not want to change MyInterface, because it is autogenerated from svcutil from my wsdl schema and I do not want this interface to be edited manually. The whole idea is to have the service types automatically genereted from WSDL and to save my team development efforts with manual editing. Any help is appreciated.

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  • Refactoring exercise with generics

    - by Berryl
    I have a variation on a Quantity (Fowler) class that is designed to facilitate conversion between units. The type is declared as: public class QuantityConvertibleUnits<TFactory> where TFactory : ConvertableUnitFactory, new() { ... } In order to do math operations between dissimilar units, I convert the right hand side of the operation to the equivalent Quantity of whatever unit the left hand side is in, and do the math on the amount (which is a double) before creating a new Quantity. Inside the generic Quantity class, I have the following: protected static TQuantity _Add<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount + equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } protected static TQuantity _Subtract<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount - equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } ... same for multiply and also divide I need to get the typing right for a concrete Quantity, so an example of an add op looks like: public static ImperialLengthQuantity operator +(ImperialLengthQuantity lhs, ImperialLengthQuantity rhs) { return _Add(lhs, rhs); } The question is those verbose methods in the Quantity class. The only change between the code is the math operator (+, -, *, etc.) so it seems that there should be a way to refactor them into a common method, but I am just not seeing it. How can I refactor that code? Cheers, Berryl

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  • What's the boost way to create a functor that binds out an argument

    - by Mordachai
    I have need for a function pointer that takes two arguments and returns a string. I would like to pass an adapter that wraps a function that takes one argument, and returns the string (i.e. discard one of the arguments). I can trivially build my own adapter, that takes the 2 arguments, calls the wrapped function passing just the one argument through. But I'd much rather have a simple way to create an adapter on the fly, if there is an easy way to do so in C++/boost? Here's some details to make this a bit more concrete: typedef boost::function<CString (int,int)> TooltipTextFn; class MyCtrl { public: MyCtrl(TooltipTextFn callback = boost::bind(&MyCtrl::GetCellText, this, _1, _2)) : m_callback(callback) { } // QUESTION: how to trivially wrapper GetRowText to conform to TooltipTextFn by just discarding _2 ?! void UseRowText() { m_callback = boost::bind(&MyCtrl::GetRowText, this, _1, ??); } private: CString GetCellText(int row, int column); CString GetRowText(int row); TooltipTextFn m_callback; } Obviously, I can supply a member that adapts GetRowText to take two arguments and only passes the first to GetRowText() itself. But is there already a boost binder / adapter that lets me do that?

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  • Use XML Layout to contain a simple drawing

    - by user329999
    I would like to create a simple drawing (lines, circles, squares, etc...) but I'm having difficulty figuring out the best way to do this. The drawing would need to be scaled to fit the display since the size is indirectly specified by the user (like in a CAD application). Also, I don't want to take up the entire display, leaving room for some controls (buttons, etc). I would pass the data to describe the drawing. Here's how I imagine it would work. I create an XML layout that contains something that holds the drawing (ImageView, BitmapDrawable, ShapeDrawable, ...??? not sure exactly what). Then in my Activity I would load the main XML and obtain the resource for the control that holds the drawing. I would then draw to a bitmap. Once the bitmap was completed I would load it into the control that is to hold the drawing. Somewhere along this path it would be scaled to fill the entire area allocated for the drawing in the XML layout. I don't know if my approach is the way to do this or what classes to use. I read the http://developer.android.com/guide/topics/graphics/2d-graphics.html documentation, but it's not helping me with an example. The examples I do find leave me with hints, but nothing concrete enough to do what I want, especially when it comes to scaling, using XML and/or having other controls. Also, there seems to be no good documentation on the design of the 2D drawing system in a more conceptual manner, so it makes what I read difficult to put into any useful context. Any hints on what classes would be useful and/or a good example any other reading materials? Thanks

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  • WM_NOTIFY and superclass chaining issue in Win32

    - by DasMonkeyman
    For reference I'm using the window superclass method outlined in this article. The specific issue occurs if I want to handle WM_NOTIFY messages (i.e. for custom drawing) from the base control in the superclass I either need to reflect them back from the parent window or set my own window as the parent (passed inside CREATESTRUCT for WM_(NC)CREATE to the base class). This method works fine if I have a single superclass. If I superclass my superclass then I run into a problem. Now 3 WindowProcs are operating in the same HWND, and when I reflect WM_NOTIFY messages (or have them sent to myself from the parent trick above) they always go to the outermost (most derived) WindowProc. I have no way to tell if they're messages intended for the inner superclass (base messages are supposed to go to the first superclass) or messages intended for the outer superclass (messages from the inner superclass are intended for the outer superclass). These messages are indistinguishable because they all come from the same HWND with the same control ID. Is there any way to resolve this without creating a new window to encapsulate each level of inheritance? Sorry about the wall of text. It's a difficult concept to explain. Here's a diagram. single superclass: SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------/ superclass of a superclass: SuperB::WindowProc() - SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------+-----------------------/ ^--------WM_NOTIFY(A)-----------/ The WM_NOTIFY messages in the second case all come from the same HWND and control ID, so I cannot distinguish between the messages intended for SuperA (from Base) and messages intended for SuperB (from SuperA). Any ideas?

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  • How to create instances of a class from a static method?

    - by Pierre
    Hello. Here is my problem. I have created a pretty heavy readonly class making many database calls with a static "factory" method. The goal of this method is to avoid killing the database by looking in a pool of already-created objects if an identical instance of the same object (same type, same init parameters) already exists. If something was found, the method will just return it. No problem. But if not, how may I create an instance of the object, in a way that works with inheritance? >>> class A(Object): >>> @classmethod >>> def get_cached_obj(self, some_identifier): >>> # Should do something like `return A(idenfier)`, but in a way that works >>> class B(A): >>> pass >>> A.get_cached_obj('foo') # Should do the same as A('foo') >>> A().get_cached_obj('foo') # Should do the same as A('foo') >>> B.get_cached_obj('bar') # Should do the same as B('bar') >>> B().get_cached_obj('bar') # Should do the same as B('bar') Thanks.

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  • Question about decorator pattern and the abstract decorator class?

    - by es11
    This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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  • Calling DI Container directly in method code (MVC Actions)

    - by fearofawhackplanet
    I'm playing with DI (using Unity). I've learned how to do Constructor and Property injection. I have a static container exposed through a property in my Global.asax file (MvcApplication class). I have a need for a number of different objects in my Controller. It doesn't seem right to inject these throught the constructor, partly because of the high quantity of them, and partly because they are only needed in some Actions methods. The question is, is there anything wrong with just calling my container directly from within the Action methods? public ActionResult Foo() { IBar bar = (Bar)MvcApplication.Container.Resolve(IBar); // ... Bar uses a default constructor, I'm not actually doing any // injection here, I'm just telling my conatiner to give me Bar // when I ask for IBar so I can hide the existence of the concrete // Bar from my Controller. } This seems the simplest and most efficient way of doing things, but I've never seen an example used in this way. Is there anything wrong with this? Am I missing the concept in some way?

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  • In Java it seems Public constructors are always a bad coding practice

    - by Adam Gent
    This maybe a controversial question and may not be suited for this forum (so I will not be insulted if you choose to close this question). It seems given the current capabilities of Java there is no reason to make constructors public ... ever. Friendly, private, protected are OK but public no. It seems that its almost always a better idea to provide a public static method for creating objects. Every Java Bean serialization technology (JAXB, Jackson, Spring etc...) can call a protected or private no-arg constructor. My questions are: I have never seen this practice decreed or written down anywhere? Maybe Bloch mentions it but I don't own is book. Is there a use case other than perhaps not being super DRY that I missed? EDIT: I explain why static methods are better. .1. For one you get better type inference. For example See Guava's http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained .2. As a designer of the class you can later change what is returned with a static method. .3. Dealing with constructor inheritance is painful especially if you have to pre-calculate something.

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  • Trying to create XPath from this HTML snippet

    - by doneright
    I have played for a while writing XPath but am unable to come up with exactly what I want. I'm trying to write XPath for link(click1 and click2 in code snippet below) based on known text(myidentity in code snippet below). Can someone take a look into and suggest possible solution? HTML code snippet: <div class="abc"> <a onclick="mycontroller.goto('xx','yy'); return false;" href="#"> <img src="images/controls/inheritance.gif"/> </a> myidentity <span> <a onclick="mycontroller.goto('xx','yy'); return false;" href="#">click1</a> <a onclick="mycontroller.goto('xx','yy'); return false;" href="#">click2</a> </span> </div>

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  • AJAX contact form in CodeIgniter

    - by Ross
    Few questions: I'm using CI and JQuery AJAX. In my code below, I assemble dataString, which by default, is appended to the URL as a query string. I've changed the AJAX "type" to POST, so my question is - how do I access dataString in my CI app? It would seem I still have to use $name=$this->input->post('name') Which to me, makes setting dataString redundant? -- I've tried searching but can't really find anything concrete. Would it be possible to still make use of CIs validation library and AJAX? if($this->form_validation->run() == FALSE) { // what can i return so that my CI app shows errors? } Normally you would reload the contact form or redirect the user. In an ideal world I would like the error messages to be shown to the user. Jquery: $(document).ready(function($){ $("#submit_btn").click(function(){ var name = $("input#name").val(); var company = $("input#company").val(); var email = $("input#email").val(); var phone = $("input#phone").val(); var message = $("textarea#message").val(); var dataString = 'name=' + name + '&message=' + message + '&return_email=' + email + '&return_phone=' + phone + '&company=' + company; var response = $.ajax({ type: "POST", url: "newsite/contact_ajax/", data: dataString }).responseText; //$('#contact').hide(); //$('#contact').html('<h5>Form submitted! Thank you!</h5><h4>We will be in touch with you soon.</h4>'); //$('#contact').fadeIn('slow'); return false; }); }); hope i've been clear enough - if anyone has a decent example of a CI contact form that would be great. there's mixed stuff on the internet but nothing that hits all the boxes. thanks

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