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• Bluetooth to arduino

  - by user1833709

  My current project includes an Arduino Uno attached via USB to a laptop. The laptop is there is receive messages via bluetooth (I realize I could connect a bluetooth modem directly to the arduino but this project has to come in under budget). What I'd ideally like to do is write a program that continually checks whether the laptop has been paired to a bluetooth transmitter (my phone) and sends this to the arduino. Do you think should write a program that checks the bluetooth state and writes a 0 or 1 to a text document, and then use something like Gobetwino to read from the text document? I could probably figure out how to continually read from the file, but I don't know enough about bluetooth to know how to check whether it's paired or not, computer-side. Something that writes directly to the arduino instead of a text document would be my preference, but I don't know where to start. I'm using an Android phone and Windows 7. If you need more info about the setup, just ask. Does anyone have any experience with this?

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• J-Monkey subclass

  - by user2971104

  I'm new in java and J-monkey and I'm trying to make a java game so for the Menu I have made a enum so I can Switch between any of my State but I want to keep the main file shorter so it can be easily to read so I'm making subclass the problem is that when run the game it give me an error that say "Uncaught exception thrown in Thread[LWJGL Renderer Thread,5,main] NullPointerException" I think this problem has to be something whit the pipeline Here is the code of my main file: package mygame; import com.jme3.app.SimpleApplication; import com.jme3.font.BitmapText; import com.jme3.material.Material; import com.jme3.math.ColorRGBA; import com.jme3.math.Vector3f; import com.jme3.renderer.RenderManager; import com.jme3.scene.Spatial; import com.jme3.scene.Geometry; import com.jme3.input.*; import com.jme3.input.controls.*; public class Main extends SimpleApplication { //GameStates enum GameState{Logo, Menu, Playing, Option}; GameState gameState = GameState.Logo; //Class Variables Logo logo; public Main() { logo = new Logo(); } public static void main(String[] args) { Main app = new Main(); app.start(); } public static void logo(String[] args) { Logo app = new Logo(); app.start(); } @Override public void simpleInitApp() { //Load flyCam.setMoveSpeed(20); if(gameState == GameState.Logo){ logo.simpleInitApp(); } } @Override public void simpleUpdate(float tpf) { } @Override public void simpleRender(RenderManager rm) { //TODO: add render code //Load if(gameState == GameState.Logo) { } } } And here is my Logo subclass: package mygame; import com.jme3.app.SimpleApplication; import com.jme3.renderer.RenderManager; import com.jme3.scene.Spatial; public class Logo extends SimpleApplication { @Override public void simpleInitApp() { Spatial Logo_Model = assetManager.loadModel("Models/Teapot/Logo.obj"); rootNode.attachChild(Logo_Model); } public void simpleRender(RenderManager rm) { //Load } }

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• Partial slideDown with jQuery

  - by Jon

  I have some buttons that have drawer menus and what I'd like to do is add a state so that when the user hovers over the button, the drawer bumps out slightly (maybe with a little wiggle/rubber-banding) so that they know that there's a drawer with more information. I have the sliding working and a hover function set up, but I don't know how to implement a partial slideDown. Any ideas? FIDDLE. Code: <div class="clause"> <div class="icon"><img src="http://i.imgur.com/rTu40.png"/></div> <div class="label">Location</div> <div class="info">Midwest > Indiana, Kentucky; Southwest > Texas, Nevada, Utah; Pacific > California, Hawaii</div> </div> <div class="drawer">Info 1<br/><br/></div> <div class="drawerBottom"></div> $(".clause").click(function() { var tmp = $(this).next("div.drawer"); if(tmp.is(":hidden")) tmp.slideDown('3s'); else tmp.slideUp('3s'); }); $(".clause").hover(function() { });

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• Implementing a bitfield using java enums

  - by soappatrol

  Hello, I maintain a large document archive and I often use bit fields to record the status of my documents during processing or when validating them. My legacy code simply uses static int constants such as: static int DOCUMENT_STATUS_NO_STATE = 0 static int DOCUMENT_STATUS_OK = 1 static int DOCUMENT_STATUS_NO_TIF_FILE = 2 static int DOCUMENT_STATUS_NO_PDF_FILE = 4 This makes it pretty easy to indicate the state a document is in, by setting the appropriate flags. For example: status = DOCUMENT_STATUS_NO_TIF_FILE | DOCUMENT_STATUS_NO_PDF_FILE; Since the approach of using static constants is bad practice and because I would like to improve the code, I was looking to use Enums to achieve the same. There are a few requirements, one of them being the need to save the status into a database as a numeric type. So there is a need to transform the enumeration constants to a numeric value. Below is my first approach and I wonder if this is the correct way to go about this? class DocumentStatus{ public enum StatusFlag { DOCUMENT_STATUS_NOT_DEFINED(1<<0), DOCUMENT_STATUS_OK(1<<1), DOCUMENT_STATUS_MISSING_TID_DIR(1<<2), DOCUMENT_STATUS_MISSING_TIF_FILE(1<<3), DOCUMENT_STATUS_MISSING_PDF_FILE(1<<4), DOCUMENT_STATUS_MISSING_OCR_FILE(1<<5), DOCUMENT_STATUS_PAGE_COUNT_TIF(1<<6), DOCUMENT_STATUS_PAGE_COUNT_PDF(1<<7), DOCUMENT_STATUS_UNAVAILABLE(1<<8), private final long statusFlagValue; StatusFlag(long statusFlagValue) { this.statusFlagValue = statusFlagValue } public long getStatusFlagValue(){ return statusFlagValue } } /** * Translates a numeric status code into a Set of StatusFlag enums * @param numeric statusValue * @return EnumSet representing a documents status */ public EnumSet<StatusFlag> getStatusFlags(long statusValue) { EnumSet statusFlags = EnumSet.noneOf(StatusFlag.class) StatusFlag.each { statusFlag -> long flagValue = statusFlag.statusFlagValue if ( (flagValue&statusValue ) == flagValue ) { statusFlags.add(statusFlag) } } return statusFlags } /** * Translates a set of StatusFlag enums into a numeric status code * @param Set if statusFlags * @return numeric representation of the document status */ public long getStatusValue(Set<StatusFlag> flags) { long value=0 flags.each { statusFlag -> value|=statusFlag.getStatusFlagValue() } return value } public static void main(String[] args) { DocumentStatus ds = new DocumentStatus(); Set statusFlags = EnumSet.of( StatusFlag.DOCUMENT_STATUS_OK, StatusFlag.DOCUMENT_STATUS_UNAVAILABLE) assert ds.getStatusValue( statusFlags )==258 // 0000.0001|0000.0010 long numericStatusCode = 56 statusFlags = ds.getStatusFlags(numericStatusCode) assert !statusFlags.contains(StatusFlag.DOCUMENT_STATUS_OK) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_TIF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_PDF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_OCR_FILE) } }

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• Load In and Animate content

  - by crozer

  Hello, I have a little issue concerning an animation-effect which loads a certain div into the body of the site. Let me be more precise: I have a div with the id 'contact': <div id="contact">content</div> The jquery code loads the contents within that div, when I press the link with the id 'ajax_contact': <a href="#" id="ajax_contact">link</a>. The code is working perfectly. However, I want #contact to be HIDDEN when the site loads, i.e. the default state must be non-visible. Only when the user clicks the link #ajax_contact, the div must appear. Please have a look at the jquery code: $(document).ready(function() { var hash = window.location.hash.substr(1); var href = $('#ajax_contact').each(function(){ var href = $(this).attr('href'); if(hash==href.substr(0,href.length-5)){ var toLoad = hash+'.html #contact'; $('#contact').load(toLoad) } }); $('#ajax_contact').click(function(){ var toLoad = $(this).attr('href')+' #contact'; $('#contact').hide('fast',loadContent); $('#load').remove(); $('body').append('<span id="load">LOADING...</span>'); $('#load').fadeIn('normal'); window.location.hash = $(this).attr('href').substr(0,$(this).attr('href').length-5); function loadContent() { $('#contact').load(toLoad,'',showNewContent()) } function showNewContent() { $('#contact').show('normal',hideLoader()); } function hideLoader() { $('#load').fadeOut('normal'); } return false; }); }); I am not sure whether I must change something inside the HTML, but I believe the key is inside the jquery-code. I also tried giving the #contact a CSS style of visible:none, yet this loops and makes the jquery impossible to load the #contact in. I hope I've explained myself well; thank you very much in advance. Chris

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• force refresh of part of page in browser

  - by Jeremy

  I have the following html: <ul class="scr"> <li class="scr"> <input type="checkbox" class="chkscr"/> <h3>Item Name</h3> <div class="scr">Contents</div> </li> .... </ul> And the following jQuery: //Set initial state of each scr section $('.chkscr input, input.chkscr').each(function() { chkSCR_Click($(this)); }); //Setup click event $('.chkscr input, input.chkscr').click(function() { chkSCR_Click($(this)); }); //Toggle corresponding scr section for the checkbox function chkSCR_Click(ctl) { if (ctl.attr('checked')) { ctl.parents('li.scr').find('div.scr').stop().show(); } else { ctl.parents('li.scr').find('div.scr').stop().hide(); } } My issue is that when I toggle the last li element to display, the h3 element contents disapear, until I click somewhere else on the page, or scroll the page up and down to cause the browse to repaint that portion of the window. I don't get this behavior in Opera for example, and even in IE the behavior only happens on the last li element, so I'm pretty sure it's an IE quirk and not my code. Is there any workaround I can do through jquery/javascript to force it to repaint the h3 element?

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• XNA: What can cause SpriteBatch.End() to throw a NRE?

  - by Rosarch

  I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm.... UPDATE 2: This does cause an NRE: protected override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.End(); // boned here //screenManager.Draw(gameTime); base.Draw(gameTime); }

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• IE7/IE8 javascript drop down menu used to redirect not working

  - by Robbiegod

  The error I see from IE7/IE8 in Jquery v1.7.2 and v.1.7.1 - i tried both: SCRIPT438: Object doesn't support property or method 'apply' My Code: <form> <select id="stateD" OnChange="showState()"> <option value="none" selected="selected">==========</option> <option value="http://www.google.com">google</option> <option value="http://www.yahoo.com">Yahoo</option> </select> </form> My Javascript - I have this pasted just below the webform: <script type="text/javascript"> function showState(){ oStates = document.getElementById("stateD"); var jLink = $("#stateD :selected").val(); if (jLink == undefined || jLink == "none" ){ alert("Please Select a State"); } else{ document.location.href=jLink}; } </script> I'm not using 2 libraries so i don't get why its having a problem. All that is supposed to happen is you select a url from the drop down menu and it auto sends you to that url that is in the value of the option tag. Works everywhere else, not sure why IE has to be such a jerk today. I'd post a url but i can't at the moment. its private. has anyone encountered this issue before?

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• Reserve space for initially hidden widget in QVBoxLayout

  - by Skinniest Man

  I am using a QVBoxLayout to arrange a vertical stack of widgets. I want some of them to be initially hidden and only show up when a check box is checked. Here is an example of the code I'm using. MyWidget::MyWidget(QWidget *parent) : QWidget(parent) { QVBoxLayout *layout = new QVBoxLayout(this); QLabel *labelLogTypes = new QLabel(tr("Log Types")); m_checkBoxCsv = new QCheckBox(tr("&Delimited File (CSV)")); m_labelDelimiter = new QLabel(tr("Delimiter:")); m_lineEditDelimiter = new QLineEdit(","); checkBoxCsv_Toggled(m_checkBoxCsv-isChecked()); connect(m_checkBoxCsv, SIGNAL(toggled(bool)), SLOT(checkBoxCsv_Toggled(bool))); QHBoxLayout *layoutDelimitedChar = new QHBoxLayout(); layoutDelimitedChar-addWidget(m_labelDelimiter); layoutDelimitedChar-addWidget(m_lineEditDelimiter); m_checkBoxXml = new QCheckBox(tr("&XML File")); m_checkBoxText = new QCheckBox(tr("Plain &Text File")); // Now that everything is constructed, put it all together // in the main layout. layout-addWidget(labelLogTypes); layout-addWidget(m_checkBoxCsv); layout-addLayout(layoutDelimitedChar); layout-addWidget(m_checkBoxXml); layout-addWidget(m_checkBoxText); layout-addStretch(); } MyWidget::checkBoxCsv_Toggled(bool checked) { m_labelDelimiter-setVisible(checked); m_lineEditDelimiter-setVisible(checked); } I want m_labelDelimiter and m_lineEditDelimiter both to be initially invisible and I want their visibility to toggle with the state of m_checkBoxCsv. This code acheives the functionality I desire, but it doesn't seem to reserve space for the two initially hidden widgets. When I check the checkbox, they become visible, but everything is kind of scrunched to accomodate them. If I leave them initially visible, everything is laid out just the way I would like it. Is there any way to make the QVBoxLayout reserve space for these widgets even if they're initially invisible?

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• Does anyone still believe in the Capability Maturity Model for Software?

  - by Ed Guiness

  Ten years ago when I first encountered the CMM for software I was, I suppose like many, struck by how accurately it seemed to describe the chaotic "level one" state of software development in many businesses, particularly with its reference to reliance on heroes. It also seemed to provide realistic guidance for an organisation to progress up the levels improving their processes. But while it seemed to provide a good model and realistic guidance for improvement, I never really witnessed an adherence to CMM having a significant positive impact on any organisation I have worked for, or with. I know of one large software consultancy that claims CMM level 5 - the highest level - when I can see first hand that their processes are as chaotic, and the quality of their software products as varied, as other, non-CMM businesses. So I'm wondering, has anyone seen a real, tangible benefit from adherence to process improvement according to CMM? And if you have seen improvement, do you think that the improvement was specifically attributable to CMM, or would an alternative approach (such as six-sigma) have been equally or more beneficial? Does anyone still believe? As an aside, for those who haven't yet seen it, check out this funny-because-its-true parody

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• Git: HEAD has disappeared, want to merge it into master.

  - by samgoody

  The top image is the output of: git reflog. The bottom is what GITK in GIT GUI (msysgit) shows me when I look at all branch history. The last few commits do not show on GIT GUI. Why do they not show on GITK (at least as a branch or something)? How do I merge them into master? I gather this happened when I checked out tag 0.42. Why is that not the same as master? (I had tagged the master in its latest state) When I click push, why does the remote repo claim to be up to date.. shouldn't it try to update these commits into whatever branch they are in? The first of the questions is important - I would like to begin to understand what GIT is thinking. It's more oracle than logic at this point. If it makes a difference to see the earlier history, the project is a [pretty powerful] JS color picker that can be viewed here in its entirety.

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• What to call factory-like (java) methods used with immutable objects

  - by StaxMan

  When creating classes for "immutable objects" immutable meaning that state of instances can not be changed; all fields assigned in constructor) in Java (and similar languages), it is sometimes useful to still allow creation of modified instances. That is, using an instance as base, and creating a new instance that differs by just one property value; other values coming from the base instance. To give a simple example, one could have class like: public class Circle { final double x, y; // location final double radius; public Circle(double x, double y, double r) { this.x = x; this.y = y; this.r = r; } // method for creating a new instance, moved in x-axis by specified amount public Circle withOffset(double deltaX) { return new Circle(x+deltaX, y, radius); } } So: what should method "withOffset" be called? (note: NOT what its name ought to be -- but what is this class of methods called). Technically it is kind of a factory method, but somehow that does not seem quite right to me, since often factories are just given basic properties (and are either static methods, or are not members of the result type but factory type). So I am guessing there should be a better term for such methods. Since these methods can be used to implement "fluent interface", maybe they could be "fluent factory methods"? Better suggestions? EDIT: as suggested by one of answers, java.math.BigDecimal is a good example with its 'add', 'subtract' (etc) methods. Also: I noticed that there's this question (by Jon Skeet no less) that is sort of related (although it asks about specific name for method)

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• how to update a table in c# using oledb parameters?

  - by sameer

  I am having a table which has three fields, namely LM_code,M_Name,Desc. LC_code is a autogenerated string Id, keeping this i am updating M_Name and Desc. I used normal update command, the value is passing in runtime but the fields are not getting updated. I hope using oledb parameters the fileds can be updated. Any help will be appreciated... Here is my code. public void Modify() { String query = "Update Master_Accounts set (M_Name='" + M_Name + "',Desc='" + Desc + "') where LM_code='" + LM_code + "'"; DataManager.RunExecuteNonQuery(ConnectionString.Constr, query); } In DataManager Class i am executing the query string. public static void RunExecuteNonQuery(string Constr, string query) { OleDbConnection myConnection = new OleDbConnection(Constr); try { myConnection.Open(); OleDbCommand myCommand = new OleDbCommand(query, myConnection); myCommand.ExecuteNonQuery(); } catch (Exception ex) { string Message = ex.Message; throw ex; } finally { if (myConnection.State == ConnectionState.Open) myConnection.Close(); } } private void toolstModify_Click_1(object sender, EventArgs e) { txtamcode.Enabled = true; jewellery.LM_code = txtamcode.Text; jewellery.M_Name = txtaccname.Text; jewellery.Desc = txtdesc.Text; jewellery.Modify(); MessageBox.Show("Data Updated Succesfully"); }

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• Retrieving license type (linux/windows/windows+sqlserver) for an Amazon EC2 instance via the API?

  - by Geir

  I need to calculate the hourly running costs for my Amazon EC2 instances. This varies even between instances with same hardware configs (instance types) because I use different amazon images (AMIs): some plain windows server and some windows server with sql server (both of them have additional costs compared with plain linux instances) The EC2 Java API has a describeInstances() method which returns Instance objects with metadata such as instance id, instance type (m1.small/large...), state (running,stopped..) public ip, etc. This Instance object also has a .getLicense().getPool() which according to the Java API should return "The license pool from which this license was used (ex: 'windows')." I thought this is were it may also give 'windows+sqlserver' or something to that effect. The getLicense() method does however return null.. I've navigated around the EC2 web console, not being able to find this information, but I'm hoping that it is possible - otherwise it would mean that you cannot identify the true hourly cost of an particular instance unless you know which AMI was used to create it in the first place (plain windows server or windows server with sql server). Anyone? Thanks :) /Geir

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• Is encrypting session id (or other authenticate value) in cookie useful at all?

  - by Ji

  In web development, when session state is enabled, a session id is stored in cookie(in cookieless mode, query string will be used instead). In asp.net, the session id is encrypted automatically. There are plenty of topics on the internet regarding how you should encrypt your cookie, including session id. I can understand why you want to encrypt private info such as DOB, but any private info should not be stored in cookie at first place. So for other cookie values such as session id, what is the purpose encryption? Does it add security at all? no matter how you secure it, it will be sent back to server for decryption. Be be more specific, For authentication purpose, turn off session, i don't want to deal with session time out any more store some sort of id value in the cookie, on the server side, check if the id value exists and matches, if it is, authenticate user. let the cookie value expire when browser session is ended, this way. vs Asp.net form authentication mechanism (it relies on session or session id, i think) does latter one offer better security?

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• C# XNA: What can cause SpriteBatch.End() to throw a NRE?

  - by Rosarch

  I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm.... UPDATE 2: This does cause an NRE: protected override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.End(); // boned here //screenManager.Draw(gameTime); base.Draw(gameTime); }

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• Finding What You Need in R: function arguments/parameters from outside the function's package

  - by doug

  Often in R, there are a dozen functions scattered across as many packages--all of which have the same purpose but of course differ in accuracy, performance, theoretical rigor, and so on. How do you gather all of these in one place before you start your task? So for instance: the generic plot function. Setting secondary ticks is much easier (IMHO) using a function outside of the base package, minor.tick(nx=n, ny=n, tick.ratio=n), found in Hmisc. Of course, that doesn't show up in plot's docstring. Likewise, the data-input arguments to 'plot' can be supplied by an object returned from the function 'hexbin', again, from a library outside of the base installation (where 'plot' resides). What would be great obviously is a programmatic way to gather these function arguments from the various libraries and put them in a single namespace. edit: (trying to re-state my example just above more clearly:) the arguments to plot supplied in the base package for, e.g., setting the axis tick frequency are xaxp/yaxp; however, one can also set a/t/f via a function outside of the base package, again, as in the minor.tick function from the Hmisc package--but you wouldn't know that just from looking at the plot method signature. Is there a meta function in R for this? So far, as i come across them, i've been manually gathering them in a TextMate 'snippet' (along with the attendant library imports). This isn't that difficult or time consuming, but i can only update my snippet as i find out about these additional arguments/parameters. Is there a canonical R way to do this, or at least an easier way? Just in case that wasn't clear, i am not talking about the case where multiple packages provide functions directed to the same statistic or view (e.g., 'boxplot' in the base package; 'boxplot.matrix' in gplots; and 'bplots' in Rlab). What i am talking is the case in which the function name is the same across two or more packages.

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• Modules vs. Classes and their influence on descendants of ActiveRecord::Base

  - by Chris

  Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario: class Product < ActiveRecord::Base has_many(:prices) # define private helper methods end module PrintProduct attr_accessor(:isbn) # override methods in ActiveRecord::Base end class Book < Product include PrintProduct end Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior: After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found. Why is that? Book is a direct descendant of Product! More interesting is the following.. As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such: class Product < ActiveRecord::Base end class PrintProduct < Product end class Book < PrintProduct end All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module. Any insight would be appreciated. I'm dying to know why these errors are occurring!

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• How to post only a specific ASCX partial instead of the whole page

  - by Hallaghan

  I've got an ASPX page rendering a search ascx page which in turn will fill a grid on the main ASPX page. Aside that, I've also got an ascx page which uploads files, like this: <form method="post" action="<%= Url.Action("UploadFile") %>" enctype="multipart/form-data"> <fieldset> <input type="file" name="file" id="file" /> <%=Html.ButtonSubmit("Upload") %> </fieldset></form> Here's the problem: imagine I have searched for a single entry to be displayed on the grid. The grid displays this single entry and after wards, I upload a file and press the button "Upload". The whole page gets posted and the content in the grid is lost, now displaying all the results available. What could I do to prevent this from happening, maintaining the grid state (we're not using ViewState) or otherwise not posting back the whole page but only the ascx with the file upload? Note: I'm new to MVC.

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• Conversion failed when converting datetime from character string

  - by salvationishere

  I am developing a C# VS 2008 / SQL Server 2005 Express website application. I have tried some of the fixes for this problem but my call stack differs from others. And these fixes did not fix my problem. What steps can I take to troubleshoot this? Here is my error: System.Data.SqlClient.SqlException was caught Message="Conversion failed when converting datetime from character string." Source=".Net SqlClient Data Provider" ErrorCode=-2146232060 LineNumber=10 Number=241 Procedure="AppendDataCT" Server="\\\\.\\pipe\\772EF469-84F1-43\\tsql\\query" State=1 StackTrace: at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) at System.Data.SqlClient.SqlCommand.ExecuteNonQuery() at ADONET_namespace.ADONET_methods.AppendDataCT(DataTable dt, Dictionary`2 dic) in c:\Documents and Settings\Admin\My Documents\Visual Studio 2008\WebSites\Jerry\App_Code\ADONET methods.cs:line 102 And here is the related code. When I debugged this code, "dic" only looped through the 3 column names, but did not look into row values which are stored in "dt", the Data Table. public static string AppendDataCT(DataTable dt, Dictionary<string, string> dic) { if (dic.Count != 3) throw new ArgumentOutOfRangeException("dic can only have 3 parameters"); string connString = ConfigurationManager.ConnectionStrings["AW3_string"].ConnectionString; string errorMsg; try { using (SqlConnection conn2 = new SqlConnection(connString)) { using (SqlCommand cmd = conn2.CreateCommand()) { cmd.CommandText = "dbo.AppendDataCT"; cmd.CommandType = CommandType.StoredProcedure; cmd.Connection = conn2; foreach (string s in dic.Keys) { SqlParameter p = cmd.Parameters.AddWithValue(s, dic[s]); p.SqlDbType = SqlDbType.VarChar; } conn2.Open(); cmd.ExecuteNonQuery(); conn2.Close(); errorMsg = "The Person.ContactType table was successfully updated!"; } } }

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• In XSLT, how can you sort using an indirect key?

  - by edholder

  I am having trouble getting xsl:sort to understand the scope of the attributes I am referencing. Here is an XML sample document to illustrate: <Root> <DrinkSelections> <Drink id=1000 name="Coffee"/> <Drink id=1001 name="Water"/> <Drink id=1002 name="Tea"/> <Drink id=1003 name="Almost But Not Quite Entirely Unlike Tea"/> </DrinkSelections> <CustomerOrder> <Drinks> <Drink oid="1001"/> <Drink oid="1002"/> <Drink oid="1003"/> </Drinks> </CustomerOrder </Root> I want to produce a list of drinks (sorted by name) contained in the CustomerOrder. Here is the XSLT code I am fiddling with: <xsl:for-each select="/Root/CustomerOrder/Drinks/Drink"> <xsl:sort select="/Root/DrinkSelections/Drink[@id = @oid]/@name"/> <xsl:variable name=var_oid select="@oid"/> <xsl:value-of select="/Root/DrinkSelections/Drink[@id = $var_oid]/@name"/> </xsl:for-each> Apparently, the xsl:sort command is trying to apply the "oid" attribute to the Drink elements in DrinkSelections, rather than local Drink element. I can get around this using a variable, as in the xsl:value-of statement. But since xsl:sort must be the first statement after the xsl:for-each statement, I can't insert the xsl:variable statement before xsl:sort. Is there a way to explicitly state that the attribute value should be taken from the "local" element?

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• Communication between lexer and parser

  - by FredOverflow

  Every time I write a simple lexer and parser, I stumble upon the same question: how should the lexer and the parser communicate? I see four different approaches: The lexer eagerly converts the entire input string into a vector of tokens. Once this is done, the vector is fed to the parser which converts it into a tree. This is by far the simplest solution to implement, but since all tokens are stored in memory, it wastes a lot of space. Each time the lexer finds a token, it invokes a function on the parser, passing the current token. In my experience, this only works if the parser can naturally be implemented as a state machine like LALR parsers. By contrast, I don't think it would work at all for recursive descent parsers. Each time the parser needs a token, it asks the lexer for the next one. This is very easy to implement in C# due to the yield keyword, but quite hard in C++ which doesn't have it. The lexer and parser communicate through an asynchronous queue. This is commonly known under the title "producer/consumer", and it should simplify the communication between the lexer and the parser a lot. Does it also outperform the other solutions on multicores? Or is lexing too trivial? Is my analysis sound? Are there other approaches I haven't thought of? What is used in real-world compilers? It would be really cool if compiler writers like Eric Lippert could shed some light on this issue.

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• How to work with CTE. There is some error related to anchor.

  - by Shantanu Gupta

  I am creating a hierarchy representaion of a column. But an error occurs Details are Msg 240, Level 16, State 1, Line 1 Types don't match between the anchor and the recursive part in column "DISPLAY" of recursive query "CTE". I know there is some typecasting error. But I dont know how to remove error. Please just dont only sort out my error. I need explanation why this error is coming. When this error occurs. I am trying to sort table on the basis of sort col that i m introducing. I want to add '-' at every level and want to sort accordingly. Please help WITH CTE (PK_CATEGORY_ID, [DESCRIPTION], FK_CATEGORY_ID, DISPLAY, SORT, DEPTH) AS ( SELECT PK_CATEGORY_ID, [DESCRIPTION], FK_CATEGORY_ID, '-' AS DISPLAY, '--' AS SORT, 0 AS DEPTH FROM dbo.L_CATEGORY_TYPE WHERE FK_CATEGORY_ID IS NULL UNION ALL SELECT T.PK_CATEGORY_ID, T.[DESCRIPTION], T.FK_CATEGORY_ID, CAST(DISPLAY+T.[DESCRIPTION] AS VARCHAR(1000)), '--' AS SORT, C.DEPTH +1 FROM dbo.L_CATEGORY_TYPE T JOIN CTE C ON C.PK_CATEGORY_ID = T.FK_CATEGORY_ID --SELECT T.PK_CATEGORY_ID, C.SORT+T.[DESCRIPTION], T.FK_CATEGORY_ID --, CAST('--' + C.SORT AS VARCHAR(1000)) AS SORT, CAST(DEPTH +1 AS INT) AS DEPTH --FROM dbo.L_CATEGORY_TYPE T JOIN CTE C ON C.FK_CATEGORY_ID = T.PK_CATEGORY_ID ) SELECT PK_CATEGORY_ID, [DESCRIPTION], FK_CATEGORY_ID, DISPLAY, SORT, DEPTH FROM CTE ORDER BY SORT

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• How can I determine when an InnoDB table was last changed?

  - by David M

  I've had success in the past storing the (heavily) processed results of a database query in memcached, using the last update time of the underlying tables(s) as part of the cache key. For MyISAM tables, that last changed time is available in SHOW TABLE STATUS. Unfortunately, that's usually NULL for InnoDB tables. In MySQL 4.1, the ctime for an InnoDB in its SHOW TABLE STATUS line was usually its actual last update time, but that doesn't seem to be true for MySQL 5.1. There is a DATETIME field in the table, but it only shows when a row has been modified - it cannot show the deletion time of a row that's not there anymore! So, I really cannot use MAX(update_time). Here's the really tricky part. I have a number of replicas that I do reads from. Can I figure out the state of the table that doesn't rely on when the changes have actually been applied? My conclusion after working on this for a while is that it's not going to be possible to get this information as cheaply as I'd like. I'm probably going to cache data until the time that I expect the table to change (it's updated once a day), and let the query cache help out where it can.

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• How to write a "thread safe" function in C ?

  - by Andrei Ciobanu

  Hello I am writing some data structures in C, and I've realized that their associated functions aren't thread safe. The i am writing code uses only standard C, and I want to achieve some sort of 'synchronization'. I was thinking to do something like this: enum sync_e { TRUE, FALSE }; typedef enum sync_e sync; struct list_s { //Other stuff struct list_node_s *head; struct list_node_s *tail; enum sync_e locked; }; typedef struct list_s list; , to include a "boolean" field in the list structure that indicates the structures state: locked, unlocked. For example an insertion function will be rewritten this way: int list_insert_next(list* l, list_node *e, int x){ while(l->locked == TRUE){ /* Wait */ } l->locked = TRUE; /* Insert element */ /* -------------- */ l->locked = FALSE; return (0); } While operating on the list the 'locked' field will be set to TRUE, not allowing any other alterations. After operation completes the 'locked' field will be again set to 'TRUE'. Is this approach good ? Do you know other approaches (using only standard C).

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