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  • null values vs "empty" singleton for optional fields

    - by Uko
    First of all I'm developing a parser for an XML-based format for 3D graphics called XGL. But this question can be applied to any situation when you have fields in your class that are optional i.e. the value of this field can be missing. As I was taking a Scala course on coursera there was an interesting pattern when you create an abstract class with all the methods you need and then create a normal fully functional subclass and an "empty" singleton subclass that always returns false for isEmpty method and throws exceptions for the other ones. So my question is: is it better to just assign null if the optional field's value is missing or make a hierarchy described above and assign it an empty singleton implementation?

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  • Simplifying C++11 optimal parameter passing when a copy is needed

    - by Mr.C64
    It seems to me that in C++11 lots of attention was made to simplify returning values from functions and methods, i.e.: with move semantics it's possible to simply return heavy-to-copy but cheap-to-move values (while in C++98/03 the general guideline was to use output parameters via non-const references or pointers), e.g.: // C++11 style vector<string> MakeAVeryBigStringList(); // C++98/03 style void MakeAVeryBigStringList(vector<string>& result); On the other side, it seems to me that more work should be done on input parameter passing, in particular when a copy of an input parameter is needed, e.g. in constructors and setters. My understanding is that the best technique in this case is to use templates and std::forward<>, e.g. (following the pattern of this answer on C++11 optimal parameter passing): class Person { std::string m_name; public: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> explicit Person(T&& name) : m_name(std::forward<T>(name)) { } ... }; A similar code could be written for setters. Frankly, this code seems boilerplate and complex, and doesn't scale up well when there are more parameters (e.g. if a surname attribute is added to the above class). Would it be possible to add a new feature to C++11 to simplify code like this (just like lambdas simplify C++98/03 code with functors in several cases)? I was thinking of a syntax with some special character, like @ (since introducing a &&& in addition to && would be too much typing :) e.g.: class Person { std::string m_name; public: /* Simplified syntax to produce boilerplate code like this: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> */ explicit Person(std::string@ name) : m_name(name) // implicit std::forward as well { } ... }; This would be very convenient also for more complex cases involving more parameters, e.g. Person(std::string@ name, std::string@ surname) : m_name(name), m_surname(surname) { } Would it be possible to add a simplified convenient syntax like this in C++? What would be the downsides of such a syntax?

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  • Gamification: designing cooperation in an RPG like game based on Scrum methodology

    - by Grzegorz Slawecki
    I have implemented with 3 friends a gamified system at my work (development company) which builds an fantasy rpg game over scrum project methodology. Generally, the tasks are the missions, each player is represented by a character. They earn XPs for completing tasks and they advance to the next levels which gives them badges, titles and (this is in planning phase) new privileges (e.g. priority in choosing tasks). Since the very beginning we try to do everything to avoid rivalisation between players because it would ruin the project if the players started to compete. There are no explicit leaderboards, we also plan to give bonuses for helping other players. I have a feeling that this is still not enough to really encourage cooperation. I would like to ask You for any ideas that come to Your mind that would help.

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  • Create Outlook Appointments from PowerShell

    - by BuckWoody
    I've been toying around with a script to create a special set of calendar objects in Outlook that show when my SQL Server Agent Jobs are scheduled to run. I haven't finished yet, but I thought I would share the part that creates the Outlook Appointments.I have yet to fill a variable with the start and end times, and then loop through that to create the appointments. I'm thinking I'll make the script below into a function, and feed it those variables in a loop. The script below creates a whole new Calendar Folder in Outlook called "SQL Server Agent Jobs". I also use categories quite a bit, so you'll see that too. Caution: If you plan to play with this script, do it on an isolated workstation, not on your "regular" Outlook calendar. Otherwise, you'll have lots of appointments in there that you don't care about!  # Add a new calendar item to a new Outlook folder called "SQL Server Agent Jobs" $outlook = new-object -com Outlook.Application $calendar = $outlook.Session.folders.Item(1).Folders.Item("SQL Server Agent Jobs") $appt = $calendar.Items.Add(1) # == olAppointmentItem $appt.Start = [datetime]"03/11/2010 11:00" $appt.End = [datetime]"03/11/2009 12:00" $appt.Subject = "JobName" $appt.Location = "ServerName" $appt.Body = "Job Details" $appt.Categories = "SQL server Agent Job" $appt.Save()   Script Disclaimer, for people who need to be told this sort of thing: Never trust any script, including those that you find here, until you understand exactly what it does and how it will act on your systems. Always check the script on a test system or Virtual Machine, not a production system. All scripts on this site are performed by a professional stunt driver on a closed course. Your mileage may vary. Void where prohibited. Offer good for a limited time only. Keep out of reach of small children. Do not operate heavy machinery while using this script. If you experience blurry vision, indigestion or diarrhea during the operation of this script, see a physician immediately.   Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Push or Pull Input Data In the Game Logic?

    - by Qua
    In the process of preparing my game for networking I'm adding a layer of seperation between the physical input (mouse/keyboard) and the actual game "engine"/logic. All input that has any relation to the game logic is wrapped inside action objects such as BuildBuildingAction. I was thinking of having an action processing layer that would determine what to do with the input. This layer could then be set up to either just pass the actions locally to the game engine or send it via sockets to the network server depending on whether the game was single- or multiplayer. In network games it would make sense that the player's actions should be sent to the server, but should the game logic be pulling (polling?) the data through some sort of interface or should the action processing layer be adding the actions to an input queue in the game logic code?

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  • how do you read from system.out in Java [closed]

    - by Dan
    I'm trying to create a word scramble game and so far I have taken a vector of randomly assorted strings that contains both words and hints and split them into two vectors. I have randomly scrambled the word and set this all up in text boxes. Right now I'm stuck because I have a text box that takes input but I'm not sure how to read that in? I want the user to type the unscrambled word into the text box and have it calculate as correct and move on to the next word immediately. I also don't know how to get the keys working. I want the "?" character to be the hint button that shows the hint. At the moment the hint box works if I type the question mark in using the System.in but it doesn't work if I type it directly in to the text box. The characters are showing up in the text box but nothing is working after that.

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  • What good books are out there on program execution models? [on hold]

    - by murungu
    Can anyone out there name a few books that address the topic of program execution models?? I want a book that can answer questions such as... What is the difference between interpreted and compiled languages and what are the performance consequences at runtime?? What is the difference between lazy evaluation, eager evaluation and short circuit evaluation?? Why would one choose to use one evaluation strategy over another?? How do you simulate lazy evaluation in a language that favours eager evaluation??

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  • Why not expose a primary key

    - by Angelo Neuschitzer
    In my education I have been told that it is a flawed idea to expose actual primary keys (not only DB keys, but all primary accessors) to the user. I always thought it to be a security problem (because an attacker could attempt to read stuff not their own). Now I have to check if the user is allowed to access anyway, so is there a different reason behind it? Also, as my users have to access the data anyway I will need to have a public key for the outside world somewhere in between. Now that public key has the same problems as the primary key, doesn't it?

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  • What would a database look like if it were normalized to be completely abstracted? lets call it Max(n) normal form

    - by Doug Chamberlain
    edit: By simplest form i was not implying that it would be easy to understand. For instance, developing in low level assembly language is the simplest way to can develop code, but it is far from the easiest. Essentially, what I am asking is in math you can simplify a fraction to a point where it can no longer be simplfied. Can the same be true for a database and what would a database look like in its simplest, form?

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  • How can I make an MMORPG appeal to casual players?

    - by Philipp
    I believe that there is a significant market of players who would enjoy the exploration and interaction aspects of MMORPGs, but simply don't have the time for the endless grinding marathons which are part of the average MMORPG. MMORPGs are all about interaction between players. But when different players have different amounts of time to invest into a game, those with less time to spend will soon lack behind their power-leveling friends and won't be able to interact with them anymore. One way to solve this would be to limit the progress a player can achieve per day, so that it simply doesn't make sense to play more than one or two hours a day. But even the busiest casual players sometimes like to spend a whole sunday afternoon playing a video game. Just stopping them after two hours would be really frustrating. It also creates a pressure to use the daily progress limit every day, because otherwise the player would feel like wasting something. This pressure would be detrimental for casual gamers. What else could be done to level the playing field between those players who play 40+ hours a week and those who can't play more than 10?

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  • Map Library: Client-side or Server-side?

    - by Mahdi
    As I have already asked here, I have to implement a Multi-Platform Map application. Now I have Mapstraction as an option which uses Javascript to implement the desired functionality. My question is, "Is there any reason/benefit to implement such a library (let say, Adapters) in Server-side (in my case, PHP)?" As these maps are all based on Javascript, there is a big reason to use Javascript again to make the adapter also, so it would not be dependent to PHP, Java, or .NET for example. But is that all? I wish to hear your ideas and comments also. :)

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  • How do I start correctly in building database classes in c#?

    - by e4rthdog
    I am new in C# programming and in OOP. I need to dive into web applications for my company, and I need to do it fast and correct. So even that I know ASP.NET MVC is the way to go, I want to start with some simple applications with ASP.NET Webforms and then advance to MVC logic. Also regarding my db classes: I plan to create common database classes in order to be able to use them either from WinForms or ASP.NET applications. I also know that the way to go is to learn about ORM and EF. BUT I also want to start from where I am feeling comfortable and that is the traditional ADO.NET way. So about my Data Access Layer classes: Should I return my results in datasets or arraylists/lists? Should my methods do their own connect/disconnect from the db, or have separate methods and let the application maintain the connection?

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  • Creating user UI using Flixel

    - by Jamie Read
    I am new to game development but familiar with programming languages. I have started using Flixel and have a working Breakout game with score and lives. What I am trying to do is add a Start Screen before actually loading the game. I have a create function that adds all the game elements to the stage: override public function create():void // all game elements { How can I add this pre-load Start Screen? I'm not sure if I have to add in the code to this create function or somewhere else and what code to actually add. Eventually I would also like to add saving, loading, options and upgrades too. So any advice with that would be great. Here is my main game.as: package { import org.flixel.*; public class Game extends FlxGame { private const resolution:FlxPoint = new FlxPoint(640, 480); private const zoom:uint = 2; private const fps:uint = 60; public function Game() { super(resolution.x / zoom, resolution.y / zoom, PlayState, zoom); FlxG.flashFramerate = fps; } } } Thanks.

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  • What are the relative merits for implementing an Erlang-style "Continuation" pattern in C#

    - by JoeGeeky
    What are the relative merits (or demerits) for implementing an Erlang-style "Continuation" pattern in C#. I'm working on a project that has a large number of Lowest priority threads and I'm wondering if my approach may be all wrong. It would seem there is a reasonable upper limit to the number of long-running threads that any one Process 'should' spawn. With that said, I'm not sure what would signal the tipping-point for too many thread or when alternate patterns such as "Continuation" would be more suitable. In this case, many of the threads do a small amount of work and then sleep until woken to go again (Ex. Heartbeat, purge caches, etc...). This continues for the life of the Process.

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  • Publish/Subscribe/Request for exchange of big, complex, and confidential data?

    - by Morten
    I am working on a project where a website needs to exchange complex and confidential (and thus encrypted) data with other systems. The data includes personal information, technical drawings, public documents etc. We would prefer to avoid the Request-Reply pattern to the dependent systems (and there are a LOT of them), as that would create an awful lot of empty traffic. On the other hand, I am not sure that a pure Publisher/Subscriber pattern would be apropriate -- mainly because of the complex and bulky nature of the data to be exchanged. For that reason we have discussed the possibility of a "publish/subscribe/request" solution. The Publish/Subscribe part would be to publish a message to the dependent systems, that something is ready for pickup. The actual content is then picked up by old-school Request-Reply action. How does this sound to you?? Regards, Morten

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  • Conditions for a traditional friends system vs. open following system

    - by Dan
    I'm just curious for everyone who is developing social sites out there. When you build a method for connecting users, do you prefer to use a following-style system (follow me, you can see all of my information and I can just choose to follow you back), or instead do you choose to have a friends-style system (I have to allow you see all of my information on your homepage, even if it is open to the public, vise versa). Why and under what circumstances do you use each? How do you manage privacy between your users? Have you use another way to connect your users? Examples of what methods you've choose and how you manage the user's privacy (private by default vs open to the web) are awesome; it could show correlation and provides an actual look.

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  • Are there specific legal issues for web developers working on sex dating sites?

    - by YumYumYum
    Say I have created many ordinary websites which are not related to any dating/sexual content. Are the rules and regulations for a developer the same when making a sex-related dating site? I'm talking about a site where people meet together and get to know each other, with the intent of having a sexual relationship (you know what I mean), also featuring webcam sex, but not explicitly a porno site. Do such sites have any special legal issues for developers compared with non-sexual/dating sites?

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  • Trying to detect collision between two polygons using Separating Axis Theorem

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • Naming a predicate: "precondition" or "precondition_is_met"?

    - by RexE
    In my web app framework, each page can have a precondition that needs to be satisfied before it can be displayed to the user. For example, if user 1 and user 2 are playing a back-and-forth role-playing game, user 2 needs to wait for user 1 to finish his turn before he can take his turn. Otherwise, the user is displayed a waiting page. This is implemented with a predicate: def precondition(self): return user_1.completed_turn The simplest name for this API is precondition, but this leads to code like if precondition(): ..., which is not really obvious. Seems to me like it is more accurate to call it precondition_is_met(), but not sure about that either. Is there a best practice for naming methods like this?

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  • responsibility for storage

    - by Stefano Borini
    A colleague and I were brainstorming about where to put the responsibility of an object to store itself on the disk in our own file format. There are basically two choices: object.store(file) fileformatWriter.store(object) The first one gives the responsibility of serialization on the disk to the object itself. This is similar to the approach used by python pickle. The second groups the representation responsibility on a file format writer object. The data object is just a plain data container (eventually with additional methods not relevant for storage). We agreed on the second methodology, because it centralizes the writing logic from generic data. We also have cases of objects implementing complex logic that need to store info while the logic is in progress. For these cases, the fileformatwriter object can be passed and used as a delegate, calling storage operations on it. With the first pattern, the complex logic object would instead accept the raw file, and implement the writing logic itself. The first method, however, has the advantage that the object knows how to write and read itself from any file containing it, which may also be convenient. I would like to hear your opinion before starting a rather complex refactoring.

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  • Microkernel architectural pattern and applicability for business applications

    - by Pangea
    We are in the business of building customizable web applications. We have the core team that provides what we call as the core platform (provides services like security, billing etc.) on top of which core products are built. These core products are industry specific solutions like telecom, utility etc. These core products are later used by other teams to build customer specific solutions in a particular industry. Until now we have a loose separation between platform and core product. The customer specific solutions are build by customizing 20-40% of the core offering and re-packaging. The core-platform and core products are released together as monolithic apps (ear). I am looking to improvise the current situation so that there is a cleaner separation on these 3. This allows us to have evolve each of these 3 separately etc. I've read through the Mircokernel architecture and kind of felt that I can take apply the principles in my context. But most of my reading about this pattern is always in the context of operating systems or application servers etc. I am wondering if there are any examples on how that pattern was used for architecting business applications. Or you could provide some insight on how to apply that pattern to my problem.

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  • Solid principles vs YAGNI

    - by KeesDijk
    When do the SOLID principles become YAGNI? As programmers we make trade-offs all the time, between complexity, maintainability, time to build and so forth. Amongst others, two of the smartest guidelines for making choices are in my mind the SOLID principles and YAGNI. If you don't need it; don't build it, and keep it clean. Now for example, when I watch the dimecast series on SOLID, I see it starts out as a fairly simple program, and ends up as a pretty complex one (end yes complexity is also in the eye of the beholder), but it still makes me wonder: when do SOLID principles turn into something you don't need? All solid principles are ways of working that enable use to make changes at a later stage. But what if the problem to solve is a pretty simple one and it's a throwaway application, then what? Or are the SOLID principles something that always apply? As asked in the comments: Solid Principles YAGNI

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  • MVP Pattern Philsophical Question - Security Checking in UI

    - by Brian
    Hello, I have a philosophical question about the MVP pattern: I have a component that checks whether a user has access to a certain privilege. This privilege turns on or off certain UI features. For instance, suppose you have a UI grid, and for each row that gets bound, I do a security check to see if certain features in the grid should be enabled or disabled. There are two ways to do this: have the UI/view call the component's method, determine if it has access, and enable/disable or show/hide. The other is have the view fire an event to the presenter, have the presenter do the check and return the access back down to the view through the model or through the event arg. As per the MVP pattern, which component should security checks fit into, the presenter or the view? Since the view is using it to determine its accessibility, it seems more fitting in the view, but it is doing database checks and all inside this business component, and there is business logic there, so I can see the reverse argument too. Thoughts? Thanks.

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  • Help with this optimization

    - by Milo
    Here is what I do: I have bitmaps which I draw into another bitmap. The coordinates are from the center of the bitmap, thus on a 256 by 256 bitmap, an object at 0.0,0.0 would be drawn at 128,128 on the bitmap. I also found the furthest extent and made the bitmap size 2 times the extent. So if the furthest extent is 200,200 pixels, then the bitmap's size is 400,400. Unfortunately this is a bit inefficient. If a bitmap needs to be drawn at 500,500 and the other one at 300,300, then the target bitmap only needs to be 200,200 in size. I cannot seem to find a correct way to draw in the components correctly with a reduced size. I figure out the target bitmap size like this: float AvatarComposite::getFloatWidth(float& remainder) const { float widest = 0.0f; float widestNeg = 0.0f; for(size_t i = 0; i < m_components.size(); ++i) { if(m_components[i].getSprite() == NULL) { continue; } float w = m_components[i].getX() + ( ((m_components[i].getSprite()->getWidth() / 2.0f) * m_components[i].getScale()) / getWidthToFloat()); float wn = m_components[i].getX() - ( ((m_components[i].getSprite()->getWidth() / 2.0f) * m_components[i].getScale()) / getWidthToFloat()); if(w > widest) { widest = w; } if(wn > widest) { widest = wn; } if(w < widestNeg) { widestNeg = w; } if(wn < widestNeg) { widestNeg = wn; } } remainder = (2 * widest) - (widest - widestNeg); return widest - widestNeg; } And here is how I position and draw the bitmaps: int dw = m_components[i].getSprite()->getWidth() * m_components[i].getScale(); int dh = m_components[i].getSprite()->getHeight() * m_components[i].getScale(); int cx = (getWidth() + (m_remainderX * getWidthToFloat())) / 2; int cy = (getHeight() + (m_remainderY * getHeightToFloat())) / 2; cx -= m_remainderX * getWidthToFloat(); cy -= m_remainderY * getHeightToFloat(); int dx = cx + (m_components[i].getX() * getWidthToFloat()) - (dw / 2); int dy = cy + (m_components[i].getY() * getHeightToFloat()) - (dh / 2); g->drawScaledSprite(m_components[i].getSprite(),0.0f,0.0f, m_components[i].getSprite()->getWidth(),m_components[i].getSprite()->getHeight(),dx,dy, dw,dh,0); I basically store the difference between the original 2 * longest extent bitmap and the new optimized one, then I translate by that much which I would think would cause me to draw correctly but then some of the components look cut off. Any insight would help. Thanks

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  • Is it possible to calculate or mathematically prove if a game is balanced / fair?

    - by Lurca
    This question is not focussed on video games but games in general. I went to a boardgame trade fair yesterday and asked myself if there is a way to calculate the fairness of a game. Sure, some of them require a good portion of luck, but it might be possible to calculate if some character is overpowered. Especially in role-playing games and trading card games. How, for example, can the creators of "Magic: The Gathering" make sure that there isn't the "one card that beats them all", given the impressive number of available cards?

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