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  • Gathering IP address and workstation information; does it belong in a state class?

    - by p.campbell
    I'm writing an enterprisey utility that collects exception information and writes to the Windows Event Log, sends an email, etc. This utility class will be used by all applications in the corporation: web, BizTalk, Windows Services, etc. Currently this class: holds state given to it via public properties calls out to .NET Framework methods to gather information about runtime details. Included are call to various properties and methods from System.Environment, Reflection details, etc. This implementation has the benefit of allowing all those callers not to have to make these same calls themselves. This means less code for the caller to forget, screw up, etc. Should this state class (please what's the phrase I'm looking for [like DTO]?) know how to resolve/determine runtime details (like the IP address and machine name that it's running on)? It seems to me on second thought that it's meant to be a class that should hold state, and not know how to call out to the .NET Framework to find information. var myEx = new AppProblem{MachineName="Riker"}; //Will get "Riker 10.0.0.1" from property MachineLongDesc Console.WriteLine("full machine details: " + myEx.MachineLongDesc); public class AppProblem { public string MachineName{get;set;} public string MachineLongDesc{ get{ if(string.IsNullOrEmpty(this.MachineName) { this.MachineName = Environment.MachineName; } return this.MachineName + " " + GetCurrentIP(); } } private string GetCurrentIP() { return System.Net.Dns.GetHostEntry(this.MachineName) .AddressList.First().ToString(); } } This code was written by hand from memory, and presented for simplicity, trying to illustrate the concept.

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  • How to make the members of my Data Access Layer object aware of their siblings

    - by Graham
    My team currently has a project with a data access object composed like so: public abstract class DataProvider { public CustomerRepository CustomerRepo { get; private set; } public InvoiceRepository InvoiceRepo { get; private set; } public InventoryRepository InventoryRepo { get; private set; } // couple more like the above } We have non-abstract classes that inherit from DataProvider, and the type of "CustomerRepo" that gets instantiated is controlled by that child class. public class FloridaDataProvider { public FloridaDataProvider() { CustomerRepo = new FloridaCustomerRepo(); // derived from base CustomerRepository InvoiceRepo = new InvoiceRespository(); InventoryRepo = new InventoryRepository(); } } Our problem is that some of the methods inside a given repo really would benefit from having access to the other repo's. Like, a method inside InventoryRepository needs to get to Customer data to do some determinations, so I need to pass in a reference to a CustomerRepository object. Whats the best way for these "sibling" repos to be aware of each other and have the ability to call each other's methods as-needed? Virtually all the other repos would benefit from having the CustomerRepo, for example, because it is where names/phones/etc are selected from, and these data elements need to be added to the various objects that are returned out of the other repos. I can't just new-up a plain "CustomerRepository" object inside a method within a different repo, because it might not be the base CustomerRepository that actually needs to run.

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  • XNA - Obtaining depth from the scene's render target?

    - by user1423893
    I'm currently rendering my scene to a render target so it can be used for rendering methods such as post processing and order independent transparency. rtScene = new RenderTarget2D( GraphicsDevice, GraphicsDevice.PresentationParameters.BackBufferWidth, GraphicsDevice.PresentationParameters.BackBufferHeight, false, SurfaceFormat.Rgba64, DepthFormat.Depth24Stencil8, // Requires a depth format for objects to be drawn correctly (e.g. wireframe model surrounding model) 0, RenderTargetUsage.PreserveContents ); I am required to use RenderTargetUsage.PreserveContents so that the same render target can be rendered to multiple times, once for each of the draw methods below. DrawBackground DrawDeferred DrawForward DrawTransparent The problem is that DrawTransparent requires a copy of the scene's depth as a texture. Is there any way to obtain this from the scene render target above (rtScene)? I can't have more than one render target with RenderTargetUsage.PreserveContents as this causes problems on hardware such as the XBOX 360, so rendering the depth to a separate render target at the same time as I render the scene isn't possible as far as I can tell. Would I be able to get around this problem by "Ping-Ponging" two render targets (using the more compatible RenderTargetUsage.DiscardContents) and using the result for the depth texture?

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  • AI agents with FSM: a question regarding this

    - by Prog
    Finite State Machines implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. However I have a question regarding how this is used in games to design AI agents. Please consider a class Monster that represents an AI agent. Simplified it looks like this: class Monster{ State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses that implement execute() differently. So far classic State pattern. Here's my question: AI agents are subject to environmental effects and other objects communicating with them. For example an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. My question is divided to two parts: 1- Please say if this is correct: With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Correct? Or wrong? 2- If correct, than how is this done? Are all states obligated by their superclass) to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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  • Dependency Injection and method signatures

    - by sunwukung
    I've been using YADIF (yet another dependency injection framework) in a PHP/Zend app I'm working on to handle dependencies. This has achieved some notable benefits in terms of testing and decoupling classes. However,one thing that strikes me is that despite the sleight of hand performed when using this technique, the method names impart a degree of coupling. Probably not the best example -but these methods are distinct from ... say the PEAR Mailer. The method names themselves are a (subtle) form of coupling //example public function __construct($dic){ $this->dic = $dic; } public function example(){ //this line in itself indicates the YADIF origin of the DIC $Mail= $dic->getComponent('mail'); $Mail->setBodyText($body); $Mail->setFrom($from); $Mail->setSubject($subject); } I could write a series of proxies/wrappers to hide these methods and thus promote decoupling from , but this seems a bit excessive. You have to balance purity with pragmatism... How far would you go to hide the dependencies in your classes?

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  • FP for simulation and modelling

    - by heaptobesquare
    I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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  • Command Query Separation

    - by Liam McLennan
    Command query separation is a strategy, proposed by Bertrand Meyer, that each of an object’s methods should be either a command or a query. A command is an operation that changes the state of a system, and a query is an operation that returns a value. This is not the same thing as CQRS, hence why I think that CQRS is poorly named. An Example of Command Query Separation Consider a system that models books and shelves. There is a rule that a shelf may not be removed if it holds any books. One way to implement the removal is to write a method Shelf.Remove() that internally checks to make sure that the shelf is empty before removing it. If the shelf is not empty then it is not removed and an error is returned. To implement this feature following the principle of command query separation would require two methods, one to query the shelf and determine if it is empty and a second method to remove the shelf. Separating the query from the command makes the shelf class simpler to use because the state change is clear and explicit.

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  • Understanding interfaces [closed]

    - by user985482
    Possible Duplicate: When to use abstract classes instead of interfaces and extension methods in C#? Why are interfaces useful? What is the point of an interface? What other reasons are there to write interfaces rather than abstract classes? What is the point of having every service class have an interface? Is it bad habit not using interfaces? I am reading Microsoft Visual C# 2010 Step by Step which I feel it is a very good book on introducing you to the C# language. I have just finished reading a chapter on interfaces and although I understood the syntax of creating and using interfaces I have trouble of understanding the point on why should I use them? Correct me If I am wrong but in an interface you can only declare methods names and parameters.The body of the method should be declared in the class that inherits the interface. So in this case why should I declare an interface if I am going to declare the entire method in the class that inherits that interface? What is the point? Does this have something to do with the fact that a class can inherit multiple interfaces?

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  • Is the Entity Component System architecture object oriented by definition?

    - by tieTYT
    Is the Entity Component System architecture object oriented, by definition? It seems more procedural or functional to me. My opinion is that it doesn't prevent you from implementing it in an OO language, but it would not be idiomatic to do so in a staunchly OO way. It seems like ECS separates data (E & C) from behavior (S). As evidence: The idea is to have no game methods embedded in the entity. And: The component consists of a minimal set of data needed for a specific purpose Systems are single purpose functions that take a set of entities which have a specific component I think this is not object oriented because a big part of being object oriented is combining your data and behavior together. As evidence: In contrast, the object-oriented approach encourages the programmer to place data where it is not directly accessible by the rest of the program. Instead, the data is accessed by calling specially written functions, commonly called methods, which are bundled in with the data. ECS, on the other hand, seems to be all about separating your data from your behavior.

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  • Must all AI states be able to react to any event?

    - by Prog
    FSMs implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. How is this used in games to design AI agents? Consider a simplified class Monster, representing an AI agent: class Monster { State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses implementing execute() differently. So far, classic State pattern. AI agents are subject to environmental effects and other objects communicating with them. For example, an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Is this correct? If correct, how is this done? Are all states obligated by their superclass to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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  • Generating random tunnels

    - by IVlad
    What methods could we use to generate a random tunnel, similar to the one in this classic helicopter game? Other than that it should be smooth and allow you to navigate through it, while looking as natural as possible (not too symmetric but not overly distorted either), it should also: Most importantly - be infinite and allow me to control its thickness in time - make it narrower or wider as I see fit, when I see fit; Ideally, it should be possible to efficiently generate it with smooth curves, not rectangles as in the above game; I should be able to know in advance what its bounds are, so I can detect collisions and generate powerups inside the tunnel; Any other properties that let you have more control over it or offer optimization possibilities are welcome. Note: I'm not asking for which is best or what that game uses, which could spark extended discussion and would be subjective, I'm just asking for some methods that others know about or have used before or even think they might work. That is all, I can take it from there. Also asked on stackoverflow, where someone suggested I should ask here too. I think it fits in both places, since it's as much an algorithm question as it is a gamedev question, IMO.

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  • How can I reduce the amount of time it takes to fully regression test an application ready for release?

    - by DrLazer
    An app I work on is being developed with a modified version of scrum. If you are not familiar with scrum, it's just an alternative approach to a more traditional watefall model, where a series of features are worked on for a set amount of time known as a sprint. The app is written in C# and makes use of WPF. We use Visual C# 2010 Express edition as an IDE. If we work on a sprint and add in a few new features, but do not plan to release until a further sprint is complete, then regression testing is not an issue as such. We just test the new features and give the app a good once over. However, if a release is planned that our customers can download - a full regression test is factored in. In the past this wasn't a big deal, it took 3 or 4 days and the devs simply fix up any bugs found in the regression phase, but now, as the app is getting larger and larger and incorporating more and more features, the regression is spanning out for weeks. I am interested in any methods that people know of or use that can decrease this time. At the moment the only ideas I have are to either start writing Unit Tests, which I have never fully tried out in a commercial environment, or to research the possibilty of any UI Automation API's or tools that would allow me to write a program to perform a series of batch tests. I know literally nothing about the possibilities of UI automation so any information would be valuable. I don't know that much about Unit testing either, how complicated can the tests be? Is it possible to get Unit tests to use the UI? Are there any other methods I should consider? Thanks for reading, and for any advice in advance.

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  • How to choose between using a Domain Event, or letting the application layer orchestrate everything

    - by Mr Happy
    I'm setting my first steps into domain driven design, bought the blue book and all, and I find myself seeing three ways to implement a certain solution. For the record: I'm not using CQRS or Event Sourcing. Let's say a user request comes into the application service layer. The business logic for that request is (for whatever reason) separated into a method on an entity, and a method on a domain service. How should I go about calling those methods? The options I have gathered so far are: Let the application service call both methods Use method injection/double dispatch to inject the domain service into the entity, letting the entity do it's thing and then let it call the method of the domain service (or the other way around, letting the domain service call the method on the entity) Raise a domain event in the entity method, a handler of which calls the domain service. (The kind of domain events I'm talking about are: http://www.udidahan.com/2009/06/14/domain-events-salvation/) I think these are all viable, but I'm unable to choose between them. I've been thinking about this a long time and I've come to a point where I no longer see the semantic differences between the three. Do you know of some guidelines when to use what?

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  • Motivation for service layer (instead of just copying dlls)?

    - by BornToCode
    I'm creating an application which has 2 different UIs so I'm making it with a service layer which I understood is appropriate for such case. However I found myself just creating web methods for every single method I have in the BL layer, so the services basically built from methods that looks like this: return customers_bl.Get_Customer_Prices(customer_id); I understood that a main point of the service layer is to prevent duplication of code so I asked myself - well, why not just import the BL.dll (and the DAL.dll) to the other UI, and whenever making a change re-copy the dll files, it might not be so 'neat', but is the all purpose of the service layer to prevent this? {I know something is wrong in my approach, I'm probably missing the importance of service layer, I'd like to get more motivation to create another layer, especially because as it is I found that many of my BL functions ALREADY looks like: return customers_dal.Get_Customer_Prices(cust_id) which led me to ask: was it really necessary to create the BL just because on several functions I actually have LOGIC inside the BL?} so I'm looking for more motivation to creating ONE MORE layer, I'm sure it's not just to make it more convenient that I won't have to re-copy the dlls on changes? Am I grasping it wrong? Any simple guidelines on how to design service layer (corresponding to all the BL layer functions or not? any simple example?) any enlightenment on the subject?

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  • Should this code/logic be included in Business Objects class or a separate class?

    - by aspdotnetuser
    I have created a small application which has a three tier architecture and I have business object classes to represent entities such as User, Orders, UserType etc. In these classes I have methods that are executed when the Constuctor method of, for example, User is called. These methods perform calculations and generate details that setup data for attributes that are part of each User object. Here is the structure for the project in Visual Studio: Here is some code from the business object class User.cs: Public Class User { public string Name { get; set; } public int RandomNumber { get; set; } etc public User { Name = GetName(); RandomNumber = GetRandomNumber(); } public string GetName() { .... return name; } public int GetRandomNumber() { ... return randomNumber; } } Should this logic be included in the Business Object classes or should it be included in a Utilities class of some kind? Or in the business rules?

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  • How to pass an interface to Java from Unity code?

    - by nickbadal
    First, let me say that this is my first experience with Unity, so the answer may be right under my nose. I've also posted this question on Unity's answers site, but plugin questions don't seem to be as frequently answered there. I'm trying to create a plugin that allows me to access an SDK from my game. I can call SDK methods just fine using AndroidJavaObject and I can pass data to them with no issue. But there are some SDK methods that require an interface to be passed. For example, my Java function: public void attemptLogin(String username, String password, LoginListener listener); Where listener; is a callback interface. I would normally run this code from Java as such: attemptLogin("username", "password", new LoginListener() { @Override public void onSuccess() { //Yay! do some stuff in the game } @Override public void onFailure(int error) { //Uh oh, find out what happened based on error } }); Is there a way to pass a C# interface through JNI/Unity to my attemptLogin function? Or is there a way to create a mimic-ing interface in C# that I can call from inside the Java code (and pass in any kind of parameter)? Thanks in advance! :)

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  • Motivation for a service layer (instead of just copying dlls)?

    - by BornToCode
    I'm creating an application which has 2 different UIs so I'm making it with a service layer which I understood is appropriate for such scenario. However I found myself just creating web methods for every single method I have in the BL layer, so the services basically built from methods that looks like this: return customers_bl.Get_Customer_Prices(customer_id); I understood that a main point of the service layer is to prevent duplication of code so I asked myself - why not just import the BL.DLL (and the dal.dll) to the other UI, and whenever making a change re-copy the dlls, it might not be so 'neat', but still less hassle than one more layer? {I know something is wrong in my approach, I'm probably missing the importance of service layer, I'd like to get more motivation to create another layer, especially because as it is I found that many of my BL functions ALREADY looks like: return customers_dal.Get_Customer_Prices(cust_id) which led me to ask: was it really necessary to create the BL just because on several functions I actually have LOGIC inside the BL?} so I'm looking for more motivation to creating ONE MORE layer, I'm sure it's not just to make it more convenient that I won't have to re-copy the dlls on changes? Am I grasping it wrong? Any simple guidelines on how to design service layer (corresponding to all the BL layer functions or not? any simple example?) any enlightenment on the subject?

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  • Combinatorial explosion of interfaces: How many is too many?

    - by mga
    I'm a relative newcomer to OOP, and I'm having a bit of trouble creating good designs when it comes to interfaces. Consider a class A with N public methods. There are a number of other classes, B, C, ..., each of which interacts with A in a different way, that is, accesses some subset (<= N) of A's methods. The maximum degree of encapsulation is achieved by implementing an interface of A for each other class, i.e. AInterfaceForB, AInterfaceForC, etc. However, if B, C, ... etc. also interact with A and with each other, then there will be a combinatorial explosion of interfaces (a maximum of n(n-1), to be precise), and the benefit of encapsulation becomes outweighed by a code-bloat. What is the best practice in this scenario? Is the whole idea of restricting access to a class's public functions in different ways for other different classes just silly altogether? One could imagine a language that explicitly allows for this sort of encapsulation (e.g. instead of declaring a function public, one could specify exactly which classes it is visible to); Since this is not a feature of C++, maybe it's misguided to try to do it through the back door with interaces?

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  • I cannot change the grub Default item from OS-1, but I can from OS-2 (dual-boot 10.04 on both)

    - by fred.bear
    My 10.04 system (OS-1) got into a tangle the other day, so I installed a second, dual-boot 10.04 (OS-2), so that I could trouble-shoot the hung system... In case it is relevant to my question, I'll mention that since I got OS-1 working again, it has shown a few battle wounds from its ordeal (.. actually the ordeal was mine ... trying to figure it all out ;) ... I lost some custom settings, but not all. (For the curious: the hangup was caused by rsync writing 600 GB to OS-1's 320 GB drive.. The destination drive was unmounted at the time, and rsync dutifully wrote directly to /media/usb_back; filling it to capacity... I have since, ammended my script :) Because the dual-boot MBR was prepared by OS-2, it is first on the grub list.. However, I want OS-1 to be the default OS to boot... From OS-1, I tried two methods to change the grub-menu's defaule OS. eg. Directly editing /etc/default/grub (then update-grub) Running 'Startup Manager' (then update-grub) Neither of these methods had any effect... so I started OS-2, and tried method 1... It worked! Why can I not change the grub menu from OS-1? .. or if it can be done, How?

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  • Create a rectangle struct to be rotated and have a .Intersects() function

    - by MintyAnt
    In my XNA program, I am trying to swing a sword. The sword starts at an angle of 180 degrees, then rotates (clockwise) to an angle of 90 degrees. The Rectangle struct that XNA provides, Rectangle mAttackBox = new Rectangle(int x, int y, int width, int height); However, this struct has two problems: Holds position and size in Integers, not Floats Cannot be rotated I was hoping someone could help me in either telling me that i'm wrong and the Rectangle can be used for both these methods, or can lead me down the right path for rotating a rectangle. I know how to create a Struct. I believe that I can make methods like classes. I can determine the 4 vertices of a 2D rectangle by calculating out the x,y of the other 3 given the length, width. I'm sure theres a Matrix class I can use to multiply each point against a Rotation matrix. But once i have my 4 vertices, I got two other problems: - How do I test other rectangles against it? How does .Intersects() work for the rectangle struct? - Is this even the fastest way to do it? I'd be constantly doing matrix multiplication, wouldnt that slow things down?

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  • In developing a soap client proxy, which return structure is easier to use and more sensible?

    - by cori
    I'm writing (in PHP) a client/proxy for a SOAP web service. The return types are consistently wrapped in response objects that contain the return values. In many cases this make a lot of sense - for instance when multiple values are being returned: GetDetailsResponse Object ( Results Object ( [TotalResults] => 10 [NextPage] => 2 ) [Details] => Array ( [0] => Detail Object ( [Id] => 1 ) ) ) But some of the methods return a single scalar value or a single object or array wrapped in a response object: GetThingummyIdResponse Object ( [ThingummyId] => 42 ) In some cases these objects might be pretty deep, so getting at properties within requires drilling down several layers: $response->Details->Detail[0]->Contents->Item[5]->Id And if I unwrap them before passing them back I can strip out a layer from consumers' code. I know I'm probably being a little bit of an Architecture Astronaut here, but the latter style really bug me, so I've been working through my code to have my proxy methods just return the scalar value to the client code where there's no absolute need for a wrapper object. My question is, am I actually making things more difficult for the consumers of my code? Would I be better off just leaving the return values wrapped in response objects so that everything is consistent, or is removing unneccessary layers of indirection/abstraction worthwhile?

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  • Using the Coherence ConcurrentMap Interface (Locking API)

    - by jpurdy
    For many developers using Coherence, the first place they look for concurrency control is the com.tangosol.util.ConcurrentMap interface (part of the NamedCache interface). The ConcurrentMap interface includes methods for explicitly locking data. Despite the obvious appeal of a lock-based API, these methods should generally be avoided for a variety of reasons: They are very "chatty" in that they can't be bundled with other operations (such as get and put) and there are no collection-based versions of them. Locks do directly not impact mutating calls (including puts and entry processors), so all code must make explicit lock requests before modifying (or in some cases reading) cache entries. They require coordination of all code that may mutate the objects, including the need to lock at the same level of granularity (there is no built-in lock hierarchy and thus no concept of lock escalation). Even if all code is properly coordinated (or there's only one piece of code), failure during updates that may leave a collection of changes to a set of objects in a partially committed state. There is no concept of a read-only lock. In general, use of locking is highly discouraged for most applications. Instead, the use of entry processors provides a far more efficient approach, at the cost of some additional complexity.

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  • Interfaces: profit of using

    - by Zapadlo
    First of all, my ubiquitous language is PHP, and I'm thinking about learning Java. So let me split my question on two closely related parts. Here goes the first part. Say I have a domain-model class. It has some getters, setters, some query methods etc. And one day I want to have a possibility to compare them. So it looks like: class MyEntity extends AbstractEntity { public function getId() { // get id property } public function setId($id) { // set id property } // plenty of other methods that set or retrieve data public function compareTo(MyEntity $anotherEntity) { // some compare logic } } If it would have been Java, I should have implemented a Comparable interface. But why? Polymorphism? Readbility? Or something else? And if it was PHP -- should I create Comparable interface for myself? So here goes the second part. My colleague told me that it is a rule of thumb in Java to create an interface for every behavioral aspect of the class. For example, if I wanted to present this object as a string, I should state this behaviour by something like implements Stringable, where in case of PHP Stringable would look like: interface Stringable { public function __toString(); } Is that really a rule of thumb? What benefits are gained with this approach? And does it worth it in PHP? And in Java?

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  • Adding functionality to any TextReader

    - by strager
    I have a Location class which represents a location somewhere in a stream. (The class isn't coupled to any specific stream.) The location information will be used to match tokens to location in the input in my parser, to allow for nicer error reporting to the user. I want to add location tracking to a TextReader instance. This way, while reading tokens, I can grab the location (which is updated by the TextReader as data is read) and give it to the token during the tokenization process. I am looking for a good approach on accomplishing this goal. I have come up with several designs. Manual location tracking Every time I need to read from the TextReader, I call AdvanceString on the Location object of the tokenizer with the data read. Advantages Very simple. No class bloat. No need to rewrite the TextReader methods. Disadvantages Couples location tracking logic to tokenization process. Easy to forget to track something (though unit testing helps with this). Bloats existing code. Plain TextReader wrapper Create a LocatedTextReaderWrapper class which surrounds each method call, tracking a Location property. Example: public class LocatedTextReaderWrapper : TextReader { private TextReader source; public Location Location { get; set; } public LocatedTextReaderWrapper(TextReader source) : this(source, new Location()) { } public LocatedTextReaderWrapper(TextReader source, Location location) { this.Location = location; this.source = source; } public override int Read(char[] buffer, int index, int count) { int ret = this.source.Read(buffer, index, count); if(ret >= 0) { this.location.AdvanceString(string.Concat(buffer.Skip(index).Take(count))); } return ret; } // etc. } Advantages Tokenization doesn't know about Location tracking. Disadvantages User needs to create and dispose a LocatedTextReaderWrapper instance, in addition to their TextReader instance. Doesn't allow different types of tracking or different location trackers to be added without layers of wrappers. Event-based TextReader wrapper Like LocatedTextReaderWrapper, but decouples it from the Location object raising an event whenever data is read. Advantages Can be reused for other types of tracking. Tokenization doesn't know about Location tracking or other tracking. Can have multiple, independent Location objects (or other methods of tracking) tracking at once. Disadvantages Requires boilerplate code to enable location tracking. User needs to create and dispose the wrapper instance, in addition to their TextReader instance. Aspect-orientated approach Use AOP to perform like the event-based wrapper approach. Advantages Can be reused for other types of tracking. Tokenization doesn't know about Location tracking or other tracking. No need to rewrite the TextReader methods. Disadvantages Requires external dependencies, which I want to avoid. I am looking for the best approach in my situation. I would like to: Not bloat the tokenizer methods with location tracking. Not require heavy initialization in user code. Not have any/much boilerplate/duplicated code. (Perhaps) not couple the TextReader with the Location class. Any insight into this problem and possible solutions or adjustments are welcome. Thanks! (For those who want a specific question: What is the best way to wrap the functionality of a TextReader?) I have implemented the "Plain TextReader wrapper" and "Event-based TextReader wrapper" approaches and am displeased with both, for reasons mentioned in their disadvantages.

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  • CSS/JavaScript/hacking: Detect :visited styling on a link *without* checking it directly OR do it fa

    - by Sai Emrys
    This is for research purposes on http://cssfingerprint.com Consider the following code: <style> div.csshistory a { display: none; color: #00ff00;} div.csshistory a:visited { display: inline; color: #ff0000;} </style> <div id="batch" class="csshistory"> <a id="1" href="http://foo.com">anything you want here</a> <a id="2" href="http://bar.com">anything you want here</a> [etc * ~2000] </div> My goal is to detect whether foo has been rendered using the :visited styling. I want to detect whether foo.com is visited without directly looking at $('1').getComputedStyle (or in Internet Explorer, currentStyle), or any other direct method on that element. The purpose of this is to get around a potential browser restriction that would prevent direct inspection of the style of visited links. For instance, maybe you can put a sub-element in the <a> tag, or check the styling of the text directly; etc. Any method that does not directly or indierctly rely on $('1').anything is acceptable. Doing something clever with the child or parent is probably necessary. Note that for the purposes of this point only, the scenario is that the browser will lie to JavaScript about all properties of the <a> element (but not others), and that it will only render color: in :visited. Therefore, methods that rely on e.g. text size or background-image will not meet this requirement. I want to improve the speed of my current scraping methods. The majority of time (at least with the jQuery method in Firefox) is spent on document.body.appendChild(batch), so finding a way to improve that call would probably most effective. See http://cssfingerprint.com/about and http://cssfingerprint.com/results for current speed test results. The methods I am currently using can be seen at http://github.com/saizai/cssfingerprint/blob/master/public/javascripts/history_scrape.js To summarize for tl;dr, they are: set color or display on :visited per above, and check each one directly w/ getComputedStyle put the ID of the link (plus a space) inside the <a> tag, and using jQuery's :visible selector, extract only the visible text (= the visited link IDs) FWIW, I'm a white hat, and I'm doing this in consultation with the EFF and some other fairly well known security researchers. If you contribute a new method or speedup, you'll get thanked at http://cssfingerprint.com/about (if you want to be :-P), and potentially in a future published paper. ETA: The bounty will be rewarded only for suggestions that can, on Firefox, avoid the hypothetical restriction described in point 1 above, or perform at least 10% faster, on any browser for which I have sufficient current data, than my best performing methods listed in the graph at http://cssfingerprint.com/about In case more than one suggestion fits either criterion, the one that does best wins.

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