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  • Naming methods that do the same thing but return different types

    - by Konstantin Ð.
    Let's assume that I'm extending a graphical file chooser class (JFileChooser). This class has methods which display the file chooser dialog and return a status signature in the form of an int: APPROVE_OPTION if the user selects a file and hits Open /Save, CANCEL_OPTION if the user hits Cancel, and ERROR_OPTION if something goes wrong. These methods are called showDialog(). I find this cumbersome, so I decide to make another method that returns a File object: in the case of APPROVE_OPTION, it returns the file selected by the user; otherwise, it returns null. This is where I run into a problem: would it be okay for me to keep the showDialog() name, even though methods with that name — and a different return type — already exist? To top it off, my method takes an additional parameter: a File which denotes in which directory the file chooser should start. My question to you: Is it okay to call a method the same name as a superclass method if they return different types? Or would that be confusing to API users? (If so, what other name could I use?) Alternatively, should I keep the name and change the return type so it matches that of the other methods? public int showDialog(Component parent, String approveButtonText) // Superclass method public File showDialog(Component parent, File location) // My method

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  • Magento - How to manage multiple base currencies and multiple payment gateways?

    - by Diego
    I have two requirements to satisfy, I hope someone with more experience can help me sorting them out. Multiple Base Currencies My client wants to allow visitors to place orders in whatever currency they prefer, choosing from the ones he’ll configure. Magento only supports one Base Currency, and this is, obviously, not what I need. I checked the solution involving multiple websites, but I need a customer to be registered once and stay on the same website, not to switch from one to the other and have to register/log in on each. Manage multiple Payment Gateways per currency and per payment method This is another crucial requirement, and it’s tied to the first one. My client wants to “route” payments in different currencies to different accounts. He’ll thus have one for Euro, one for USD and one for GBP. Whenever a customer pays with one of these currencies, the payment gateway has to be chosen accordingly. Additionally, the gateway should be different depending on other rules. For example, if customer pays with a Debit Card, my client will have a payment gateway configured especially for it. If customer pays with MasterCard, the gateway will be different, and so on. The complication, in this case, arises from the fact that my client uses Realex Payments and, although it would be possible for him to open multiple accounts, the Realex module expects one single gateway. In a normal scenario, we would need up to six instead: Payment with Debit Card in Euro Payment with Credit Card in Euro Payment with Debit Card in US Dollars Payment with Credit Card in US Dollars Payment with Debit Card in GB Pounds Payment with Credit Card in GB Pounds This, of course, if he doesn’t decide to accept other payment methods, such as bank transfer, which would add one more gateway per currency. Is there a way to achieve the above in Magento? I never had such complicated requirements before, and I’m a bit lost. Thanks in advance for the help.

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  • Why does Java allow to implement different interfaces, each containing a method with the same signature?

    - by Software Engeneering Learner
    I've recently found that I can have two interfaces containing method with the same signature as a method in the other interface. And then I can have an interface or class that implements both of that interfaces. So the descendant class/interface has implicitly implements two different methods as a one method. Why is this allowed in Java? I can see a numerous problems that arises from that. Even eclipse only can find out about implementations for only one interface method, but for the second one it doesn't show any implementations at all. Also I believe there would be problems with automatic refactoring, like when you would like to change the signature of the method in one of the interfaces and IDE won't be able to correctly change that signature in all implementations, as they implement two different interfaces and how will IDE know what interface method it implementation descends. Why don't just make a compiler error like 'interfaces method names clashes' or something like that?

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  • Matching the superclass's constructor's parameter list, is treating a null default value as a non-null value within a constructor a violation of LSP?

    - by Panzercrisis
    I kind of ran into this when messing around with FlashPunk, and I'm going to use it as an example. Essentially the main sprite class is pretty much class Entity. Entity's constructor has four parameters, each with a default value. One of them is graphic, whose default value is null. Entity is designed to be inherited from, with many such subclasses providing their own graphic within their own internal workings. Normally these subclasses would not have graphic in their constructor's parameter lists, but would simply pick something internally and go with it. However I was looking into possibly still adhering to the Liskov Substitution Principal. Which led me to the following example: package com.blank.graphics { import net.flashpunk.*; import net.flashpunk.graphics.Image; public class SpaceGraphic extends Entity { [Embed(source = "../../../../../../assets/spaces/blank.png")] private const BLANK_SPACE:Class; public function SpaceGraphic(x:Number = 0, y:Number = 0, graphic:Graphic = null, mask:Mask = null) { super(x, y, graphic, mask); if (!graphic) { this.graphic = new Image(BLANK_SPACE); } } } } Alright, so now there's a parameter list in the constructor that perfectly matches the one in the super class's constructor. But if the default value for graphic is used, it'll exhibit two different behaviors, depending on whether you're using the subclass or the superclass. In the superclass, there won't be a graphic, but in the subclass, it'll choose the default graphic. Is this a violation of the Liskov Substitution Principal? Does the fact that subclasses are almost intended to use different parameter lists have any bearing on this? Would minimizing the parameter list violate it in a case like this? Thanks.

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  • Very simple OOP question

    - by Mosty Mostacho
    I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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  • Multiple sites with the same codebase in Python

    - by Jimmy
    I am trying to run a large amount of sites which share about 90% of their code. They are simply designed to query an API and return the results. They will have a common userbase / database but will be configured slightly different and will have different CSS (perhaps even different templating). My initial idea was to run them as separate applications with a common library but I have read about the sites framework which would allow them to run from a single instance of Django which may help to reduce memory usage. https://docs.djangoproject.com/en/dev/ref/contrib/sites/ Is the site framework the right approach to a problem like this, and does it have real benefits over running separate applications? Initially I thought it was, but now I think otherwise. I have heard the following: Your SITE_ID is set in settings.py, so in order to have multiple sites, you need multiple settings.py configurations, which means multiple distinct processes/instances. You can of course share the code base between them, but each site will need a dedicated worker / WSGIDaemon to serve the site. This effectively removes any benefit of running multiple sites under one hood, if each site needs a UWSGI instance running. Alternative ideas of systems: https://github.com/iivvoo/django_layers https://github.com/shestera/django-multisite I don't know what route to be taking with this.

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  • Implementation of instance testing in Java, C++, C#

    - by Jake
    For curiosity purposes as well as understanding what they entail in a program, I'm curious as to how instance testing (instanceof/is/using dynamic_cast in c++) works. I've tried to google it (particularly for java) but the only pages that come up are tutorials on how to use the operator. How do the implementations vary across those langauges? How do they treat classes with identical signatures? Also, it's been drilled into my head that using instance testing is a mark of bad design. Why exactly is this? When is that applicable, instanceof should still be used in methods like .equals() and such right? I was also thinking of this in the context of exception handling, again particularly in Java. When you have mutliple catch statements, how does that work? Is that instance testing or is it just resolved during compilation where each thrown exception would go to?

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  • How do you handle objects that need custom behavior, and need to exist as an entity in the database?

    - by Scott Whitlock
    For a simple example, assume your application sends out notifications to users when various events happen. So in the database I might have the following tables: TABLE Event EventId uniqueidentifier EventName varchar TABLE User UserId uniqueidentifier Name varchar TABLE EventSubscription EventUserId EventId UserId The events themselves are generated by the program. So there are hard-coded points in the application where an event instance is generated, and it needs to notify all the subscribed users. So, the application itself doesn't edit the Event table, except during initial installation, and during an update where a new Event might be created. At some point, when an event is generated, the application needs to lookup the Event and get a list of Users. What's the best way to link the event in the source code to the event in the database? Option 1: Store the EventName in the program as a fixed constant, and look it up by name. Option 2: Store the EventId in the program as a static Guid, and look it up by ID. Extra Credit In other similar circumstances I may want to include custom behavior with the event type. That is, I'll want subclasses of my Event entity class with different behaviors, and when I lookup an event, I want it to return an instance of my subclass. For instance: class Event { public Guid Id { get; } public Guid EventName { get; } public ReadOnlyCollection<EventSubscription> EventSubscriptions { get; } public void NotifySubscribers() { foreach(var eventSubscription in EventSubscriptions) { eventSubscription.Notify(); } this.OnSubscribersNotified(); } public virtual void OnSubscribersNotified() {} } class WakingEvent : Event { private readonly IWaker waker; public WakingEvent(IWaker waker) { if(waker == null) throw new ArgumentNullException("waker"); this.waker = waker; } public override void OnSubscribersNotified() { this.waker.Wake(); base.OnSubscribersNotified(); } } So, that means I need to map WakingEvent to whatever key I'm using to look it up in the database. Let's say that's the EventId. Where do I store this relationship? Does it go in the event repository class? Should the WakingEvent know declare its own ID in a static member or method? ...and then, is this all backwards? If all events have a subclass, then instead of retrieving events by ID, should I be asking my repository for the WakingEvent like this: public T GetEvent<T>() where T : Event { ... // what goes here? ... } I can't be the first one to tackle this. What's the best practice?

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  • What alternative is better to diagram this scenario?

    - by Mosty Mostacho
    I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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  • Avoid overwriting all the methods in the child class

    - by Heckel
    The context I am making a game in C++ using SFML. I have a class that controls what is displayed on the screen (manager on the image below). It has a list of all the things to draw like images, text, etc. To be able to store them in one list I created a Drawable class from which all the other drawable class inherit. The image below represents how I would organize each class. Drawable has a virtual method Draw that will be called by the manager. Image and Text overwrite this method. My problem is that I would like Image::draw method to work for Circle, Polygon, etc. since sf::CircleShape and sf::ConvexShape inherit from sf::Shape. I thought of two ways to do that. My first idea would be for Image to have a pointer on sf::Shape, and the subclasses would make it point onto their sf::CircleShape or sf::ConvexShape classes (Like on the image below). In the Polygon constructor I would write something like ptr_shape = &polygon_shape; This doesn't look very elegant because I have two variables that are, in fact, just one. My second idea is to store the sf::CircleShape and sf::ConvexShape inside the ptr_shape like ptr_shape = new sf::ConvexShape(...); and to use a function that is only in ConvexShape I would cast it like so ((sf::ConvexShape*)ptr_shape)->convex_method(); But that doesn't look very elegant either. I am not even sure I am allowed to do that. My question I added details about the whole thing because I thought that maybe my whole architecture was wrong. I would like to know how I could design my program to be safe without overwriting all the Image methods. I apologize if this question has already been asked; I have no idea what to google.

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  • Are trivial protected getters blatant overkill?

    - by Panzercrisis
    Something I really have not thought about before (AS3 syntax): private var m_obj:Object; protected function get obj():Object { return m_obj; } private var m_str:String; protected function get str():String { return m_str; } At least subclasses won't be able to set m_obj or m_str (though they could still modify m_obj). Is this just blatant overkill? I am not talking about doing this as opposed to making them public. I am talking about doing this instead of just making the variables themselves protected. Like this: protected var m_obj:Object; //more accessible than a private variable with a protected getter protected var m_str:String; //more accessible than a private variable with a protected getter

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  • OO Software Architecture - base class that everything inherits from. Bad/good idea?

    - by ale
    I am reviewing a proposed OO software architecture that looks like this: Base Foo Something Bar SomethingElse Where Base is a static class. My immediate thought was that every object in any class will inherit all the methods in Base which would create a large object. Could this cause problems for a large system? The whole architecture is hierarchical.. the 'tree' is much bigger than this really. Does this sort of architecture have a name (hierarchical?!). What are the known pros and cons?

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  • REST API wrapper - class design for 'lite' object responses

    - by sasfrog
    I am writing a class library to serve as a managed .NET wrapper over a REST API. I'm very new to OOP, and this task is an ideal opportunity for me to learn some OOP concepts in a real-life situation that makes sense to me. Some of the key resources/objects that the API returns are returned with different levels of detail depending on whether the request is for a single instance, a list, or part of a "search all resources" response. This is obviously a good design for the REST API itself, so that full objects aren't returned (thus increasing the size of the response and therefore the time taken to respond) unless they're needed. So, to be clear: .../car/1234.json returns the full Car object for 1234, all its properties like colour, make, model, year, engine_size, etc. Let's call this full. .../cars.json returns a list of Car objects, but only with a subset of the properties returned by .../car/1234.json. Let's call this lite. ...search.json returns, among other things, a list of car objects, but with minimal properties (only ID, make and model). Let's call this lite-lite. I want to know what the pros and cons of each of the following possible designs are, and whether there is a better design that I haven't covered: Create a Car class that models the lite-lite properties, and then have each of the more detailed responses inherit and extend this class. Create separate CarFull, CarLite and CarLiteLite classes corresponding to each of the responses. Create a single Car class that contains (nullable?) properties for the full response, and create constructors for each of the responses which populate it to the extent possible (and maybe include a property that returns the response type from which the instance was created). I expect among other things there will be use cases for consumers of the wrapper where they will want to iterate through lists of Cars, regardless of which response type they were created from, such that the three response types can contribute to the same list. Happy to be pointed to good resources on this sort of thing, and/or even told the name of the concept I'm describing so I can better target my research.

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  • Is "If a method is re-used without changes, put the method in a base class, else create an interface" a good rule-of-thumb?

    - by exizt
    A colleague of mine came up with a rule-of-thumb for choosing between creating a base class or an interface. He says: Imagine every new method that you are about to implement. For each of them, consider this: will this method be implemented by more than one class in exactly this form, without any change? If the answer is "yes", create a base class. In every other situation, create an interface. For example: Consider the classes cat and dog, which extend the class mammal and have a single method pet(). We then add the class alligator, which doesn't extend anything and has a single method slither(). Now, we want to add an eat() method to all of them. If the implementation of eat() method will be exactly the same for cat, dog and alligator, we should create a base class (let's say, animal), which implements this method. However, if it's implementation in alligator differs in the slightest way, we should create an IEat interface and make mammal and alligator implement it. He insists that this method covers all cases, but it seems like over-simplification to me. Is it worth following this rule-of-thumb?

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  • SQL Server Table Polling by Multiple Subscribers

    - by Daniel Hester
    Background Designing Stored Procedures that are safe for multiple subscribers (to call simultaneously) can be challenging.  For example let’s say that you want multiple worker processes to poll a shared work queue that’s encapsulated as a SQL Table. This is a common scenario and through experience you’ll find that you want to use Table Hints to prevent unwanted locking when performing simultaneous queries on the same table. There are three table hints to consider: NOLOCK, READPAST and UPDLOCK. Both NOLOCK and READPAST table hints allow you to SELECT from a table without placing a LOCK on that table. However, SELECTs with the READPAST hint will ignore any records that are locked due to being updated/inserted (or otherwise “dirty”), whereas a SELECT with NOLOCK ignores all locks including dirty reads. For the initial update of the flag (that marks the record as available for subscription) I don’t use the NOLOCK Table Hint because I want to be sensitive to the “active” records in the table and I want to exclude them.  I use an Update Lock (UPDLOCK) in conjunction with a WHERE clause that uses a sub-select with a READPAST Table Hint in order to explicitly lock the records I’m updating (UPDLOCK) but not place a lock on the table when selecting the records that I’m going to update (READPAST). UPDATES should be allowed to lock the rows affected because we’re probably changing a flag on a record so that it is not included in a SELECT from another subscriber. On the UPDATE statement we should explicitly use the UPDLOCK to guard against lock escalation. A SELECT to check for the next record(s) to process can result in a shared read lock being held by more than one subscriber polling the shared work queue (SQL table). It is expected that more than one worker process (or server) might try to process the same new record(s) at the same time. When each process then tries to obtain the update lock, none of them can because another process has a shared read lock in place. Thus without the UPDLOCK hint the result would be a lock escalation deadlock; however with the UPDLOCK hint this condition is mitigated against. Note that using the READPAST table hint requires that you also set the ISOLATION LEVEL of the transaction to be READ COMMITTED (rather than the default of SERIALIZABLE). Guidance In the Stored Procedure that returns records to the multiple subscribers: Perform the UPDATE first. Change the flag that makes the record available to subscribers.  Additionally, you may want to update a LastUpdated datetime field in order to be able to check for records that “got stuck” in an intermediate state or for other auditing purposes. In the UPDATE statement use the (UPDLOCK) Table Hint on the UPDATE statement to prevent lock escalation. In the UPDATE statement also use a WHERE Clause that uses a sub-select with a (READPAST) Table Hint to select the records that you’re going to update. In the UPDATE statement use the OUTPUT clause in conjunction with a Temporary Table to isolate the record(s) that you’ve just updated and intend to return to the subscriber. This is the fastest way to update the record(s) and to get the records’ identifiers within the same operation. Finally do a set-based SELECT on the main Table (using the Temporary Table to identify the records in the set) with either a READPAST or NOLOCK table hint.  Use NOLOCK if there are other processes (besides the multiple subscribers) that might be changing the data that you want to return to the multiple subscribers; or use READPAST if you're sure there are no other processes (besides the multiple subscribers) that might be updating column data in the table for other purposes (e.g. changes to a person’s last name).  NOLOCK is generally the better fit in this part of the scenario. See the following as an example: CREATE PROCEDURE [dbo].[usp_NewCustomersSelect] AS BEGIN -- OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON -- DECLARE TEMP TABLE -- Note that this example uses CustomerId as an identifier; -- you could just use the Identity column Id if that’s all you need. DECLARE @CustomersTempTable TABLE ( CustomerId NVARCHAR(255) ) -- PERFORM UPDATE FIRST -- [Customers] is the name of the table -- [Id] is the Identity Column on the table -- [CustomerId] is the business document key used to identify the -- record globally, i.e. in other systems or across SQL tables -- [Status] is INT or BIT field (if the status is a binary state) -- [LastUpdated] is a datetime field used to record the time of the -- last update UPDATE [Customers] WITH (UPDLOCK) SET [Status] = 1, [LastUpdated] = GETDATE() OUTPUT [INSERTED].[CustomerId] INTO @CustomersTempTable WHERE ([Id] = (SELECT TOP 100 [Id] FROM [Customers] WITH (READPAST) WHERE ([Status] = 0) ORDER BY [Id] ASC)) -- PERFORM SELECT FROM ENTITY TABLE SELECT [C].[CustomerId], [C].[FirstName], [C].[LastName], [C].[Address1], [C].[Address2], [C].[City], [C].[State], [C].[Zip], [C].[ShippingMethod], [C].[Id] FROM [Customers] AS [C] WITH (NOLOCK), @CustomersTempTable AS [TEMP] WHERE ([C].[CustomerId] = [TEMP].[CustomerId]) END In a system that has been designed to have multiple status values for records that need to be processed in the Work Queue it is necessary to have a “Watch Dog” process by which “stale” records in intermediate states (such as “In Progress”) are detected, i.e. a [Status] of 0 = New or Unprocessed; a [Status] of 1 = In Progress; a [Status] of 2 = Processed; etc.. Thus, if you have a business rule that states that the application should only process new records if all of the old records have been processed successfully (or marked as an error), then it will be necessary to build a monitoring process to detect stalled or stale records in the Work Queue, hence the use of the LastUpdated column in the example above. The Status field along with the LastUpdated field can be used as the criteria to detect stalled / stale records. It is possible to put this watchdog logic into the stored procedure above, but I would recommend making it a separate monitoring function. In writing the stored procedure that checks for stale records I would recommend using the same kind of lock semantics as suggested above. The example below looks for records that have been in the “In Progress” state ([Status] = 1) for greater than 60 seconds: CREATE PROCEDURE [dbo].[usp_NewCustomersWatchDog] AS BEGIN -- TO OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON DECLARE @MaxWait int; SET @MaxWait = 60 IF EXISTS (SELECT 1 FROM [dbo].[Customers] WITH (READPAST) WHERE ([Status] = 1) AND (DATEDIFF(s, [LastUpdated], GETDATE()) > @MaxWait)) BEGIN SELECT 1 AS [IsWatchDogError] END ELSE BEGIN SELECT 0 AS [IsWatchDogError] END END Downloads The zip file below contains two SQL scripts: one to create a sample database with the above stored procedures and one to populate the sample database with 10,000 sample records.  I am very grateful to Red-Gate software for their excellent SQL Data Generator tool which enabled me to create these sample records in no time at all. References http://msdn.microsoft.com/en-us/library/ms187373.aspx http://www.techrepublic.com/article/using-nolock-and-readpast-table-hints-in-sql-server/6185492 http://geekswithblogs.net/gwiele/archive/2004/11/25/15974.aspx http://grounding.co.za/blogs/romiko/archive/2009/03/09/biztalk-sql-receive-location-deadlocks-dirty-reads-and-isolation-levels.aspx

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  • Multi-core processors: Better performance running multiple applications?

    - by aip.cd.aish
    I realize for single applications - the application itself has to be designed to take advantage of multiple cores. But what about executing many different applications simultaneously? On my development machine at an average instance, I run multiple servers (a database server, a web server), multiple instance of IDEs (either Visual Studio or NetBeans), Web-browser with multiple tabs (in Chrome, each tab is a process on its own), FTP client, SSH client etc. Does having a multi-core system improve the ability to run multiple applications simultaneously?

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  • Puppet class inheritance confusion

    - by EMiller
    I've read the documentation on scope, but I'm still having trouble working this out. I've got two environments that are very similar - so I've got: modules/django-env/manifests/init.pp class django-env { package { "python26": ensure => installed } # etc ... } import "er.pp" modules/django-env/manifests/er.pp $venvname = "er" $venvpath = "/home/django/virtualenvs" class er { file { "$venvpath/$venvname" : ensure => directory } # etc ... } class er-dev { include er } class er-bce-dev { $venvname = "er-bce" include er } manifests/modules.pp import "django-env" manifests/nodes.pp node default { # etc ... } node 'centos-dev' imports default { include django-env include er-bce-dev include er-dev } The result here is that the "inheritance" works - but only the first "er-" item under the 'centos-dev' node is acted upon, I either get er-bce-dev or er-dev, but not both. There must be some basic thing I'm misunderstanding here. Is it the difference between import and include ? (not sure I understand that)

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  • converting node inheritance to hiera

    - by quickshiftin
    I'm working on moving over a node inheritance tree to hiera. Presently working on the hierarchy. Prior to hiera, my nodes had a hierarchy as such base pre-prod qa nodes staging nodes development nodes prod nodes Now I'm trying to get the same tier with hiera. Starting out I have this :hierarchy: - base - "%{environment}" - "%{clientcert}" but I need another level to capture pre-prod and prod. My thought would be to add an entry to puppet.conf, something like [agent] realm = pre-prod then :hierarchy: - base - "%{realm}" - "%{environment}" - "%{clientcert}" A couple of questions Are you allowed to place arbitrary properties into puppet.conf? Will hiera see the realm property?

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  • Boost.Python wrapping hierarchies avoiding diamond inheritance

    - by stbuton
    I'm having some trouble seeing what the best way to wrap a series of classes with Boost.Python while avoiding messy inheritance problems. Say I have the classes A, B, and C with the following structure: struct A { virtual void foo(); virtual void bar(); virtual void baz(); }; struct B : public A { virtual void quux(); }; struct C : public A { virtual void foobar(); }; I want to wrap all classes A, B, and C such that they are extendable from Python. The normal method for accomplishing this would be along the lines of: struct A_Wrapper : public A, boost::python::wrapper<A> { //dispatch logic for virtual functions }; Now for classes B and C which extend from A I would like to be able to inherit and share the wrapping implementation for A. So I'd like to be able to do something along the lines of: struct B_Wrapper : public B, public A_Wrapper, public boost::python::wrapper<B> { //dispatch logic specific for B }; struct C_Wrapper : public C, public A_Wrapper, public boost::python::wrapper<C> { //dispatch logic specific for C } However, it seems like that would introduce all manner of nastiness with the double inheritance of the boost wrapper base and the double inheritance of A in the B_Wrapper and C_Wrapper objects. Is there a common way that this instance is solved that I'm missing? thanks.

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  • Inheritance concept in jpa

    - by megala
    I created one table using Inheritance concept to sore data into google app engine datastore. It contained following coding but it shows error.How to user Inheritance concept.What error in my program Program 1: @Entity @Inheritance(strategy=InheritanceType.JOINED) public class calender { @Id private String EmailId; @Basic private String CalName; @Basic public void setEmailId(String emailId) { EmailId = emailId; } public String getEmailId() { return EmailId; } public void setCalName(String calName) { CalName = calName; } public String getCalName() { return CalName; } public calender(String EmailId,String CalName) { this.EmailId=EmailId; this.CalName=CalName; } } program 2: @Entity public class method { @Id private String method; public void setMethod(String method) { this.method = method; } public String getMethod() { return method; } public method(String method) { this.method=method; } } My constraint is I want ouput like this Calendertable coantain Emailid calenername and method table contain Emailid method How to achive this? thanks inadvance.

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  • Geometry shader for multiple primitives

    - by Byte56
    How can I create a geometry shader that can handle multiple primitives? For example when creating a geometry shader for triangles, I define a layout like so: layout(triangles) in; layout(triangle_strip, max_vertices=3) out; But if I use this shader then lines or points won't show up. So adding: layout(triangles) in; layout(triangle_strip, max_vertices=3) out; layout(lines) in; layout(line_strip, max_vertices=2) out; The shader will compile and run, but will only render lines (or whatever the last primitive defined is). So how do I define a single geometry shader that will handle multiple types of primitives? Or is that not possible and I need to create multiple shader programs and change shader programs before drawing each type?

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  • Generate Multiple Choice Questions [closed]

    - by Daniel
    I'm working on a quiz application that will have a number of multiple choice questions. I'm waiting on the content from the client, but I'm hoping to start testing with some placeholder data for the time being. In order for the tests to be worthwhile, I probably need at least 100 multiple choice questions. I wanted to see if anyone knows of a resource or tool that can generate questions/multiple choice answers or propose another creative way to fill my quiz application with placeholder content. Ultimately the data will be in a MySQL database, but I don't really care what format the sample data is in (Excel, Word, JSON, etc.).

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  • Google Analytics with multiple environments

    - by marcof
    We are planning to use Google Analytics in our organization and I am in charge for setting it up. I was wondering how to deal with multiple environments. We sure do not want to collect data during development and QA (or maybe collect data to a different analytics account), but we want to when the site goes to production (obviously). How do you deal with multiple environments and Google Analytics ? Do you setup multiple accounts for Google Analytics and use either one depending on the environement ? We're using ASP.NET 2.0, if that matters.

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  • AngularJS: structuring a web application with multiple ng-apps

    - by mg1075
    The blogosphere has a number of articles on the topic of AngularJS app structuring guidelines such as these (and others): http://www.johnpapa.net/angular-app-structuring-guidelines/ http://codingsmackdown.tv/blog/2013/04/19/angularjs-modules-for-great-justice/ http://danorlando.com/angularjs-architecture-understanding-modules/ http://henriquat.re/modularizing-angularjs/modularizing-angular-applications/modularizing-angular-applications.html However, one scenario I have yet to come across for guidelines and best practices is the case where you have a large web application containing multiple "mini-spa" apps, and the mini-spa apps all share a certain amount of code. I am not referring to the case of trying to have multiple ng-app declarations on the same page; rather, I mean different sections of a large site that have their own, unique ng-app declaration. As Scott Allen writes in his OdeToCode blog: One scenario I haven't found addressed very well is the scenario where multiple apps exist in the same greater web application and require some shared code on the client. Are there any recommended approaches to take, pitfalls to avoid, or good sample structures of this scenario that you can point to?

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