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• Objective C - Aggro with Images

  - by Will

  I have three UIImageViews. enemy1, enemy1AggroBox and mainSprite. What I want to do is when mainSprite and enemy1AggroBox interect, I want enemy1 to start moving towards mainSprite. Basically creating aggro for a game. if(CGRectIntersectsRect(mainSprite.frame, enemy1AggroBox.frame)){ //Code here// } My plan would be to call this method in viewDidLoad. I'm not using any sort of framework like cocos2d or OpenGLES. If you need to see any more code just ask.

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• Preffered lambda syntax?

  - by Roger Alsing

  I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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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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• When do you use a struct instead of a class?

  - by jkohlhepp

  What are your rules of thumb for when to use structs vs. classes? I'm thinking of the C# definition of those terms but if your language has similar concepts I'd like to hear your opinion as well. I tend to use classes for almost everything, and use structs only when something is very simplistic and should be a value type, such as a PhoneNumber or something like that. But this seems like a relatively minor use and I hope there are more interesting use cases.

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• Server-side Architecture for Online Game

  - by Draiken

  Hi, basically I have a game client that has communicate with a server for almost every action it takes, the game is in Java (using LWJGL) and right now I will start making the server. The base of the game is normally one client communicating with the server alone, but I will require later on for several clients to work together for some functionalities. I've already read how authentication server should be sepparated and I intend on doing it. The problem is I am completely inexperienced in this kind of server-side programming, all I've ever programmed were JSF web applications. I imagine I'll do socket connections for pretty much every game communication since HTML is very slow, but I still don't really know where to start on my server. I would appreciate reading material or guidelines on where to start, what architecture should the game server have and maybe some suggestions on frameworks that could help me getting the client-server communication. I've looked into JNAG but I have no experience with this kind of thing, so I can't really tell if it is a solid and good messaging layer. Any help is appreciated... Thanks !

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• Java Desktop Application For Network users

  - by Motasem Abu Aker

  I'm developing a desktop application using Java. My application will run in a network environment where multiple users will access the same database through the application. There will be basic CRUD opreations (Insert, Update, Delete, & select), which means there will be chances of deadlock, or two users trying to update the same record at same time. I'm using the following Java Swing for Clients (MVC). MySQL Server for database (InnODB). Java Web start. Now, MySQL is centralized on the network, and all of the clients connect to it. The Application for ERP Purpose. I searched the internet to find a very good solution to ensure data integrity & to make sure that when updating one record from one client, other clients are aware of it. I read about Socket-server-client & RESTful web services. I don't want to go web application & don't want to use any extra libraries. So how can I handle this scenario: If User A updates a record: Is there a way to update User B's screen with the new value? If user A starts updating a record, how can I prevent other users from attempting to update the same record?

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• When is a Use Case layer needed?

  - by Meta-Knight

  In his blog post The Clean Architecture Uncle Bob suggests a 4-layer architecture. I understand the separation between business rules, interfaces and infrastructure, but I wonder if/when it's necessary to have separate layers for domain objects and use cases. What added value will it bring, compared to just having the uses cases as "domain services" in the domain layer? The only useful info I've found on the web about a use case layer is an article by Martin Fowler, who seems to contradict Uncle Bob about its necessity: At some point I may run into the problems, and then I'll make a Use Case Controller - but only then. And even when I do that I rarely consider the Use Case Controllers to occupy a separate layer in the system architecture. Edit: I stumbled upon a video of Uncle Bob's Architecture: The Lost Years keynote, in which he explains this architecture in depth. Very informative.

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• Requiring multithreading/concurrency for implementation of scripting language

  - by Ricky Stewart

  Here's the deal: I'm looking at designing my own scripting/interpreted language for fun. I'm only in the planning stages right now; I want to make sure I have a very strong hold on exactly how I will implement everything before I start coding. What I'm currently struggling with is concurrency. It seems to me like an easy way to avoid the unpredictable performance that comes with garbage collection would be to put the garbage collector in its own thread, and have it run concurrently with the interpreter itself. (To be clear, I don't plan to allow the scripts to be multithreaded themselves; I would simply put a garbage collector to work in a different thread than the interpreter.) This doesn't seem to be a common strategy for many popular scripting languages, probably for portability reasons; I would probably write the interpreter in the UNIX/POSIX threading framework initially and then port it to other platforms (Windows, etc.) if need be. Does anyone have any thoughts in this issue? Would whatever gains I receive by exploiting concurrency be nullified by the portability issues that will inevitably arise? (On that note, am I really correct in my assumption that I would experience great performance gains with a concurrent garbage collector?) Should I move forward with this strategy or step away from it?

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• Examples of Liskov Substitution

  - by james lewis

  I'm facilitating a session next week on the Liskov Substitution Principle and I was wondering if anyone had any examples of violations 'from the trenches'? I'm looking for something other than uncle Bob's rectangle - square problem and the persistent set problem he talks about in A-PPP (although that is a great example). So far I'm using the example of a (very simple) List and an IndexedList as the 'correct' use of inheritance. And the addition of a Set to this hierarchy as a violation (as a Set is distinct; strengthening the pre condition of the Add method). I've also taken this great example and it's solution from this question Both those examples are great but I'm looking for something more subtle and harder to spot. So far I've come up with nothing so if you've got a great, subtle example post it up. Also, any metaphors you've come across that helped you understand LSP would be really useful too.

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• Good free CSS Sprite for icons

  - by Saif Bechan

  I am working on a small project where I need some of the basic icons: edit, favorite, delete. You know them. Now i can download them all seperate, and put them together in a sprite, but I was wondering if there are ready to download sprites which I can use. Now I am working on an accounting app, so it would be nice if the icons were not too childish. A little but of fancy business type icons. Thanks

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• How to Detect Sprites in a SpriteSheet?

  - by IAE

  I'm currently writing a Sprite Sheet Unpacker such as Alferds Spritesheet Unpacker. Now, before this is sent to gamedev, this isn't necessarily about games. I would like to know how to detect a sprite within a spriitesheet, or more abstactly, a shape inside of an image. Given this sprite sheet: I want to detect and extract all individual sprites. I've followed the algorithm detailed in Alferd's Blog Post which goes like: Determine predominant color and dub it the BackgroundColor Iterate over each pixel and check ColorAtXY == BackgroundColor If false, we've found a sprite. Keep going right until we find a BackgroundColor again, backtrack one, go down and repeat until a BackgroundColor is reached. Create a box from location to ending location. Repeat this until all sprites are boxed up. Combined overlapping boxes (or within a very short distance) The resulting non-overlapping boxes should contain the sprite. This implementation is fine, especially for small sprite sheets. However, I find the performance too poor for larger sprite sheets and I would like to know what algorithms or techniques can be leveraged to increase the finding of sprites. A second implementation I considered, but have not tested yet, is to find the first pixel, then use a backtracking algorithm to find every connected pixel. This should find a contiguous sprite (breaks down if the sprite is something like an explosion where particles are no longer part of the main sprite). The cool thing is that I can immediately remove a detected sprite from the sprite sheet. Any other suggestions?

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• Object behaviour or separate class?

  - by Andrew Stephens

  When it comes to OO database access you see two common approaches - the first is to provide a class (say "Customer") with methods such as Retrieve(), Update(), Delete(), etc. The other is to keep the Customer class fairly lightweight (essentially just properties) and perform the database access elsewhere, e.g. using a repository. This choice of approaches doesn't just apply to database access, it can crop up in many different OOD scenarios. So I was wondering if one way is preferable over the other (although I suspect the answer will be "it depends")! Another dev on our team argues that to be truly OO the class should be "self-contained", i.e. providing all the methods necessary to manipulate and interact with that object. I personally prefer the repository approach - I don't like bloating the Customer class with all that functionality, and I feel it results in cleaner code having it elsewhere, but I can't help thinking I'm seriously violating core OO concepts! And what about memory implications? If I retrieve thousands of Customer objects I'm assuming those with the data access methods will take up a lot more memory than the property-only objects?

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• Presenting at Roanoke Code Camp Saturday!

  - by andyleonard

  Introduction I am honored to once again be selected to present at Roanoke Code Camp ! An Introductory Topic One of my presentations is titled "I See a Control Flow Tab. Now What?" It's a Level 100 talk for those wishing to learn how to build their very first SSIS package. This highly-interactive, demo-intense presentation is for beginners and developers just getting started with SSIS. Attend and learn how to build SSIS packages from the ground up . Designing an SSIS Framework I'm also presenting...(read more)

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• Join Me May 19th for 24 Hours of PASS

  - by KKline

  Check out all the great SQL Server sessions you can attend for FREE in this on-line event....(read more)

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• Starting point for a simple game written in action script [closed]

  - by Hossein

  Possible Duplicate: AS3/Flash Game Dev: Looking for good & current step by step. Hi, I want to develop a simple game like: http://www.albinoblacksheep.com/games/falldown2 And then making it a bit more fancy. But I don't know where to start. I have already started AS3 so I know about the syntax and stuff, but I am kinda lost. Does anyone knows of a nice starting point or a tutorial that can help me with this? Thanks

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• What to include in metadata?

  - by shyam

  I'm wondering if there are any general guidelines or best practices regarding when to split data into a metadata format, as oppose to directly embedding it within the data. (Specific example below). My understanding of metadata is that it describes data (without the need to actually look at the data), allowing for data to be quickly search/filtered for easy access. Let's take for example a simple 3D model format. The actual data file itself is a binary file containing vertices and colors. Things like creation date, modified data and author name would be things that describe the binary data, so I would say these belong as metadata (outside of the binary file). But what if the application had no need to search or filter by these fields? Would it be acceptable to embed these fields directly into the binary data itself? Could they be duplicated in both the binary data and the meta data, or would this be considered bad practice? What about more ambiguous fields such as the model name, which could be considered part of the data itself, but also as data describing the binary data?... How do you decide which data to embed in the actual binary file, as opposed to separating into a more flexible metadata format? Thanks!

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• 2D pathfinding - finding smooth paths

  - by Kooi Nam Ng

  I was trying to implement a simple pathfinding, but the outcome is less satisfactory than what I intended to achieve. The thing is units in games like Starcraft 2 move in all directions whereas units in my case only move in at most 8 directions (Warcraft 1 style) as these 8 directions direct to next available nodes (they move from a tile to next neighboring tile). What should I do in order to achieve the result as in Starcraft 2? Shrink the tile size? On the picture you can see a horizontal line of rock tiles being obstacles, and the found path marked as green tiles. The red line is the path I want to achieve.

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• How to refactor and improve this XNA mouse input code?

  - by Andrew Price

  Currently I have something like this: public bool IsLeftMouseButtonDown() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Pressed; } public bool IsLeftMouseButtonPressed() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonUp() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonReleased() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Pressed; } This is fine. In fact, I kind of like it. However, I'd hate to have to repeat this same code five times (for right, middle, X1, X2). Is there any way to pass in the button I want to the function so I could have something like this? public bool IsMouseButtonDown(MouseButton button) { return currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonPressed(MouseButton button) { return currentMouseState.IsPressed(button) && !previousMouseState.IsPressed(button); } public bool IsMouseButtonUp(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonReleased(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } I suppose I could create some custom enumeration and switch through it in each function, but I'd like to first see if there is a built-in solution or a better way.. Thanks!

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• Variable declaration versus assignment syntax

  - by rwallace

  Working on a statically typed language with type inference and streamlined syntax, and need to make final decision about syntax for variable declaration versus assignment. Specifically I'm trying to choose between: // Option 1. Create new local variable with :=, assign with = foo := 1 foo = 2 // Option 2. Create new local variable with =, assign with := foo = 1 foo := 2 Creating functions will use = regardless: // Indentation delimits blocks square x = x * x And assignment to compound objects will do likewise: sky.color = blue a[i] = 0 Which of options 1 or 2 would people find most convenient/least surprising/otherwise best?

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• Overloading interface buttons, what are the best practices?

  - by XMLforDummies

  Imagine you'll have always a button labeled "Continue" in the same position in your app's GUI. Would you rather make a single button instance that takes different actions depending on the current state? private State currentState = State.Step1; private ContinueButton_Click() { switch(currentState) { case State.Step1: DoThis(); currentState = State.Step2; break; case State.Step2: DoThat(); break; } } Or would you rather have something like this? public Form() { this.ContinueStep2Button.Visible = false; } private ContinueStep1Button_Click() { DoThis(); this.ContinueStep1Button.Visible = false; this.ContinueStep2Button.Visible = true; } private ContinueStep2Button_Click() { DoThat(); }

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• Is true multithreading really necessary?

  - by Jonathan Graef

  So yeah, I'm creating a programming language. And the language allows multiple threads. But, all threads are synchronized with a global interpreter lock, which means only one thread is allowed to execute at a time. The only way to get the threads to switch off is to explicitly tell the current thread to wait, which allows another thread to execute. Parallel processing is of course possible by spawning multiple processes, but the variables and objects in one process cannot be accessed from another. However the language does have a fairly efficient IPC interface for communicating between processes. My question is: Would there ever be a reason to have multiple, unsynchronized threads within a single process (thus circumventing the GIL)? Why not just put thread.wait() statements in key positions in the program logic (presuming thread.wait() isn't a CPU hog, of course)? I understand that certain other languages that use a GIL have processor scheduling issues (cough Python), but they have all been resolved.

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• Is Paypal the best solution for payment gateway for a website?

  - by Pennf0lio

  I have a realty website that needs a payment gateway for their property reservation. The reservation fee range from $500-$600 and about 5-6 people per month. I was wondering if Paypal is the best solution for accepting Payment. What will be the Pros and Cons using Paypal. Paypal was my first choice because It's easy to integrate on my existing website and I wouldn't be minding so much on the security. P.S. It's not a part of the question, But If you can site some realty website that accept payment and would be a good inspiration. It would be highly appreciated. Thanks!

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• Would you use UML if it kept stakeholders from requesting changes frequently?

  - by Huperniketes

  As much as programmers hate to document their code/system and draw UML (especially, Sequencing, Activity and State machine diagrams) or other diagramming notation, would you agree to do it if it kept managers from requesting a "minor change" every couple of weeks? IOW, would you put together visual models to document the system if it helped you demonstrate to managers what the effect of changes are and why it takes so long to implement them? (Edited to help programmers understand what type of answer I'm looking for.) 2nd edit: Restating my question again, "Would you be willing to use some diagramming notation, against your better nature as a programmer, if it helped you manage change requests?" This question isn't asking if there might be something wrong with the process. It's a given that there's something wrong with the process. Would you be willing to do more work to improve it?

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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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• Help me select a "Simpler" target to create a new language: .NET, LLVM, Go, Own VM

  - by mamcx

  Lets define "Simple". This is my first language. I have no previous experience I will not dedicate +4 years to learn it properly. I'm a professional software [developer], but as an amateur in this area, I want instant gratification. If the idea shows a future, I could rewrite it. I don't want to do everything from scratch. In fact, if there exists a way to get GO (for example), change its syntax, add some sugar, give some extra functions and leave intact everything else, that would be perfect! From the example of coffescript/scala I think is better to build on top of some rich runtime like .NET/GO so I don't need to rewrite everything. HOWEVER, if is better other way, no problem for the first try! I want it in a week. I need it in a week so it will really take a month. Then it truly takes 3 months. But I don't want to put more that 3 months on this. I could reduce the scope of my language, but I hope the tools will help me a lot... I want to build a new language. Similar to python, but typed. I wonder what to build it on top of. I like the idea of building on top of GO. To get their sane (IMHO) OO paradigm (I plan to do the same, using interfaces, not inheritance), get goroutines and some other stuff. In my naive thinking I imagine that spit another language could help me to debug it more easily. However, look like everyone is building on top of something like .NET (don't like Java), LLVM or make it own VM. I read http://createyourproglang.com/ (great!) and the part of the VM look "easy" to me. So, what I need is the proper criteria and question I need to know in advance to have a fair shot at make this.

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