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• How to install chrome autosave extension?

  - by Oguz Can Sertel

  I would like to install chrome autosave plugin on ubuntu. when I try to install it with these steps https://github.com/NV/chrome-devtools-autosave-server , I got some errors... there was not installed node and npm out of box on ubuntu 12.10. So I installed npm and node with these commands. sudo apt-get install npm sudo apt-get install node and I tried to install autosave here is the output: sudo npm install -g autosave npm http GET https://registry.npmjs.org/autosave npm http 304 https://registry.npmjs.org/autosave npm http GET https://registry.npmjs.org/commander npm http 304 https://registry.npmjs.org/commander /usr/local/bin/autosave -> /usr/local/lib/node_modules/autosave/bin/autosave > [email protected] install /usr/local/lib/node_modules/autosave > node ./scripts/install.js npm ERR! error installing [email protected] npm WARN This failure might be due to the use of legacy binary "node" npm WARN For further explanations, please read npm WARN /usr/share/doc/nodejs/README.Debian npm WARN npm ERR! [email protected] install: `node ./scripts/install.js` npm ERR! `sh "-c" "node ./scripts/install.js"` failed with 1 npm ERR! npm ERR! Failed at the [email protected] install script. npm ERR! This is most likely a problem with the autosave package, npm ERR! not with npm itself. npm ERR! Tell the author that this fails on your system: npm ERR! node ./scripts/install.js npm ERR! You can get their info via: npm ERR! npm owner ls autosave npm ERR! There is likely additional logging output above. npm ERR! npm ERR! System Linux 3.5.0-17-generic npm ERR! command "/usr/bin/nodejs" "/usr/bin/npm" "install" "-g" "autosave" npm ERR! cwd /home/naczu npm ERR! node -v v0.6.19 npm ERR! npm -v 1.1.4 npm ERR! code ELIFECYCLE npm ERR! message [email protected] install: `node ./scripts/install.js` npm ERR! message `sh "-c" "node ./scripts/install.js"` failed with 1 npm ERR! errno {} npm ERR! npm ERR! Additional logging details can be found in: npm ERR! /home/naczu/npm-debug.log npm not ok and here is README.debian nodejs for Debian ================= packaged modules ---------------- The global search path for modules is /usr/lib/nodejs Future packages of node modules will use that directory, so it should be used wisely. user modules ------------ Node looks for modules in ./node_modules directory first; please read node#modules documentation carefully for more information. Node does not look for modules in /usr/local/lib/node_modules, where npm put them. Please read npm-link(1) of npm package, to understand how to properly use npm-installed modules in a project. Note that require.paths is not supported in future node versions. See also node(1) for more information about NODE_PATH. nodejs command -------------- The upstream name for the Node.js interpreter command is "node". In Debian the interpreter command has been changed to "nodejs". This was done to prevent a namespace collision: other commands use the same name in their upstreams, such as ax25-node from the "node" package. Scripts calling Node.js as a shell command must be changed to instead use the "nodejs" command.

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• Best depth sorting method for a Top Down 2D game using a 3D physics engine

  - by Alic44

  I've spent many days googling this and still have issues with my game engine I'd like to ask about, which I haven't seen addressed before. I think the problem is that my game is an unusual combination of a completely 2D graphical approach using XNA's SpriteBatch, and a completely 3D engine (the amazing BEPU physics engine) with rotation mostly disabled. In essence, my question is similar to this one (the part about "faux 3D"), but the difference is that in my game, the player as well as every other creature is represented by 3D objects, and they can all jump, pick up other objects, and throw them around. What this means is that sorting by one value, such as a Z position (how far north/south a character is on the screen) won't work, because as soon as a smaller creature jumps on top of a larger creature, or a box, and walks backwards, the moment its z value is less than that other creature, it will appear to be behind the object it is actually standing on. I actually originally solved this problem by splitting every object in the game into physics boxes which MUST have a Y height equal to their Z depth. I then based the depth sorting value on the object's y position (how high it is off the ground) PLUS its z position (how far north or south it is on the screen). The problem with this approach is that it requires all moving objects in the game to be split graphically into chunks which match up with a physical box which has its y dimension equal to its z dimension. Which is stupid. So, I got inspired last night to rewrite with a fresh approach. My new method is a little more complex, but I think a little more sane: every object which needs to be sorted by depth in the game exposes the interface IDepthDrawable and is added to a list owned by the DepthDrawer object. IDepthDrawable contains: public interface IDepthDrawable { Rectangle Bounds { get; } //possibly change this to a class if struct copying of the xna Rectangle type becomes an issue DepthDrawShape DepthShape { get; } void Draw(SpriteBatch spriteBatch); } The Bounds Rectangle of each IDepthDrawable object represents the 2D Axis-Aligned Bounding Box it will take up when drawn to the screen. Anything that doesn't intersect the screen will be culled at this stage and the remaining on-screen IDepthDrawables will be Bounds tested for intersections with each other. This is where I get a little less sure of what I'm doing. Each group of collisions will be added to a list or other collection, and each list will sort itself based on its DepthShape property, which will have access to the object-to-be-drawn's physics information. For starting out, lets assume everything in the game is an axis aligned 3D Box shape. Boxes are pretty easy to sort. Something like: if (depthShape1.Back > depthShape2.Front) //if depthShape1 is in front of depthShape2. //depthShape1 goes on top. else if (depthShape1.Bottom > depthShape2.Top) //if depthShape1 is above depthShape2. //depthShape1 goes on top. //if neither of these are true, depthShape2 must be in front or above. So, by sorting draw order by several different factors from the physics engine, I believe I can get a really correct draw order. My question is, is this a good way of going about this, or is there some tried and true, tested way which is completely different and has somehow completely eluded me on the internets? And, if this does seem like a good way to remake my draw order sorting, what's the right sorting algorithm for reordering the Bounds Rectangle collision lists, and how do you deal with a Bounds Rectangle colliding with two different object which don't collide with eachother. I know these are solved problems, but I've only been programming for a year so any specific input here will be greatly appreciated. Thanks for reading this far, ye who made it -- sorry it was so long!

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• Fixing some Visual Studio RC install issues

  - by terje

  The Visual Studio RC has shown some install issues in some cases, particularly for those who upgrades from VS 11 Beta.  I have listed the fixes known now below, and will update if there are more issues.  Note that a repair will not fix the issue, and a Windows restore and subsequent reinstall may not fix it either.  The system seems to remember too much. That was the case for me, at least.  The fixes below however, cures these issues. 1. The Team Explorer Build node doesn’t work You get an error saying System.TypeLoadException like this: To solve this do as follows: 1. Open a command prompt as administrator 2. Go to your program files directory for VS 2012 and down to  the extension folder like:   C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer 3. Run “gacutil –if Microsoft.TeamFoundation.Build.Controls.dll     2. The SQL Editor gives loading error When you start up VS 2012 RC you get a loading error message.  The same happens if you try to go from the menu to  SQL/Transact-SQL Editor/New Query.    To solve this do as follows: 1. Open Control Panel/Programs and Features 2. Locate the “Microsoft SQL Server 2012 Data-Tier App Framework     (Note , you might find up to 4 such instances) The ones with version numbers ending in 55 is from the SQL 2012 RC, the ones ending in 60 is from the SQL 2012 RTM.  There are two of each, one for x32 and one for x64.  Which is which no one knows. 3. Right click each of them, and select Repair. (It would be nice if someone with this issue tries only the latest RTM ones, and see if that clears the error, and comment back to this post. I am out of non-functioning VS’s )   3.  Errors referring to some extension You get errors referring to some extension that can’t be loaded, or can’t be found.  Check the activity log (see below), and verify there.  If you see yellow collision warnings there, the fix here should solve those too. To solve these:    1. Open a Visual Studio 2012 command prompt 2.  Run:   devenv /resetsettings     How to check for errors using the log Do as follows to get to the activity log for Visual studio 2012 RC 1. Open a Visual Studio 2012 command prompt 2. Run:   devenv /log This starts up Visual Studio.  3. Go to %appdata%/Microsoft\VisualStudio\11.0 4. Double click the file named ActivityLog.xml.  It will start up in your browser, and be formatted using the xslt in the same directory. 5.  Look for items marked in red.  Example for Issue 1 :

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• How do I cap rendering of tiles in a 2D game with SDL?

  - by farmdve

  I have some boilerplate code working, I basically have a tile based map composed of just 3 colors, and some walls and render with SDL. The tiles are in a bmp file, but each tile inside it corresponds to an internal number of the type of tile(color, or wall). I have pretty basic collision detection and it works, I can also detetc continuous presses, which allows me to move pretty much anywhere I want. I also have a moving camera, which follows the object. The problem is that, the tile based map is bigger than the resolution, thus not all of the map can be displayed on the screen, but it's still rendered. I would like to cap it, but since this is new to me, I pretty much have no idea. Although I cannot post all the code, as even though I am a newbie and the code pretty basic, it's already quite a few lines, I can post what I tried to do void set_camera() { //Center the camera over the dot camera.x = ( player.box.x + DOT_WIDTH / 2 ) - SCREEN_WIDTH / 2; camera.y = ( player.box.y + DOT_HEIGHT / 2 ) - SCREEN_HEIGHT / 2; //Keep the camera in bounds. if(camera.x < 0 ) { camera.x = 0; } if(camera.y < 0 ) { camera.y = 0; } if(camera.x > LEVEL_WIDTH - camera.w ) { camera.x = LEVEL_WIDTH - camera.w; } if(camera.y > LEVEL_HEIGHT - camera.h ) { camera.y = LEVEL_HEIGHT - camera.h; } } set_camera() is the function which calculates the camera position based on the player's positions. I won't pretend I know much about it. Rectangle box = {0,0,0,0}; for(int t = 0; t < TOTAL_TILES; t++) { if(box.x < (camera.x - TILE_WIDTH) || box.y > (camera.y - TILE_HEIGHT)) apply_surface(box.x - camera.x, box.y - camera.y, surface, screen, &clips[tiles[t]]); box.x += TILE_WIDTH; //If we've gone too far if(box.x >= LEVEL_WIDTH) { //Move back box.x = 0; //Move to the next row box.y += TILE_HEIGHT; } } This is basically my render code. The for loop loops over 192 tiles stored in an int array, each with their own unique value describing the tile type(wall or one of three possible colored tiles). box is an SDL_Rect containing the current position of the tile, which is calculated on render. TILE_HEIGHT and TILE_WIDTH are of value 80. So the cap is determined by if(box.x < (camera.x - TILE_WIDTH) || box.y > (camera.y - TILE_HEIGHT)) However, this is just me playing with the values and see what doesn't break it. I pretty much have no idea how to calculate it. My screen resolution is 1024/768, and the tile map is of size 1280/960.

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• Making AI jump on a spot effectively

  - by Pasquale Sada

  How to calculate, in 3D environment, the closest point, from which an AI character can jump onto a platform? Setup I have an initial velocity V(Vx,Vy,VZ) and a spot where the character stands still at S(Sx,Sy,Sz). What I'm trying to achieve is a successful jump on a spot E(Ex,Ey,Ez) where you have clicked on(only lower or higher spot, because I've in place a simple steering behavior for even terrains). There are no obstacles around. I've implemented a formula that can make him jump in a precise way on a spot but you need to declare an angle: the problem arise when the selected spot is straight above your head. It' pretty lame that the char hang there and can reach a thing that is 1cm above is head. I'll share the code I'm using: Vector3 dir = target - transform.position; // get target direction float h = dir.y; // get height difference dir.y = 0; // retain only the horizontal direction float dist = dir.magnitude ; // get horizontal distance float a = angle * Mathf.Deg2Rad; // convert angle to radians dir.y = dist * Mathf.Tan(a); // set dir to the elevation angle dist += h / Mathf.Tan(a); // correct for small height differences // calculate the velocity magnitude float vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 *a)); return vel * dir.normalized; Ended up using the lowest angle (20 degree) and checking for collision on the trajectory. If found any increase the angle. Here some code (to improve the code maybe must stop the check at the highest point of the curve): Vector3 BallisticVel(Vector3 target, float angle) { Vector3 dir = target - transform.position; // get target direction float h = dir.y; // get height difference dir.y = 0; // retain only the horizontal direction float dist = dir.magnitude ; // get horizontal distance float a = angle * Mathf.Deg2Rad; // convert angle to radians dir.y = dist * Mathf.Tan(a); // set dir to the elevation angle dist += h / Mathf.Tan(a); // correct for small height differences // calculate the velocity magnitude float vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 * a)); return vel * dir.normalized; } Vector3 TrajectoryPoint(Vector3 startingPosition, Vector3 startingVelocity, float n ) { float t = 1/60 ; // seconds per time step Vector3 stepVelocity = t * startingVelocity; // m/s Vector3 stepGravity = t * t * Physics.gravity; // m/s/s return startingPosition + n * stepVelocity + 0.5f * (n*n+n) * stepGravity; } bool CheckTrajectory(Vector3 startingPosition,Vector3 target, float angle_jump) { Debug.Log("checking"); if(angle_jump < 80f) { Debug.Log("if"); Vector3 startingVelocity = BallisticVel(target, angle_jump); for (int i = 0; i < 180; i++) { //Debug.Log(i); Vector3 trajectoryPosition = TrajectoryPoint( startingPosition, startingVelocity, i ); if(Physics.Raycast(trajectoryPosition,Vector3.forward,safeDistance)) { angle_jump += 10; break; // restart loop with the new angle } else continue; } return true; JumpVelocity = BallisticVel(target, angle_jump); } return false; }

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• What common interface would be appropriate for these game object classes?

  - by Jefffrey

  Question A component based system's goal is to solve the problems that derives from inheritance: for example the fact that some parts of the code (that are called components) are reused by very different classes that, hypothetically, would lie in a very different branch of the inheritance tree. That's a very nice concept, but I've found out that CBS is often hard to accomplish without using ugly hacks. Implementations of this system are often far from clean. But I don't want to discuss this any further. My question is: how can I solve the same problems a CBS try to solve with a very clean interface? (possibly with examples, there are a lot of abstract talks about the "perfect" design already). Context Here's an example I was going for before realizing I was just reinventing inheritance again: class Human { public: Position position; Movement movement; Sprite sprite; // other human specific components }; class Zombie { Position position; Movement movement; Sprite sprite; // other zombie specific components }; After writing that I realized I needed an interface, otherwise I would have needed N containers for N different types of objects (or to use boost::variant to gather them all together). So I've thought of polymorphism (move what systems do in a CBS design into class specific functions): class Entity { public: virtual void on_event(Event) {} // not pure virtual on purpose virtual void on_update(World) {} virtual void on_draw(Window) {} }; class Human : public Entity { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; class Zombie : public Entity { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; Which was nice, except for the fact that now the outside world would not even be able to know where a Human is positioned (it does not have access to its position member). That would be useful to track the player position for collision detection or if on_update the Zombie would want to track down its nearest human to move towards him. So I added const Position& get_position() const; to both the Zombie and Human classes. And then I realized that both functionality were shared, so it should have gone to the common base class: Entity. Do you notice anything? Yes, with that methodology I would have a god Entity class full of common functionality (which is the thing I was trying to avoid in the first place). Meaning of "hacks" in the implementation I'm referring to I'm talking about the implementations that defines Entities as simple IDs to which components are dynamically attached. Their implementation can vary from C-stylish: int last_id; Position* positions[MAX_ENTITIES]; Movement* movements[MAX_ENTITIES]; Where positions[i], movements[i], component[i], ... make up the entity. Or to more C++-style: int last_id; std::map<int, Position> positions; std::map<int, Movement> movements; From which systems can detect if an entity/id can have attached components.

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• Improving the efficiency of frustum culling

  - by DeadMG

  I've got some code which performs frustum culling. However, this defines the "frustum" way too broadly- when I have ~10 objects on screen, the code returns 42 objects to be rendered. I've tried taking "slices" through the frustum to attempt to increase the accuracy of the technique, but it doesn't seem to have made much impact. I also significantly reduced the far plane, so that the objects are barely at the edge. Here's my code (where size is the size in screen space- the resolution of the client area of the window I'm rendering into). Any suggestions? auto&& size = GetDimensions(); D3DVIEWPORT9 vp = { 0, 0, size.x, size.y, 0, 1 }; D3DCALL(device->SetViewport(&vp)); static const int slices = 10; std::vector<Object*> result; for(int i = 0; i < slices; i++) { D3DXVECTOR3 WorldSpaceFrustrumPoints[8] = { D3DXVECTOR3(0, size.y, static_cast<float>(i) / slices), D3DXVECTOR3(size.x, 0, static_cast<float>(i) / slices), D3DXVECTOR3(size.x, size.y, static_cast<float>(i) / slices), D3DXVECTOR3(0, 0, static_cast<float>(i) / slices), D3DXVECTOR3(0, 0, static_cast<float>(i + 1) / slices), D3DXVECTOR3(size.x, 0, static_cast<float>(i + 1) / slices), D3DXVECTOR3(size.x, size.y, static_cast<float>(i + 1) / slices), D3DXVECTOR3(0, size.y, static_cast<float>(i + 1) / slices) }; D3DXMATRIXA16 Identity; D3DXMatrixIdentity(&Identity); D3DXVec3UnprojectArray( WorldSpaceFrustrumPoints, sizeof(D3DXVECTOR3), WorldSpaceFrustrumPoints, sizeof(D3DXVECTOR3), &vp, &Projection, &View, &Identity, 8 ); Math::AABB Frustrum; auto world_begin = std::begin(WorldSpaceFrustrumPoints); auto world_end = std::end(WorldSpaceFrustrumPoints); auto world_initial = WorldSpaceFrustrumPoints[0]; Frustrum.BottomLeftClosest.x = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.x < rhs.x ? lhs : rhs; }).x; Frustrum.BottomLeftClosest.y = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.y < rhs.y ? lhs : rhs; }).y; Frustrum.BottomLeftClosest.z = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.z < rhs.z ? lhs : rhs; }).z; Frustrum.TopRightFurthest.x = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.x > rhs.x ? lhs : rhs; }).x; Frustrum.TopRightFurthest.y = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.y > rhs.y ? lhs : rhs; }).y; Frustrum.TopRightFurthest.z = std::accumulate(world_begin, world_end, world_initial, [](D3DXVECTOR3 lhs, D3DXVECTOR3 rhs) { return lhs.z > rhs.z ? lhs : rhs; }).z; auto slices_result = ObjectTree.collision(Frustrum); result.insert(result.end(), slices_result.begin(), slices_result.end()); } return result;

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• JSF 2/Primefaces p:ajax not updating panel after onchange event is fired

  - by Ravi S

  I am really stuck with this for the last 2 days and am struggling to understand how Primefaces updates UI components on the client based on their ID. I have a h:selectOneMenu with a count for the number of panels to be displayed. Each p:panel will contain a panelGrid with numerous form elements. The onchange event on the drop down is fired and I can see the count in the Managed Bean. I do not see panels increasing dynamically on the client side though.i think something is wrong with my p:ajax params, but I don;t fully understand how it works. here is the relevant code: <h:selectOneMenu id="numapps" value="#{mbean.appCount}"> <f:selectItem itemLabel="1" itemValue="1" /> <f:selectItem itemLabel="2" itemValue="2" /> <f:selectItem itemLabel="3" itemValue="3" /> <f:selectItem itemLabel="4" itemValue="4" /> <f:selectItem itemLabel="5" itemValue="5" /> <p:ajax update="appsContainer" event="change" listener="#{mbean.onChangeNumApps()}" /> </h:selectOneMenu> <p:panel id="appsContainer" > <p:panel header="Application" id="appsPane" value="#{mbean.submittedApps}" var="app" multiple="true"> submittedApps is a List containing the panel form elements. Here is my mbean listener: public void onChangeNumApps() { List<Apps> c = new ArrayList<Apps>(); logger.info("on change event fired"); logger.info("new value is "+mbean.getAppCount()); for (int i=0;i < mbean.getAppCount();i++) { c.add(new App()); } mbean.setSubmittedApps(c); } I am mixing p:ajax with h:selectone because i could not get p:selectone working for some reason - possibly due to a CSS collision with my stylesheet??

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• AutoMapper How To Map Object A To Object B Differently Depending On Context

  - by IanT8

  Calling all AutoMapper gurus! I'd like to be able to map object A to object B differently depending on context at runtime. In particular, I'd like to ignore certain properties in one mapping case, and have all properties mapped in another case. What I'm experiencing is that Mapper.CreateMap can be called successfully in the different mapping cases however, once CreateMap is called, the map for a particular pair of types is set and is not subsequently changed by succeeding CreateMap calls which might describe the mapping differently. I found a blog post which advocates Mapper.Reset() to get round the problem, however, the static nature of the Mapper class means that it is only a matter of time before a collision and crash occur. Is there a way to do this? What I think I need is to call Mapper.CreateMap once per appdomain, and later, be able to call Mapper.Map with hints about which properties should be included / excluded. Right now, I'm thinking about changing the source code by writing a non-static mapping class that holds the mapping config instance based. Poor performance, but thread safe. What are my options. What can be done? Automapper seems so promising.

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• WPF 3D extrude "a bitmap"

  - by Bgnt44

  Hi, I'm looking for a way to simulate a projector in wpf 3D : i've these "in" parameters : beam shape : a black and white bitmap file beam size ( ex : 30 °) beam color beam intensity ( dimmer ) projector position (x,y,z) beam position (pan(x),tilt(y) relative to projector) First i was thinking of using light object but it seem that wpf can't do that So, now i think that i can make for each projector a polygon from my bitmap... First i need to convert the black and white bitmap to vector. Only Simple shape ( bubble, line,dot,cross ...) Is there any WPF way to do that ? Or maybe a external program file (freeware); then i need to build the polygon, with the shape of the converted bitmap , color , size , orientation in parameter. i don't know how can i defined the lenght of the beam , and if it can be infiny ... To show the beam result, i think of making a room ( floor , wall ...) and beam will end to these wall... i don't care of real light render ( dispersion ...) but the scene render has to be real time and at least 15 times / second (with probably from one to 100 projectors at the same time), information about position, angle,shape,color will be sent for each render... Well so, i need sample for that, i guess that all of these things could be useful for other people If you have sample code : Convert Bitmap to vector Extrude vectors from one point with a angle parameter until collision of a wall Set x,y position of the beam depend of the projector position Set Alpha intensity of the beam, color Maybe i'm totally wrong and WPF is not ready for that , so advise me about other way ( xna,d3D ) with sample of course ;-) Thanks you

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• Error when changing default lanuage in asp.net compilation from vb to c#

  - by Herman

  Hi all, We have a updatable web site project that is written in c#, it has the usual web form implementation using master page, skins, user controls,...etc. Up to this point we neglect to change the default compilation language from VB to C#. However, the second we change it, we see the following error. Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at ASP.Default.__DataBinding__control499(Object sender, EventArgs e) at System.Web.UI.Control.OnDataBinding(EventArgs e) at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at System.Web.UI.Control.DataBindChildren() at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at System.Web.UI.Control.DataBindChildren() at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at System.Web.UI.Control.DataBindChildren() at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at System.Web.UI.Control.DataBindChildren() at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at .... Further investigation points out that this error is getting generated from a Theme related assembly (Source : App_Theme_Default.zclakrlo). Any ideas? One of my co-worker suggested that it might be skin file related since we have a theme call "Default" and there is no way to specify a language on a skin file. Therefore, when the asp.net runtime tries to compile it under C#, it will give a name collision? Does this make sense? Any help is appreciated.

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• RESTful API design question - how should one allow users to create new resource instances?

  - by Tamás

  I'm working in a research group where we intend to publish implementations of some of the algorithms we develop on the web via a RESTful API. Most of these algorithms work on small to medium size datasets, and in many cases, a user of our services might want to run multiple queries (with different parameters) on the same dataset, so for me it seems reasonable to allow users to upload their datasets in advance and refer to them in their queries later. In this sense, a dataset could be a resource in my API, and an algorithm could be another. My question is: how should I let the users upload their own datasets? I cannot simply let users upload their data to /dataset/dataset_id as letting the users invent their own dataset_ids might result in ID collision and users overwriting each other's datasets by accident. (I believe one of the most frequently used dataset ID would be test). I think an ideal way would be to have a dedicated URL (like /dataset/upload) where users can POST their datasets and the response would contain a unique ID under which the dataset was stored, but I'm not sure that it does not violate the basic principles of REST. What is the preferred way of dealing with such scenarios?

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• How to route all subdomains to a single host using mDNS?

  - by John Mee

  I have a development webserver hosting as "myhost.local" which is found using Bonjour/mDNS. The server is running avahi-daemon. The webserver also wants to handle any subdomains of itself. Eg "cat.myhost.local" and "dog.myhost.local" and "guppy.myhost.local". Given that myhost.local is on a dynamic ip address from dhcp, is there still a way to route all requests for the subdomains to myhost.local? I'm starting to think it not currently possible... http://marc.info/?l=freedesktop-avahi&m=119561596630960&w=2 You can do this with the /etc/avahi/hosts file. Alternatively you can use avahi-publish-host-name. No, he cannot. Since he wants to define an alias, not a new hostname. I.e. he only wants to register an A RR, no reverse PTR RR. But if you stick something into /etc/avahi/hosts then it registers both, and detects a collision if the PTR RR is non-unique, which would be the case for an alias.

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• web service - client classes

  - by Noona

  The web service that I implemented is up and running, when I try to run the client I get the following error with regard to the classes that were generated using wsimport, Caused by: java.security.PrivilegedActionException: com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 4 counts of IllegalAnnotationExceptions Two classes have the same XML type name "{http://server.agency.hw2/}userJoined". Use @XmlType.name and @XmlType.namespace to assign different names to them. this problem is related to the following location: at hw2.chat.backend.main.generatedfromserver.UserJoined at public javax.xml.bind.JAXBElement hw2.chat.backend.main.generatedfromserver.ObjectFactory.createUserJoined(hw2.chat.backend.main.generatedfromserver.UserJoined) at hw2.chat.backend.main.generatedfromserver.ObjectFactory this problem is related to the following location: at ChatCompany.BackendChatServer.hw2.chat.backend.main.generatedfromserver.UserJoined Two classes have the same XML type name "{http://server.agency.hw2/}userJoinedResponse". Use @XmlType.name and @XmlType.namespace to assign different names to them. this problem is related to the following location: at hw2.chat.backend.main.generatedfromserver.UserJoinedResponse at public javax.xml.bind.JAXBElement hw2.chat.backend.main.generatedfromserver.ObjectFactory.createUserJoinedResponse(hw2.chat.backend.main.generatedfromserver.UserJoinedResponse) But I can't figure out what exactly is meant by the error. I am assuming I need to change something in annotations in this class as pointed out by the compiler: @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "userJoinedResponse") public class UserJoinedResponse { } could someone please point out why there's a name collision and what annotations I need to change? thanks

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• Official names for pointer operators

  - by FredOverflow

  What are the official names for the operators * and & in the context of pointers? They seem to be frequently called dereference operator and address-of operator respectively, but unfortunately, the section on unary operators in the standard does not name them. I really don't want to name & address-of anymore, because & returns a pointer, not an address. (A pointer is a language mechanism, while an address is an implementation detail. Addresses are untyped, while pointers aren't, except for void*.) The standard is very clear about this: The result of the unary & operator is a pointer to its operand. Symmetry suggests to name & reference operator which is a little unfortunate because of the collision with references in C++. The fact that & returns a pointer suggests pointer operator. Are there any official sources that would confirm these (or other) namings?

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• Can't create an OgreBullet Trimesh

  - by Nathan Baggs

  I'm using Ogre and Bullet for a project and I currently have a first person camera set up with a Capsule Collision Shape. I've created a model of a cave (which will serve as the main part of the level) and imported it into my game. I'm now trying to create an OgreBulletCollisions::TriangleMeshCollisionShape of the cave. The code I've got so far is this but it isn't working. It compiles but the Capsule shape passes straight through the cave shape. Also I have debug outlines on and there are none being drawn around the cave mesh. Entity *cave = mSceneMgr->createEntity("Cave", "pCube1.mesh"); SceneNode *caveNode = mSceneMgr->getRootSceneNode()->createChildSceneNode(); caveNode->setPosition(0, 10, 250); caveNode->setScale(10, 10, 10); caveNode->rotate(Quaternion(0.5, 0.5, -0.5, 0.5)); caveNode->attachObject(cave); OgreBulletCollisions::StaticMeshToShapeConverter *smtsc = new OgreBulletCollisions::StaticMeshToShapeConverter(); smtsc->addEntity(cave); OgreBulletCollisions::TriangleMeshCollisionShape *tri = smtsc->createTrimesh(); OgreBulletDynamics::RigidBody *caveBody = new OgreBulletDynamics::RigidBody("cave", mWorld); caveBody->setStaticShape(tri, 0.1, 0.8); mShapes.push_back(tri); mBodies.push_back(caveBody); Any suggestions are welcome. To clarify. It compiles but the Capsule shape passes straight through the cave shape. Also I have debug outlines on and there are none being drawn around the cave mesh

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• Using MD5 to generate an encryption key from password?

  - by Charles

  I'm writing a simple program for file encryption. Mostly as an academic exercise but possibly for future serious use. All of the heavy lifting is done with third-party libraries, but putting the pieces together in a secure manner is still quite a challenge for the non-cryptographer. Basically, I've got just about everything working the way I think it should. I'm using 128-bit AES for the encryption with a 128-bit key length. I want users to be able to enter in variable-length passwords, so I decided to hash the password with MD5 and then use the hash as the key. I figured this was acceptable--the key is always supposed to be a secret, so there's no reason to worry about collision attacks. Now that I've implemented this, I ran across a couple articles indicating that this is a bad idea. My question is: why? If a good password is chosen, the cipher is supposed to be strong enough on its own to never reveal the key except via an extraordinary (read: currently infeasible) brute-force effort, right? Should I be using something like PBKDF2 to generate the key or is that just overkill for all but the most extreme cryptographic applications?

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• Make winform run away from the mouse.

  - by JACK IN THE CRACK

  Okay so I'm trying to make a little gag program that will "run away" from the mouse. So, to get the mouse coordinates for the whole screen and not just the form control I had to create a little helper: static class MouseHelper { [DllImport("user32.dll")] [return: MarshalAs(UnmanagedType.Bool)] internal static extern bool GetCursorPos(ref Point pt); public static Point GetPosition() { Point w32Mouse = new Point(); GetCursorPos(ref w32Mouse); return w32Mouse; } } Now I thought I was going to use the MouseMove event... but that doesn't work for outside the form control either so I have an auto-enabled timer on a 10ms loop called timerMouseMove. public partial class Form1 : Form { public Form1() { InitializeComponent(); } private bool CollisionCheck() { Point win32Mouse = MouseHelper.GetPosition(); if (win32Mouse.X <= Location.X || win32Mouse.X >= (Location.X + Width)) return false; if (win32Mouse.Y <= Location.Y || win32Mouse.Y >= (Location.Y + Height)) return false; return true; } private void timerMouseMove_Tick(object sender, EventArgs e) { if (CollisionCheck()) Location = new Point(Location.X + 1, Location.Y + 1); } } So this works out nicely, at least I have the collision checking working and whatnot. But now, how should I go about figuring which side of the form the mouse has collided with, so that I can update its location to move in the opposite direction the mouse collides with it? And such halp

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• Implementing Model-level caching

  - by Byron

  I was posting some comments in a related question about MVC caching and some questions about actual implementation came up. How does one implement a Model-level cache that works transparently without the developer needing to manually cache, yet still remains efficient? I would keep my caching responsibilities firmly within the model. It is none of the controller's or view's business where the model is getting data. All they care about is that when data is requested, data is provided - this is how the MVC paradigm is supposed to work. (Source: Post by Jarrod) The reason I am skeptical is because caching should usually not be done unless there is a real need, and shouldn't be done for things like search results. So somehow the Model itself has to know whether or not the SELECT statement being issued to it worthy of being cached. Wouldn't the Model have to be astronomically smart, and/or store statistics of what is being most often queried over a long period of time in order to accurately make a decision? And wouldn't the overhead of all this make the caching useless anyway? Also, how would you uniquely identify a query from another query (or more accurately, a resultset from another resultset)? What about if you're using prepared statements, with only the parameters changing according to user input? Another poster said this: I would suggest using the md5 hash of your query combined with a serialized version of your input arguments. This would require twice the number of serialization options. I was under the impression that serialization was quite expensive, and for large inputs this might be even worse than just re-querying. And is the minuscule chance of collision worth worrying about? Conceptually, caching in the Model seems like a good idea to me, but it seems in practicality the developer should have direct control over caching and write it into the controller. Thoughts/ideas? Edit: I'm using PHP and MySQL if that helps to narrow your focus.

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• How to do cleanup reliably in python?

  - by Cheery

  I have some ctypes bindings, and for each body.New I should call body.Free. The library I'm binding doesn't have allocation routines insulated out from the rest of the code (they can be called about anywhere there), and to use couple of useful features I need to make cyclic references. I think It'd solve if I'd find a reliable way to hook destructor to an object. (weakrefs would help if they'd give me the callback just before the data is dropped. So obviously this code megafails when I put in velocity_func: class Body(object): def __init__(self, mass, inertia): self._body = body.New(mass, inertia) def __del__(self): print '__del__ %r' % self if body: body.Free(self._body) ... def set_velocity_func(self, func): self._body.contents.velocity_func = ctypes_wrapping(func) I also tried to solve it through weakrefs, with those the things seem getting just worse, just only largely more unpredictable. Even if I don't put in the velocity_func, there will appear cycles at least then when I do this: class Toy(object): def __init__(self, body): self.body.owner = self ... def collision(a, b, contacts): whatever(a.body.owner) So how to make sure Structures will get garbage collected, even if they are allocated/freed by the shared library? There's repository if you are interested about more details: http://bitbucket.org/cheery/ctypes-chipmunk/

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• Password hashing, salt and storage of hashed values

  - by Jonathan Leffler

  Suppose you were at liberty to decide how hashed passwords were to be stored in a DBMS. Are there obvious weaknesses in a scheme like this one? To create the hash value stored in the DBMS, take: A value that is unique to the DBMS server instance as part of the salt, And the username as a second part of the salt, And create the concatenation of the salt with the actual password, And hash the whole string using the SHA-256 algorithm, And store the result in the DBMS. This would mean that anyone wanting to come up with a collision should have to do the work separately for each user name and each DBMS server instance separately. I'd plan to keep the actual hash mechanism somewhat flexible to allow for the use of the new NIST standard hash algorithm (SHA-3) that is still being worked on. The 'value that is unique to the DBMS server instance' need not be secret - though it wouldn't be divulged casually. The intention is to ensure that if someone uses the same password in different DBMS server instances, the recorded hashes would be different. Likewise, the user name would not be secret - just the password proper. Would there be any advantage to having the password first and the user name and 'unique value' second, or any other permutation of the three sources of data? Or what about interleaving the strings? Do I need to add (and record) a random salt value (per password) as well as the information above? (Advantage: the user can re-use a password and still, probably, get a different hash recorded in the database. Disadvantage: the salt has to be recorded. I suspect the advantage considerably outweighs the disadvantage.) There are quite a lot of related SO questions - this list is unlikely to be comprehensive: Encrypting/Hashing plain text passwords in database Secure hash and salt for PHP passwords The necessity of hiding the salt for a hash Clients-side MD5 hash with time salt Simple password encryption Salt generation and Open Source software I think that the answers to these questions support my algorithm (though if you simply use a random salt, then the 'unique value per server' and username components are less important).

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• Qt MOC Filename Collisions using multiple .pri files

  - by Skinniest Man

  In order to keep my Qt project somewhat organized (using Qt Creator), I've got one .pro file and multiple .pri files. Just recently I added a class to one of my .pri files that has the same filename as a class that already existed in a separate .pri file. The file structure and makefiles generated by qmake appear to be oblivious to the filename collision that ensues. The generated moc_* files all get thrown into the same subdirectory (either release or debug, depending) and one ends up overwriting the other. When I try to make the project, I get several warnings that look like this: Makefile.Release:318: warning: overriding commands for target `release/moc_file.cpp` And the project fails to link. Here is a simple example of what I'm talking about. Directory structure: + project_dir | + subdir1 | | - file.h | | - file.cpp | + subdir2 | | - file.h | | - file.cpp | - main.cpp | - project.pro | - subdir1.pri | - subdir2.pri Contents of project.pro: TARGET = project TEMPLATE = app include(subdir1.pri) include(subdir2.pri) SOURCES += main.cpp Contents of subdir1.pri: HEADERS += subdir1/file.h SOURCES += subdir1/file.cpp Contents of subdir2.pri: HEADERS += subdir2/file.h SOURCES += subdir2/file.cpp Is there a way to tell qmake to generate a system that puts the moc_* files from separate .pri files into separate subdirectories?

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• no more hitcollision at 1 life

  - by user1449547

  So I finally got my implementation of lives fixed, and it works. Now however when I collide with a ghost when I am at 1 life, nothing happens. I can fall to my death enough times for a game over. from what i can tell the problem is that hit collision is not longer working, because it does not detect a hit, I do not fall. the question is why? update if i kill myself fast enough it works, but if i play for like 30 seconds, it stops the hit collision detection on my ghosts. platforms and springs still work. public class World { public interface WorldListener { public void jump(); public void highJump(); public void hit(); public void coin(); public void dying(); } public static final float WORLD_WIDTH = 10; public static final float WORLD_HEIGHT = 15 * 20; public static final int WORLD_STATE_RUNNING = 0; public static final int WORLD_STATE_NEXT_LEVEL = 1; public static final int WORLD_STATE_GAME_OVER = 2; public static final Vector2 gravity = new Vector2(0, -12); public Hero hero; public final List<Platform> platforms; public final List<Spring> springs; public final List<Ghost> ghosts; public final List<Coin> coins; public Castle castle; public final WorldListener listener; public final Random rand; public float heightSoFar; public int score; public int state; public int lives=3; public World(WorldListener listener) { this.hero = new Hero(5, 1); this.platforms = new ArrayList<Platform>(); this.springs = new ArrayList<Spring>(); this.ghosts = new ArrayList<Ghost>(); this.coins = new ArrayList<Coin>(); this.listener = listener; rand = new Random(); generateLevel(); this.heightSoFar = 0; this.score = 0; this.state = WORLD_STATE_RUNNING; } private void generateLevel() { float y = Platform.PLATFORM_HEIGHT / 2; float maxJumpHeight = Hero.hero_JUMP_VELOCITY * Hero.hero_JUMP_VELOCITY / (2 * -gravity.y); while (y < WORLD_HEIGHT - WORLD_WIDTH / 2) { int type = rand.nextFloat() > 0.8f ? Platform.PLATFORM_TYPE_MOVING : Platform.PLATFORM_TYPE_STATIC; float x = rand.nextFloat() * (WORLD_WIDTH - Platform.PLATFORM_WIDTH) + Platform.PLATFORM_WIDTH / 2; Platform platform = new Platform(type, x, y); platforms.add(platform); if (rand.nextFloat() > 0.9f && type != Platform.PLATFORM_TYPE_MOVING) { Spring spring = new Spring(platform.position.x, platform.position.y + Platform.PLATFORM_HEIGHT / 2 + Spring.SPRING_HEIGHT / 2); springs.add(spring); } if (rand.nextFloat() > 0.7f) { Ghost ghost = new Ghost(platform.position.x + rand.nextFloat(), platform.position.y + Ghost.GHOST_HEIGHT + rand.nextFloat() * 3); ghosts.add(ghost); } if (rand.nextFloat() > 0.6f) { Coin coin = new Coin(platform.position.x + rand.nextFloat(), platform.position.y + Coin.COIN_HEIGHT + rand.nextFloat() * 3); coins.add(coin); } y += (maxJumpHeight - 0.5f); y -= rand.nextFloat() * (maxJumpHeight / 3); } castle = new Castle(WORLD_WIDTH / 2, y); } public void update(float deltaTime, float accelX) { updatehero(deltaTime, accelX); updatePlatforms(deltaTime); updateGhosts(deltaTime); updateCoins(deltaTime); if (hero.state != Hero.hero_STATE_HIT) checkCollisions(); checkGameOver(); checkFall(); } private void updatehero(float deltaTime, float accelX) { if (hero.state != Hero.hero_STATE_HIT && hero.position.y <= 0.5f) hero.hitPlatform(); if (hero.state != Hero.hero_STATE_HIT) hero.velocity.x = -accelX / 10 * Hero.hero_MOVE_VELOCITY; hero.update(deltaTime); heightSoFar = Math.max(hero.position.y, heightSoFar); } private void updatePlatforms(float deltaTime) { int len = platforms.size(); for (int i = 0; i < len; i++) { Platform platform = platforms.get(i); platform.update(deltaTime); if (platform.state == Platform.PLATFORM_STATE_PULVERIZING && platform.stateTime > Platform.PLATFORM_PULVERIZE_TIME) { platforms.remove(platform); len = platforms.size(); } } } private void updateGhosts(float deltaTime) { int len = ghosts.size(); for (int i = 0; i < len; i++) { Ghost ghost = ghosts.get(i); ghost.update(deltaTime); if (ghost.state == Ghost.GHOST_STATE_DYING && ghost.stateTime > Ghost.GHOST_DYING_TIME) { ghosts.remove(ghost); len = ghosts.size(); } } } private void updateCoins(float deltaTime) { int len = coins.size(); for (int i = 0; i < len; i++) { Coin coin = coins.get(i); coin.update(deltaTime); } } private void checkCollisions() { checkPlatformCollisions(); checkGhostCollisions(); checkItemCollisions(); checkCastleCollisions(); } private void checkPlatformCollisions() { if (hero.velocity.y > 0) return; int len = platforms.size(); for (int i = 0; i < len; i++) { Platform platform = platforms.get(i); if (hero.position.y > platform.position.y) { if (OverlapTester .overlapRectangles(hero.bounds, platform.bounds)) { hero.hitPlatform(); listener.jump(); if (rand.nextFloat() > 0.5f) { platform.pulverize(); } break; } } } } private void checkGhostCollisions() { int len = ghosts.size(); for (int i = 0; i < len; i++) { Ghost ghost = ghosts.get(i); if (hero.position.y < ghost.position.y) { if (OverlapTester.overlapRectangles(ghost.bounds, hero.bounds)){ hero.hitGhost(); listener.hit(); } break; } else { if(hero.position.y > ghost.position.y) { if (OverlapTester.overlapRectangles(hero.bounds, ghost.bounds)){ hero.hitGhostJump(); listener.jump(); ghost.dying(); score += Ghost.GHOST_SCORE; } break; } } } } private void checkItemCollisions() { int len = coins.size(); for (int i = 0; i < len; i++) { Coin coin = coins.get(i); if (OverlapTester.overlapRectangles(hero.bounds, coin.bounds)) { coins.remove(coin); len = coins.size(); listener.coin(); score += Coin.COIN_SCORE; } } if (hero.velocity.y > 0) return; len = springs.size(); for (int i = 0; i < len; i++) { Spring spring = springs.get(i); if (hero.position.y > spring.position.y) { if (OverlapTester.overlapRectangles(hero.bounds, spring.bounds)) { hero.hitSpring(); listener.highJump(); } } } } private void checkCastleCollisions() { if (OverlapTester.overlapRectangles(castle.bounds, hero.bounds)) { state = WORLD_STATE_NEXT_LEVEL; } } private void checkFall() { if (heightSoFar - 7.5f > hero.position.y) { --lives; hero.hitSpring(); listener.highJump(); } } private void checkGameOver() { if (lives<=0) { state = WORLD_STATE_GAME_OVER; } } }

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• Effective communication in a component-based system

  - by Tesserex

  Yes, this is another question about my game engine, which is coming along very nicely, with much thanks to you guys. So, if you watched the video (or didn't), the objects in the game are composed of various components for things like position, sprites, movement, collision, sounds, health, etc. I have several message types defined for "tell" type communication between entities and components, but this only goes so far. There are plenty of times when I just need to ask for something, for example an entity's position. There are dozens of lines in my code that look like this: SomeComponent comp = (SomeComponent)entity.GetComponent(typeof(SomeComponent)); if (comp != null) comp.GetSomething(); I know this is very ugly, and I know that casting smells of improper OO design. But as complex as things are, there doesn't seem to be a better way. I could of course "hard-code" my component types and just have SomeComponent comp = entity.GetSomeComponent(); but that seems like a cop-out, and a bad one. I literally JUST REALIZED, while writing this, after having my code this way for months with no solution, that a generic will help me. SomeComponent comp = entity.GetComponent<SomeComponent>(); Amazing how that works. Anyway, this is still only a semantic improvement. My questions remain. Is this actually that bad? What's a better alternative?

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• How to handle ids and polymorphic associations in views if compound keys are not supported?

  - by duncan

  I have a Movie plan table: movie_plans (id, description) Each plan has items, which describe a sequence of movies and the duration in minutes: movie_plan_items (id, movie_plan_id, movie_id, start_minutes, end_minutes) A specific instance of that plan happens in: movie_schedules (id, movie_plan_id, start_at) However the schedule items can be calculated from the movie_plan_items and the schedule start time by adding the minutes create view movie_schedule_items as select CONCAT(p.id, '-', s.id) as id, s.id as movie_schedule_id, p.id as movie_plan_item_id, p.movie_id, p.movie_plan_id, (s.start_at + INTERVAL p.start_minutes MINUTE) as start_at, (s.start_at + INTERVAL p.end_minutes MINUTE) as end_at from movie_plan_items p, movie_schedules s where s.movie_plan_id=p.movie_plan_id; I have a model over this view (readonly), it works ok, except that the id is right now a string. I now want to add a polymorphic property (like comments) to various of the previous tables. Therefore for movie_schedule_items I need a unique and persistent numeric id. I have the following dilemma: I could avoid the id and have movie_schedule_items just use the movie_plan_id and movie_schedule_id as a compound key, as it should. But Rails sucks in this regard. I could create an id using String#hash or a md5, thus making it slower or collision prone (and IIRC String#hash is no longer persistent across processes in Ruby 1.9) Any ideas on how to handle this situation?

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