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  • Stack Trace Logger [migrated]

    - by Chris Okyen
    I need to write a parent Java class that classes using recursion can extend. The parent class will be be able to realize whenever the call stack changes ( you enter a method, temporarily leave it to go to another method call, or you are are finsihed with the method ) and then print it out. I want it to print on the console, but clear the console as well every time so it shows the stack horizantaly so you can see the height of each stack to see what popped off and what popped on... Also print out if a baseline was reached for recursive functions. First. How can I using the StackTraceElements and Thread classes to detect automatically whenever the stack has popped or pushed an element on without calling it manually? Second, how would I do the clearing thing? For instance , if I had the code: public class recursion(int i) { private static void recursion(int i) { if( i < 10) System.out.println('A'); else { recursion(i / 10 ); System.out.println('B'); } } public static void main(String[] argv) { recursion(102); } } It would need to print out the stack when entering main(), when entering recursion(102) from main(), when it enters recursion(102 / 10), which is recursion(10), from recursion(102), when it enters recursion(10 / 10), which is recursion(1) from recursion(10). Print out a message out when it reaches the baseline recursion(1).. then print out the stacks of reversed revisitation of function recursion(10), recursion(102) and main(). finally print out we are exiting main().

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  • How to read Scala code with lots of implicits?

    - by Petr Pudlák
    Consider the following code fragment (adapted from http://stackoverflow.com/a/12265946/1333025): // Using scalaz 6 import scalaz._, Scalaz._ object Example extends App { case class Container(i: Int) def compute(s: String): State[Container, Int] = state { case Container(i) => (Container(i + 1), s.toInt + i) } val d = List("1", "2", "3") type ContainerState[X] = State[Container, X] println( d.traverse[ContainerState, Int](compute) ! Container(0) ) } I understand what it does on high level. But I wanted to trace what exactly happens during the call to d.traverse at the end. Clearly, List doesn't have traverse, so it must be implicitly converted to another type that does. Even though I spent a considerable amount of time trying to find out, I wasn't very successful. First I found that there is a method in scalaz.Traversable traverse[F[_], A, B] (f: (A) => F[B], t: T[A])(implicit arg0: Applicative[F]): F[T[B]] but clearly this is not it (although it's most likely that "my" traverse is implemented using this one). After a lot of searching, I grepped scalaz source codes and I found scalaz.MA's method traverse[F[_], B] (f: (A) => F[B])(implicit a: Applicative[F], t: Traverse[M]): F[M[B]] which seems to be very close. Still I'm missing to what List is converted in my example and if it uses MA.traverse or something else. The question is: What procedure should I follow to find out what exactly is called at d.traverse? Having even such a simple code that is so hard analyze seems to me like a big problem. Am I missing something very simple? How should I proceed when I want to understand such code that uses a lot of imported implicits? Is there some way to ask the compiler what implicits it used? Or is there something like Hoogle for Scala so that I can search for a method just by its name?

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  • Textures quality issues with Libgdx

    - by user1876708
    I have drawn several vector objets and characters ( in Adobe Illustrator ) for my game on Android. They are all scalable at any size without any quality losses ( of course it's vector ^^ ). I have tried to simulate my gameboard directly on Illustrator just before setting my assests on libdgx to implement them in my game. I set all the objects at the good size, so that they fit perfectly on my XHDPI device I am running my test on. As you can see it works great ( for me at least ^^ ), the PNG quality is good for me, as expected ! So I have edited all my PNG at this size, set my assets on libgdx and build my game apk. And here is a screenshot of my gameboard ( don't pay attention at the differences of placing and objects, but check at the objets presents on both screenshot ). As you can see, I have a loss of my PNG quality in the game. It can be seen clealry on the hedgehog PNG, but also ( but not as obvious ) on the mushroom ( check at the outline ) and the hole PNG. If you really pay attention, on every objects, you can see pixels that are not visible on my first screenshot. And I just can't figure out why this is happening Oo If you have any ideas, you are very welcome ! Thanks. PS : You can check more clearly the 2 gameboard on this two links ( look at them at 100%, display at high resolution ) : Good quality link, from Illustrator Poor quality link, from the game Second phase of tests : We display an object ( the hedgehog ) on our main menu screen to see how it looks like. The things is that it looks like he is suppose to, which means, high quality with no pixels. The hedgehog PNG is coming from an atlas : layer.addActor(hedgehog); No loss of quality with this method So we think the problem is comming from the method we are using to display it on our gameboard : blocks[9][3] = new Block(TextureUtils.hedgehog, new Vector2(9, 3)); the block is getting the size from the vector we are associating to it, but we have a loss of quality with this method.

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  • Unity scaling instantiated GameObject at Start() doesn't "keep"

    - by Shivan Dragon
    I have a very simple scenario: A box-like Prefab which is imported from Blender automatically (I have the .blend file in the Assets folder). A script that has two public GameObject fields. In one I place the above prefab, and in the other I place a terrain object (which I've created in Unity's graphical view): public Collider terrain; public GameObject aStarCellHighlightPrefab; This script is attached to the camera. The idea is to have the Blender prefab instantiated, have the terrain set as its parent, and then scale said prefab instance up. I first did it like this, in the Start() method: void Start () { cursorPositionOnTerrain = new RaycastHit(); aStarCellHighlight = (GameObject)Instantiate(aStarCellHighlightPrefab, new Vector3(300,300,300), terrain.transform.rotation); aStarCellHighlight.name = "cellHighlight"; aStarCellHighlight.transform.parent = terrain.transform; aStarCellHighlight.transform.localScale = new Vector3(100,100,100); } and first thought it didn't work. However later I noticed that it did in fact work, in the sense where the scale was applied right at the start, but then right after the prefab instance came back to its initial scale. Putting the scale code in the Update() methods fixes it in the sense where now it stays scaled all the time: void Update () { aStarCellHighlight.transform.localScale = new Vector3(100,100,100); //... } However I've noticed that when I run this code, the object is first displayed without the scale being applied, and it takes about 5-10 seconds for the scale to happen. During this time everything works fine (like input and logging, etc). The scene is very simple, it's not like it has a lot of stuff to load or anything (there's a Ray cast from the camera on to the terrain, but that seems to happen without such delays). My (2 part) question is: Why doesn't it take the scale transform when I do it at the beginning in the Start() method. Why do I have to keep scaling it in the Update() method? Why does it take so long for the scale to "apply/show up".

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  • PHP MYSQL loop to check if LicenseID Values are contained in mysql DB [closed]

    - by Jasper
    I have some troubles to find the right loop to check if some values are contained in mysql DB. I'm making a software and I want to add license ID. Each user has x keys to use. Now when the user start the client, it invokes a PHP page that check if the Key sent in the POST method is stored in DB or not. If that key isn't store than I need to check the number of his keys. If it's than X I'll ban him otherwise i add the new keys in the DB. I'm new with PHP and MYSQL. I wrote this code and I would know if I can improve it. <?php $user = POST METHOD $licenseID = POST METHOD $resultLic= mysql_query("SELECT id , idUser , idLicense FROM license WHERE idUser = '$user'") or die(mysql_error()); $resultNumber = mysql_num_rows($resultLic); $keyFound = '0'; // If keyfound is 1 the key is stored in DB while ($rows = mysql_fetch_array($resultLic,MYSQL_BOTH)) { //this loop check if the $licenseID is stored in DB or not for($i=0; $i< $resultNumber ; i++) { if($rows['idLicense'] === $licenseID) { //Just for the debug echo("License Found"); $keyFound = '1'; break; } //If key isn't in DB and there are less than 3 keys the new key will be store in DB if($keyfound == '0' && $resultNumber < 3) { mysql_query( Update users set ...Store $licenseID in Table) } // Else mean that the user want user another generated key (from the client) in the DB and i will be ban (It's wrote in TOS terms that they cant use the software on more than 3 different station) else { mysql_query( update users set ban ='1'.....etc ); } } ?> I know that this code seems really bad so i would know how i can improve it. Someone Could give me any advice? I choose to have 2 tables: users where all information about the users is, with fields id, username, password and another table license with fields id, idUsername, idLicense (the last one store license that the software generate)

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  • Slick2D - Entities and rendering

    - by Zarkopafilis
    I have been trying to create my very first game for quite a while, followed some tutorials and stuff, but I am stuck at creating my entity system. I have made a class that extends the Entity class and here it is: public class Lazer extends Entity{//Just say that it is some sort of bullet private Play p;//Play class(State) private float x; private float y; private int direction; public Lazer(Play p, float x , float y, int direction){ this.p = p; this.x = x; this.y = y; this.direction = direction; p.ent.add(this); } public int getDirection(){ return direction; //this one specifies what value will be increased (x/y) at update } public float getX(){ return x; } public float getY(){ return y; } public void setY(float y){ this.y = y; } public void setX(float x){ this.x = x; } } The class seems pretty good , after speding some hours googling what would be the right thing. Now, on my Play class. I cant figure out how to draw them. (I have added them to an arraylist) On the update method , I update the lazers based on their direction: public void moveLazers(int delta){ for(int i=0;i<ent.size();i++){ Lazer l = ent.get(i); if(l.getDirection() == 1){ l.setX(l.getX() + delta * .1f); }else if(l.getDirection() == 2){ l.setX(l.getX() - delta * .1f); }else if(l.getDirection() == 3){ l.setY(l.getY() + delta * .1f); }else if(l.getDirection() == 4){ l.setY(l.getY() - delta * .1f); } } } Now , I am stuck at the render method. Anyway , is this the correct way of doing this or do I need to change stuff? Also I need to know if collision detection needs to be in the update method. Thanks in advance ~ Teo Ntakouris

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  • Xna Equivalent of Viewport.Unproject in a draw call as a matrix transformation

    - by Nick Crowther
    I am making a 2D sidescroller and I would like to draw my sprite to world space instead of client space so I do not have to lock it to the center of the screen and when the camera stops the sprite will walk off screen instead of being stuck at the center. In order to do this I wanted to make a transformation matrix that goes in my draw call. I have seen something like this: http://stackoverflow.com/questions/3570192/xna-viewport-projection-and-spritebatch I have seen Matrix.CreateOrthographic() used to go from Worldspace to client space but, how would I go about using it to go from clientspace to worldspace? I was going to try putting my returns from the viewport.unproject method I have into a scale matrix such as: blah = Matrix.CreateScale(unproject.X,unproject.Y,0); however, that doesn't seem to work correctly. Here is what I'm calling in my draw method(where X is the coordinate my camera should follow): Vector3 test = screentoworld(X, graphics); var clienttoworld = Matrix.CreateScale(test.X,test.Y, 0); animationPlayer.Draw(theSpriteBatch, new Vector2(X.X,X.Y),false,false,0,Color.White,new Vector2(1,1),clienttoworld); Here is my code in my unproject method: Vector3 screentoworld(Vector2 some, GraphicsDevice graphics): Vector2 Position =(some.X,some.Y); var project = Matrix.CreateOrthographic(5*graphicsdevice.Viewport.Width, graphicsdevice.Viewport.Height, 0, 1); var viewMatrix = Matrix.CreateLookAt( new Vector3(0, 0, -4.3f), new Vector3(X.X,X.Y,0), Vector3.Up); //I have also tried substituting (cam.Position.X,cam.Position.Y,0) in for the (0,0,-4.3f) Vector3 nearSource = new Vector3(Position, 0f); Vector3 nearPoint = graphicsdevice.Viewport.Unproject(nearSource, project, viewMatrix, Matrix.Identity); return nearPoint;

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  • All chromium extensions throw errors since update to 13.10

    - by hugo der hungrige
    Since updating to 13.10 all chromium extensions generate errors: chrome.extension is not available: 'extension' is not allowed for specified context type content script, extension page, web page, etc.). [VM] binding (56):427 Uncaught TypeError: Cannot call method 'sendRequest' of undefined include.preload.js:105 Uncaught TypeError: Cannot read property 'onRequest' of undefined include.postload.js:473 GET http://edge.quantserve.com/quant.js superuser.com/:2047 GET http://www.google-analytics.com/__utm.gif?utmwv=5.4.5&utms=2&utmn=590704726…n%3D(organic)%7Cutmcmd%3Dorganic%7Cutmctr%3D(not%2520provided)%3B&utmu=qQ~ ga.js:61 chrome.extension is not available: 'extension' is not allowed for specified context type content script, extension page, web page, etc.). [VM] binding (56):427 Uncaught TypeError: Cannot read property 'onRequest' of undefined content.js:233 chrome.extension is not available: 'extension' is not allowed for specified context type content script, extension page, web page, etc.). [VM] binding (56):427 Uncaught TypeError: Cannot read property 'onRequest' of undefined injected.js:169 chrome.extension is not available: 'extension' is not allowed for specified context type content script, extension page, web page, etc.). [VM] binding (56):427 Uncaught TypeError: Cannot call method 'getURL' of undefined content_js_min.js:5 GET http://engine.adzerk.net/z/8476/adzerk2_2_17_47 superuser.com/:1719 Uncaught TypeError: Cannot call method 'sendRequest' of undefined How to fix this?

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  • How to bind std::map to Lua with LuaBind

    - by MahanGM
    Is this possible in lua to achieve? player.scripts["movement"].properties["stat"] = "stand" print (player.scripts["movement"].properties["stat"]) I've done getter method in c++ with this approach: luabind::object FakeScript::getProp() { luabind::object obj = luabind::newtable(L); for(auto i = this->properties.begin(); i != this->properties.end(); i++) { obj[i->first] = i->second; } return obj; } But I'm stuck with setter. The first line in lua code which I'm trying to set value "stand" for key "stat" is not going to work and it keep redirecting me to the getter method. Setter method only works when I drop ["stat"] from properties. I can do something like this for setter in my script: player.scripts["movement"].properties = {stat = "stand"} But this isn't what I want because I have to go through my real keys in c++ to determine which key is placed in setter argument table value. This is my map in class: std::map<std::string, std::string> properties;

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  • How to fetch only the sprites in the player's range of motion for collision testing? (2D, axis aligned sprites)

    - by Twodordan
    I am working on a 2D sprite game for educational purposes. (In case you want to know, it uses WebGl and Javascript) I've implemented movement using the Euler method (and delta time) to keep things simple. Now I'm trying to tackle collisions. The way I wrote things, my game only has rectangular sprites (axis aligned, never rotated) of various/variable sizes. So I need to figure out what I hit and which side of the target sprite I hit (and I'm probably going to use these intersection tests). The old fashioned method seems to be to use tile based grids, to target only a few tiles at a time, but that sounds silly and impractical for my game. (Splitting the whole level into blocks, having each sprite's bounding box fit multiple blocks I might abide. But if the sprites change size and move around, you have to keep changing which tiles they belong to, every frame, it doesn't sound right.) In Flash you can test collision under one point, but it's not efficient to iterate through all the elements on stage each frame. (hence why people use the tile method). Bottom line is, I'm trying to figure out how to test only the elements within the player's range of motion. (I know how to get the range of motion, I have a good idea of how to write a collisionCheck(playerSprite, targetSprite) function. But how do I know which sprites are currently in the player's vicinity to fetch only them?) Please discuss. Cheers!

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  • fglrx: No matching Device section for instance... found how to fix it?

    - by Lejo
    I have HD 4850 card, Ubuntu 12.10 and installed legacy drivers using makson96 ppa. The issue is, that FGLRX can not detect my device and loads vesa bios. I had the same problem on ubuntu 11.10, 12.04 versions. I want to manually help fglrx find a matching device to load as it shoudld do. It is interesting, why does fglrx search for a device in a PCI:0@1:0:1 Bus? in xorg.cof different bus is indicated: Section "Device" Identifier "aticonfig-Device[0]-0" Driver "fglrx" BusID "PCI:1:0:0" EndSection fglrxinfo display: :0.0 screen: 0 OpenGL vendor string: Advanced Micro Devices, Inc. OpenGL renderer string: ATI Radeon HD 4800 Series OpenGL version string: 3.3.11653 Compatibility Profile Context Here is a part of my xorg log: [ 3.846] (II) VESA: driver for VESA chipsets: vesa [ 3.846] (II) FBDEV: driver for framebuffer: fbdev [ 3.846] (++) using VT number 7 [ 3.846] (WW) Falling back to old probe method for fglrx [ 3.883] (II) Loading PCS database from /etc/ati/amdpcsdb [ 3.883] (--) Assigning device section with no busID to primary device [ 3.883] (--) Chipset Supported AMD Graphics Processor (0x9442) found [ 3.884] (WW) fglrx: No matching Device section for instance (BusID PCI:0@1:0:1) found [ 3.884] (II) AMD Video driver is running on a device belonging to a group targeted for this release [ 3.884] (II) AMD Video driver is signed [ 3.884] (II) fglrx(0): pEnt->device->identifier=0xb7791d8f [ 3.884] (WW) Falling back to old probe method for vesa [ 3.884] (WW) Falling back to old probe method for fbdev from lispci i foud out finally, that my video card is in 01:00.0 slot. logically, if fglrx searches for a vdeo card device in a wrong place, it will not find it. 01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI RV770 [Radeon HD 4850] Thanks in advance.

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  • Integration error in high velocity

    - by Elektito
    I've implemented a simple simulation of two planets (simple 2D disks really) in which the only force is gravity and there is also collision detection/response (collisions are completely elastic). I can launch one planet into orbit of the other just fine. The collision detection code though does not work so well. I noticed that when one planet hits the other in a free fall it speeds backward and goes much higher than its original position. Some poking around convinced me that the simplistic Euler integration is causing the error. Consider this case. One object has a mass of 1kg and the other has a mass equal to earth. Say the object is 10 meters above ground. Assume that our dt (delta t) is 1 second. The object goes to the height of 9 meters at the end of the first iteration, 7 at the end of the second, 4 at the end of the third and 0 at the end of the fourth iteration. At this points it hits the ground and bounces back with the speed of 10 meters per second. The problem is with dt=1, on the first iteration it bounces back to a height of 10. It takes several more steps to make the object change its course. So my question is, what integration method can I use which fixes this problem. Should I split dt to smaller pieces when velocity is high? Or should I use another method altogether? What method do you suggest? EDIT: You can see the source code here at github:https://github.com/elektito/diskworld/

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  • XNA CustomModelAnimationSample problem

    - by Mentoliptus
    I downloaded the official tutorial from:CustomModelAnimationSample It works fine but when I try to replicate it in my project, it fails to load the Tag property in my model. Is found that the probelm is in the line: skinnedModel = Content.Load<Model>("DudeWalk"); This line loads the model from the DudeWalk.fbx file and with the custom SkinnedModelProcessor. It loads the animations data in the model. After the line the Tag property is full. I stepped into the method and it went to the custom ModelData class. I copied everything from the projects CustomModelAnimationWindows and CustomModelAnimationPipeline to my solution and set all the references. I tried the same line of code and couldn't step in the method. It called the default method or model constructor and after the line the model's Tag propetry was null. I have to load the model through my custom SkinnedModelProcessor class, but how I tell the game to use this class? In the tutroail CustomModelClass the line is changed to: model = Content.Load<CustomModel>("tank"); So I assumed that I have to set the generic type to a custom model class, but the first example works without it. If anyone has some useful advice or some other helpful link, I'll be happy to try it.

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  • CheckMemoryAllocationGame Sample

    - by Michael B. McLaughlin
    Many times I’ve found myself wondering how much GC memory some operation allocates. This is primarily in the context of XNA games due to the desire to avoid generating garbage and thus triggering a GC collection. Many times I’ve written simple programs to check allocations. I did it again recently. It occurred to me that many XNA developers find themselves asking this question from time to time. So I cleaned up my sample and published it on my website. Feel free to download it and put it to use. It’s rather thoroughly commented. The location where you insert the code you wish to check is in the Update method found in Game1.cs. The default that I put in is a line of code that generates a new Guid using Guid.NewGuid (which, if you’re curious, does not create any heap allocations). Read all of the comments in the Update method (at the very least) to make sure that your code is measured properly. It’s important to make sure that you meaningfully reference any thing you create after the second call to get the memory or else (in Release configuration at least) you will likely get incorrect results. Anyway, it should make sense when you read the comments and if not, feel free to post a comment here or ask me on Twitter. You can find my utilities and code samples page here: http://www.bobtacoindustries.com/developers/utils/Default.aspx To download CheckMemoryAllocationGame’s source code directly: http://www.bobtacoindustries.com/developers/utils/CheckMemoryAllocationGame.zip (If you’re looking to do this outside of the context of an XNA game, the measurement code in the Update method can easily be adapted into, e.g., a C# Windows Console application. In the past I mostly did that, actually. But I didn’t feel like adding references to all the XNA assemblies this time and… anyway, if you want you can easily convert it to a console application. If there’s any demand for it, I’ll do it myself and update this post when I get a chance.)

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  • What is the difference between Callback<T> and Java 8's Supplier<T>?

    - by Dan Pantry
    I've been switching over to Java from C# after some recommendations from some over at CodeReview. So, when I was looking into LWJGL, one thing I remembered was that every call to Display must be executed on the same thread that the Display.create() method was invoked on. Remembering this, I whipped up a class that looks a bit like this. public class LwjglDisplayWindow implements DisplayWindow { private final static int TargetFramesPerSecond = 60; private final Scheduler _scheduler; public LwjglDisplayWindow(Scheduler displayScheduler, DisplayMode displayMode) throws LWJGLException { _scheduler = displayScheduler; Display.setDisplayMode(displayMode); Display.create(); } public void dispose() { Display.destroy(); } @Override public int getTargetFramesPerSecond() { return TargetFramesPerSecond; } @Override public Future<Boolean> isClosed() { return _scheduler.schedule(() -> Display.isCloseRequested()); } } While writing this class you'll notice that I created a method called isClosed() that returns a Future<Boolean>. This dispatches a function to my Scheduler interface (which is nothing more than a wrapper around an ScheduledExecutorService. While writing the schedule method on the Scheduler I noticed that I could either use a Supplier<T> argument or a Callable<T> argument to represent the function that is passed in. ScheduledExecutorService didn't contain an override for Supplier<T> but I noticed that the lambda expression () -> Display.isCloseRequested() is actually type compatible with both Callable<bool> and Supplier<bool>. My question is, is there a difference between those two, semantically or otherwise - and if so, what is it, so I can adhere to it?

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  • (Abstract) Game engine design

    - by lukeluke
    I am writing a simple 2D game (for mobile platforms) for the first time. From an abstract point of view, i have the main player controlled by the human, the enemies, elments that will interact with the main player, other living elements that will be controlled by a simple AI (both enemies and non-enemies). The human player will be totally controlled by the player, the other actors will be controlled by AI. So i have a class CActor and a class CActorLogic to start with. I would define a CActor subclass CHero (the main player controlled with some input device). This class will probably implement some type of listener, in order to capture input events. The other players controlled by the AI will be probably a specific subclass of CActor (a subclass per-type, obviously). This seems to be reasonable. The CActor class should have a reference to a method of CActorLogic, that we will call something like CActorLogic::Advance() or similar. Actors should have a visual representation. I would introduce a CActorRepresentation class, with a method like Render() that will draw the actor (that is, the right frame of the right animation). Where to change the animation? Well, the actor logic method Advance() should take care of checking collisions and other things. I would like to discuss the design of a game engine (actors, entities, objects, messages, input handling, visualization of object states (that is, rendering, sound output and so on)) but not from a low level point of view, but from an high level point of view, like i have described above. My question is: is there any book/on line resource that will help me organize things (using an object oriented approach)? Thanks

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  • Strategies for managUse of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • Detecting collision between ball (circle) and brick(rectangle)?

    - by James Harrison
    Ok so this is for a small uni project. My lecturer provided me with a framework for a simple brickbreaker game. I am currently trying to overcome to problem of detecting a collision between the two game objects. One object is always the ball and the other objects can either be the bricks or the bat. public Collision hitBy( GameObject obj ) { //obj is the bat or the bricks //the current object is the ball // if ball hits top of object if(topX + width >= obj.topX && topX <= obj.topX + obj.width && topY + height >= obj.topY - 2 && topY + height <= obj.topY){ return Collision.HITY; } //if ball hits left hand side else if(topY + height >= obj.topY && topY <= obj.topY + obj.height && topX + width >= obj.topX -2 && topX + width <= obj.topX){ return Collision.HITX; } else return Collision.NO_HIT; } So far I have a method that is used to detect this collision. The the current obj is a ball and the obj passed into the method is the the bricks. At the moment I have only added statement to check for left and top collisions but do not want to continue as I have a few problems. The ball reacts perfectly if it hits the top of the bricks or bat but when it hits the ball often does not change directing. It seems that it is happening toward the top of the left hand edge but I cannot figure out why. I would like to know if there is another way of approaching this or if people know where I'm going wrong. Lastly the collision.HITX calls another method later on the changes the x direction likewise with y.

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  • Custom field names in Rails error messages

    - by Madhan ayyasamy
    The defaults in Rails with ActiveRecord is beautiful when you are just getting started and are created everything for the first time. But once you get into it and your database schema becomes a little more solidified, the things that would have been easy to do by relying on the conventions of Rails require a little bit more work.In my case, I had a form where there was a database column named “num_guests”, representing the number of guests. When the field fails to pass validation, the error messages is something likeNum guests is not a numberNot quite the text that we want. It would be better if it saidNumber of guests is not a numberAfter doing a little bit of digging, I found the human_attribute_name method. You can override this method in your model class to provide alternative names for fields. To change our error message, I did the followingclass Reservation ... validates_presence_of :num_guests ... HUMAN_ATTRIBUTES = { :num_guests = "Number of guests" } def self.human_attribute_name(attr) HUMAN_ATTRIBUTES[attr.to_sym] || super endendSince Rails 2.2, this method is used to support internationalization (i18n). Looking at it, it reminds me of Java’s Resource Bundles and Spring MVC’s error messages. Messages are defined based off a key and there’s a chain of look ups that get applied to resolve an error’s message.Although, I don’t see myself doing any i18n work in the near-term, it is cool that we have that option now in Rails.

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  • For a Javascript library, what is the best or standard way to support extensibility

    - by Michael Best
    Specifically, I want to support "plugins" that modify the behavior of parts of the library. I couldn't find much information on the web about this subject. But here are my ideas for how a library could be extensible. The library exports an object with both public and "protected" functions. A plugin can replace any of those functions, thus modifying the library's behavior. Advantages of this method are that it's simple and that the plugin's functions can have full access to the library's "protected" functions. Disadvantages are that the library may be harder to maintain with a larger set of exposed functions and it could be hard to debug if multiple plugins are involved (how to know which plugin modified which function?). The library provides an "add plugin" function that accepts an object with a specific interface. Internally, the library will use the plugin instead of it's own code if appropriate. With this method, the internals of the library can be rearranged more freely as long as it still supports the same plugin interface. This could also support having different plugin interfaces to modify different parts of the library. A disadvantage of this method is that the plugins may have to re-implement code that is already part of the library since the library's internal functions are not exported. The library provides a "set implementation" function that accepts an object inherited from a specific base object. The library's public API calls functions in the implementation object for any functionality that can be modified and the base implementation object includes the core functionality, with both external (to the API) and internal functions. A plugin creates a new implementation object, which inherits from the base object and replaces any functions it wants to modify. This combines advantages and disadvantages of both the other methods.

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  • Rails: Law of Demeter Confusion

    - by user2158382
    I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. EDIT I completely understand and agree that this is still a violation and I need to create a method in Wallet called withdraw that handles the payment for me and that I should call that method inside the Customer class. What I don't get is that according to this process, my first example still violates the Law of Demeter because Invoice is still reaching directly into Customer to get the street. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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  • Explicitly pass context object versus injecting with IoC

    - by SonOfPirate
    I have a layered service application where the service layer delegates operations into the domain layer for execution. Many of these operations need to know the context under which they are operation. (The context included the identity of the current user, culture information, etc. received from the caller.) For example, I have an API method that returns a list of announcements. The list is based on the current user's role and each announcement is localized to their culture. The API is a thin-facade that delegates to an Application Service in my domain layer. The Application Service method obviously needs to know the context of the current request/operation as another call to the same API from another user should result in a different list. Within this method, we also have logging that uses some of the context information so we a clear understanding of the context when the operation was performed (this is especially useful if something goes wrong.) While this is a contrived example, in the real world, my Application Services will coordinate operations with many collaborative components, any number of them also needing the context information. My choice is to pass the context to the Application Service which would then pass it with any calls to collaborators or have the IoC container satisfy the dependency the Application Service and any collaborators have on the context. I am wondering if it is considered good/bad, best practices/code smell, etc. if I pass the context object as a parameter to the domain methods or if injecting the context via an IoC container is preferred. (EDIT: I should mention that the context object is instantiated per-request.)

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  • Initializing entities vs having a constructor parameter

    - by Vee
    I'm working on a turn-based tile-based puzzle game, and to create new entities, I use this code: Field.CreateEntity(10, 5, Factory.Player()); This creates a new Player at [10; 5]. I'm using a factory-like class to create entities via composition. This is what the CreateEntity method looks like: public void CreateEntity(int mX, int mY, Entity mEntity) { mEntity.Field = this; TileManager.AddEntity(mEntity, true); GetTile(mX, mY).AddEntity(mEntity); mEntity.Initialize(); InvokeOnEntityCreated(mEntity); } Since many of the components (and also logic) of the entities require to know what the tile they're in is, or what the field they belong to is, I need to have mEntity.Initialize(); to know when the entity knows its own field and tile. The Initialize(); method contains a call to an event handler, so that I can do stuff like this in the factory class: result.OnInitialize += () => result.AddTags(TDLibConstants.GroundWalkableTag, TDLibConstants.TrapdoorTag); result.OnInitialize += () => result.AddComponents(new RenderComponent(), new ElementComponent(), new DirectionComponent()); This works so far, but it is not elegant and it's very open to bugs. I'm also using the same idea with components: they have a parameterless constructor, and when you call the AddComponent(mComponent); method in an entity, it is the entity's job to set the component's entity to itself. The alternative would be having a Field, int, int parameters in the factory class, to do stuff like: new Entity(Field, 10, 5); But I also don't like the fact that I have to create new entities like this. I would prefer creating entities via the Field object itself. How can I make entity/component creation more elegant and less prone to bugs?

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  • Reaching Intermediate Programming Status

    - by George Stocker
    I am a software engineer that's had positions programming in VBA (though I dare not consider that 'real' experience, as it was trial and error!), Perl w/ CGI, C#, and ASP.NET. The latter two are post-undergraduate, with my entrance into the 'real world'. I'm 2 years out of college, and have had 5 years of experience (total) across the languages I've mentioned. However, when it comes to my resume, I can only put 2 years down for C#, and less than a year down for ASP.NET. I feel like I know C#, but I still have to spend time going 'What does this method do?', whereas some of the more senior level engineers can immediately say, "Oh, Method X does this, without ever having looked at that method before." So I know empirically that there's a gulf there, but I'm not exactly sure how to bridge it. I've started programming in Project Euler, and I picked up a book on design patterns, but I still feel like I spend each day treading water, instead of moving forward. That isn't to say that I don't feel like I've made progress, it just means that as far as I come each day, I still see the mountain top way off in the distance. My question is this: How did you overcome this plateau? How long did it take you? What methods can you suggest to assist me in this? I've read through Code Complete, The Mythical Man Month, and CLR via C#, 2nd edition -- my question is: What do I do now? Edit: I just found this question on projects for an intermediate level programmer. I think it adds to the discussion (though it does not supplant my question). As such, I'm adding it to the question as a "For More Information".

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  • Should I modify an entity with many parameters or with the entity itself?

    - by Saeed Neamati
    We have a SOA-based system. The service methods are like: UpdateEntity(Entity entity) For small entities, it's all fine. However, when entities get bigger and bigger, to update one property we should follow this pattern in UI: Get parameters from UI (user) Create an instance of the Entity, using those parameters Get the entity from service Write code to fill the unchanged properties Give the result entity to the service Another option that I've experienced in previous experiences is to create semantic update methods for each update scenario. In other words instead of having one global all-encompasing update method, we had many ad-hoc parametric methods. For example, for the User entity, instead of having UpdateUser (User user) method, we had these methods: ChangeUserPassword(int userId, string newPassword) AddEmailToUserAccount(int userId, string email) ChangeProfilePicture(int userId, Image image) ... Now, I don't know which method is truly better, and for each approach, we encounter problems. I mean, I'm going to design the infrastructure for a new system, and I don't have enough reasons to pick any of these approaches. I couldn't find good resources on the Internet, because of the lack of keywords I could provide. What approach is better? What pitfalls each has? What benefits can we get from each one?

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