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  • Knockout with ASP.Net MVC2 - HTML Extension Helpers for input controls

    - by Renso
    Goal: Defining Knockout-style input controls can be tedious and also may be something that you may find obtrusive, mixing your HTML with data bind syntax as well as binding your aspx, ascx files to Knockout. The goal is to make specifying Knockout specific HTML tags easy, seamless really, as well as being able to remove references to Knockout easily. Environment considerations: ASP.Net MVC2 or later Knockoutjs.js How to:     public static class HtmlExtensions     {         public static string DataBoundCheckBox(this HtmlHelper helper, string name, bool isChecked, object htmlAttributes)         {             var builder = new TagBuilder("input");             var dic = new RouteValueDictionary(htmlAttributes) { { "data-bind", String.Format("checked: {0}", name) } };             builder.MergeAttributes(dic);             builder.MergeAttribute("type", @"checkbox");             builder.MergeAttribute("name", name);             builder.MergeAttribute("value", @"true");             if (isChecked)             {                 builder.MergeAttribute("checked", @"checked");             }             return builder.ToString(TagRenderMode.SelfClosing);         }         public static MvcHtmlString DataBoundSelectList(this HtmlHelper helper, string name, IEnumerable<SelectListItem> selectList, String optionLabel)         {             var attrProperties = new StringBuilder();             attrProperties.Append(String.Format("optionsText: '{0}'", name));             if (!String.IsNullOrEmpty(optionLabel)) attrProperties.Append(String.Format(", optionsCaption: '{0}'", optionLabel));             attrProperties.Append(String.Format(", value: {0}", name));             var dic = new RouteValueDictionary { { "data-bind", attrProperties.ToString() } };             return helper.DropDownList(name, selectList, optionLabel, dic);         }         public static MvcHtmlString DataBoundSelectList(this HtmlHelper helper, string name, IEnumerable<SelectListItem> selectList, String optionLabel, object htmlAttributes)         {             var attrProperties = new StringBuilder();             attrProperties.Append(String.Format("optionsText: '{0}'", name));             if (!String.IsNullOrEmpty(optionLabel)) attrProperties.Append(String.Format(", optionsCaption: '{0}'", optionLabel));             attrProperties.Append(String.Format(", value: {0}", name));             var dic = new RouteValueDictionary(htmlAttributes) {{"data-bind", attrProperties}};             return helper.DropDownList(name, selectList, optionLabel, dic);         }         public static String DataBoundSelectList(this HtmlHelper helper, String options, String optionsText, String value)         {             return String.Format("<select data-bind=\"options: {0},optionsText: '{1}',value: {2}\"></select>", options, optionsText, value);         }         public static MvcHtmlString DataBoundTextBox(this HtmlHelper helper, string name, object value, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", name));             return helper.TextBox(name, value, dic);         }         public static MvcHtmlString DataBoundTextBox(this HtmlHelper helper, string name, string observable, object value, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", observable));             return helper.TextBox(name, value, dic);         }         public static MvcHtmlString DataBoundTextArea(this HtmlHelper helper, string name, string value, int rows, int columns, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", name));             return helper.TextArea(name, value, rows, columns, dic);         }         public static MvcHtmlString DataBoundTextArea(this HtmlHelper helper, string name, string observable, string value, int rows, int columns, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", observable));             return helper.TextArea(name, value, rows, columns, dic);         }         public static string BuildUrlFromExpression<T>(this HtmlHelper helper, Expression<Action<T>> action)         {             var values = CreateRouteValuesFromExpression(action);             var virtualPath = helper.RouteCollection.GetVirtualPath(helper.ViewContext.RequestContext, values);             if (virtualPath != null)             {                 return virtualPath.VirtualPath;             }             return null;         }         public static string ActionLink<T>(this HtmlHelper helper, Expression<Action<T>> action, string linkText)         {             return helper.ActionLink(action, linkText, null);         }         public static string ActionLink<T>(this HtmlHelper helper, Expression<Action<T>> action, string linkText, object htmlAttributes)         {             var values = CreateRouteValuesFromExpression(action);             var controllerName = (string)values["controller"];             var actionName = (string)values["action"];             values.Remove("controller");             values.Remove("action");             return helper.ActionLink(linkText, actionName, controllerName, values, new RouteValueDictionary(htmlAttributes)).ToHtmlString();         }         public static MvcForm Form<T>(this HtmlHelper helper, Expression<Action<T>> action)         {             return helper.Form(action, FormMethod.Post);         }         public static MvcForm Form<T>(this HtmlHelper helper, Expression<Action<T>> action, FormMethod method)         {             var values = CreateRouteValuesFromExpression(action);             string controllerName = (string)values["controller"];             string actionName = (string)values["action"];             values.Remove("controller");             values.Remove("action");             return helper.BeginForm(actionName, controllerName, values, method);         }         public static MvcForm Form<T>(this HtmlHelper helper, Expression<Action<T>> action, FormMethod method, object htmlAttributes)         {             var values = CreateRouteValuesFromExpression(action);             string controllerName = (string)values["controller"];             string actionName = (string)values["action"];             values.Remove("controller");             values.Remove("action");             return helper.BeginForm(actionName, controllerName, values, method, new RouteValueDictionary(htmlAttributes));         }         public static string VertCheckBox(this HtmlHelper helper, string name, bool isChecked)         {             return helper.CustomCheckBox(name, isChecked, null);         }          public static string CustomCheckBox(this HtmlHelper helper, string name, bool isChecked, object htmlAttributes)         {             TagBuilder builder = new TagBuilder("input");             builder.MergeAttributes(new RouteValueDictionary(htmlAttributes));             builder.MergeAttribute("type", "checkbox");             builder.MergeAttribute("name", name);             builder.MergeAttribute("value", "true");             if (isChecked)             {                 builder.MergeAttribute("checked", "checked");             }             return builder.ToString(TagRenderMode.SelfClosing);         }         public static string Script(this HtmlHelper helper, string script, object scriptAttributes)         {             var pathForCRMScripts = ScriptsController.GetPathForCRMScripts();             if (ScriptOptimizerConfig.EnableMinimizedFileLoad)             {                 string newPathForCRM = pathForCRMScripts + "Min/";                 ScriptsController.ServerPathMapper = new ServerPathMapper();                 string fullPath = ScriptsController.ServerMapPath(newPathForCRM);                 if (!File.Exists(fullPath + script))                     return null;                 if (!Directory.Exists(fullPath))                     return null;                 pathForCRMScripts = newPathForCRM;             }             var builder = new TagBuilder("script");             builder.MergeAttributes(new RouteValueDictionary(scriptAttributes));             builder.MergeAttribute("type", @"text/javascript");             builder.MergeAttribute("src", String.Format("{0}{1}", pathForCRMScripts.Replace("~", String.Empty), script));             return builder.ToString(TagRenderMode.SelfClosing);         }         private static RouteValueDictionary CreateRouteValuesFromExpression<T>(Expression<Action<T>> action)         {             if (action == null)                 throw new InvalidOperationException("Action must be provided");             var body = action.Body as MethodCallExpression;             if (body == null)             {                 throw new InvalidOperationException("Expression must be a method call");             }             if (body.Object != action.Parameters[0])             {                 throw new InvalidOperationException("Method call must target lambda argument");             }             // This will build up a RouteValueDictionary containing the controller name, action name, and any             // parameters passed as part of the "action" parameter.             string name = body.Method.Name;             string controllerName = typeof(T).Name;             if (controllerName.EndsWith("Controller", StringComparison.OrdinalIgnoreCase))             {                 controllerName = controllerName.Remove(controllerName.Length - 10, 10);             }             var values = BuildParameterValuesFromExpression(body) ?? new RouteValueDictionary();             values.Add("controller", controllerName);             values.Add("action", name);             return values;         }         private static RouteValueDictionary BuildParameterValuesFromExpression(MethodCallExpression call)         {             // Build up a RouteValueDictionary containing parameter names as keys and parameter values             // as values based on the MethodCallExpression passed in.             var values = new RouteValueDictionary();             ParameterInfo[] parameters = call.Method.GetParameters();             // If the passed in method has no parameters, just return an empty dictionary.             if (parameters.Length == 0)             {                 return values;             }             for (int i = 0; i < parameters.Length; i++)             {                 object parameterValue;                 Expression expression = call.Arguments[i];                 // If the current parameter is a constant, just use its value as the parameter value.                 var constant = expression as ConstantExpression;                 if (constant != null)                 {                     parameterValue = constant.Value;                 }                 else                 {                     // Otherwise, compile and execute the expression and use that as the parameter value.                     var function = Expression.Lambda<Func<object>>(Expression.Convert(expression, typeof(object)),                                                                    new ParameterExpression[0]);                     try                     {                         parameterValue = function.Compile()();                     }                     catch                     {                         parameterValue = null;                     }                 }                 values.Add(parameters[i].Name, parameterValue);             }             return values;         }     }   Some observations: The first two DataBoundSelectList overloaded methods are specifically built to load the data right into the drop down box as part of the HTML response stream rather than let Knockout's engine populate the options client-side. The third overloaded method does it client-side via the viewmodel. The first two overloads can be done when you have no requirement to add complex JSON objects to your lists. Furthermore, why render and parse the JSON object when you can have it all built and rendered server-side like any other list control.

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  • Tinkerforge Rotation/LCD & JavaFX Plans

    - by Geertjan
    The first time I integrated two Tinkerforge bricklets, the day before yesterday, was pretty cool: import com.tinkerforge.BrickMaster; import com.tinkerforge.BrickletLCD20x4; import com.tinkerforge.BrickletRotaryPoti; import com.tinkerforge.IPConnection; import java.util.Calendar; public class TFConnectionDemo { private static final String HOST = "localhost"; private static final int PORT = 4223; private static final String MASTERBRICKUID = "somethingabc"; private static final String LCDUID = "somethingabc"; private static final String ROTIUID = "somethingabc"; private static IPConnection ipc; private static BrickMaster master = new BrickMaster(MASTERBRICKUID); private static BrickletLCD20x4 lcd = new BrickletLCD20x4(LCDUID); private static BrickletRotaryPoti poti = new BrickletRotaryPoti(ROTIUID); public static void main(String[] args) { try { ipc = new IPConnection(HOST, PORT); ipc.addDevice(master); ipc.addDevice(lcd); ipc.addDevice(poti); poti.setPositionCallbackPeriod(50); poti.addListener(new BrickletRotaryPoti.PositionListener() { @Override public void position(short position) { lcd.clearDisplay(); Calendar cal = Calendar.getInstance(); lcd.writeLine((short) 0, (short) 0, cal.getTime().toString()); lcd.writeLine((short) 1, (short) 0, "Rotation: " + position); } }); } catch (Exception e) { } } } The result is that the display text in the LCD bricklet changes while I turn the rotation bricklet: Now imagine that you have some JavaFX charts and, while you turn the rotation bricklet (i.e., the dial thing that I'm turning above), the values of the charts change. That would be pretty cool because you'd be able to animate the JavaFX charts by rotating an object externally, i.e., without even touching the keyboard. That would be pretty cool to see and shouldn't be hard to implement.

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  • Java Grade Calculator program for class kepp geting the error "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." [migrated]

    - by user2880621
    this is my first question I've posted. I've used this site to look at other questions to help with similar problems I've had. After some cursory looking I couldn't find quite the answer I was looking for so I decided to finally succumb and create an account. I am fairly new to java, only a few weeks into my first class. Anyway, my project is to create a program which takes any amount of students and their grades, and then assign them a letter grade. The catch is, however, that it is on a sort of curve and the other grades' letter are dependent on the the highest. Anything equal to or 10 points below the best grade is an a, anything 11-20 points below is a b, and so on. I am to use an array, but I get this error when ran "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." I will go ahead and post my code down below. Thanks for any advice you may be able to give. package grade.calculator; import java.util.Scanner; /** * * @author nichol57 */ public class GradeCalculator { /** * @param args the command line arguments */ public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println("Enter the number of students"); int number = input.nextInt(); double[]grades = new double [number]; for (int J = number; J >=0; J--) { System.out.println("Enter the students' grades"); grades[J] = input.nextDouble(); } double best = grades[0]; for (int J = 1; J < number; J++) { if (grades[J] >= best){ best = grades[J]; } } for (int J = 0;J < number; J++){ if (grades[J] >= best - 10){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "A"); } else if (grades[J] >= best - 20){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "B"); } else if (grades[J] >= best - 30) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "C"); } else if (grades[J] >= best - 40) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "D"); } else { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "F"); } } // end for loop for output }// end main method }

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  • DB Object passing between classes singleton, static or other?

    - by Stephen
    So I'm designing a reporting system at work it's my first project written OOP and I'm stuck on the design choice for the DB class. Obviously I only want to create one instance of the DB class per-session/user and then pass it to each of the classes that need it. What I don't know it what's best practice for implementing this. Currently I have code like the following:- class db { private $user = 'USER'; private $pass = 'PASS'; private $tables = array( 'user','report', 'etc...'); function __construct(){ //SET UP CONNECTION AND TABLES } }; class report{ function __construct ($params = array(), $db, $user) { //Error checking/handling trimed //$db is the database object we created $this->db = $db; //$this->user is the user object for the logged in user $this->user = $user; $this->reportCreate(); } public function setPermission($permissionId = 1) { //Note the $this->db is this the best practise solution? $this->db->permission->find($permissionId) //Note the $this->user is this the best practise solution? $this->user->checkPermission(1) $data=array(); $this->db->reportpermission->insert($data) } };//end report I've been reading about using static classes and have just come across Singletons (though these appear to be passé already?) so what's current best practice for doing this?

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  • Website migration from WordPress to a static site and doing 301 redirects without access to existing site?

    - by user3114468
    Currently working on a project that is a hosted on WordPress that is being migrated to a static site. However I presently do not have access to the existing site as it's managed by another developer. The concern is not the lack of having access to content as the site owner has generated very little content (reason for migration) and we were able to do this manually. Rather the concern is to do 301 redirects. The site will not change domains but URLs such as from example.com/?page_id=3 to example.com/services. To add, the site is migrating to new server using same domain name. I thought maybe this could be done via editing permalinks prior to migration and WordPress would update automatically if configured to write on server. But if not configured (as this is not always the case) I do not have htaccess to fix it in case there are suddenly a bunch of 404 errors for every page. Really could use some help on the best procedure to follow in this case. This is the first migration project I've worked on.

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  • jqGrid: sort by index

    - by David__
    I am having trouble getting a column to sort by an index other than the 'name' value. In this case I am trying to sort the aggregation type column (values are days of the week) by the week order, rather than alphanumeric order. To do this I added an index column ('Aggregation type-index') that has the days of week an integers. However with this configuration, it fails to sort that column by index or name. Can someone point me the err in my ways? I posted all the js and css that is on the page, because I am also having two other issues, that if you notice the problem great, otherwise I'll keep hunting. I want to be able to enable the column reodering and be able to resize the grid (Both shown at http://trirand.com/blog/jqgrid/jqgrid.html under the new in 3.6 tab). Both options are not working either. <link rel="stylesheet" type="text/css" href="/static/latest_ui/themes/base/jquery.ui.all.css"/> <link rel="stylesheet" type="text/css" media="print" href="/static/css/print.css"/> <script src="/static/js/jquery-1.7.2.min.js" type="text/javascript"></script> <script src="/static/latest_ui/ui/jquery.ui.core.js"></script> <script src="/static/latest_ui/ui/jquery.ui.widget.js"></script> <script src="/static/latest_ui/ui/jquery.ui.position.js"></script> <script src="/static/latest_ui/ui/jquery.ui.button.js"></script> <script src="/static/latest_ui/ui/jquery.ui.menu.js"></script> <script src="/static/latest_ui/ui/jquery.ui.menubar.js"></script> <script src="/static/latest_ui/ui/jquery.ui.tabs.js"></script> <script src="/static/latest_ui/ui/jquery.ui.datepicker.js"></script> <script src="/static/js/custom.js"></script> <link rel="stylesheet" type="text/css" media="all" href="/static/css/custom_style.css" /> <link rel="stylesheet" type="text/css" media="all" href="/static/css/custom_colors.css" /> <link rel="stylesheet" type="text/css" media="screen" href="/static/css/ui.jqgrid.css" /> <body> <table id="grid_reports"></table> <div id='pager'></div> </body> <script src="/static/latest_ui/ui/jquery.ui.resizable.js"></script> <script src="/static/latest_ui/ui/jquery.ui.sortable.js"></script> <script src="/static/js/grid.locale-en.js" type="text/javascript"></script> <script src="/static/js/jquery.jqGrid.min.js" type="text/javascript"></script> <script src="/static/js/jqGrid_src/grid.jqueryui.js"></script> <script> $(function() { jQuery("#grid_reports").jqGrid({ sortable: true, datatype: "local", height: 500, width: 300, colNames:['Series', 'Agg Type', 'Days'], colModel:[{'index': 'By series', 'align': 'left', 'sorttype': 'text', 'name': 'By series', 'width': 65}, {'index': 'Aggregation type-index', 'align': 'left', 'sorttype': 'int', 'name': 'Aggregation type', 'width': 75}, {'index': 'Days since event', 'align': 'center', 'sorttype': 'text', 'name': 'Days since event', 'width': 50}], rowNum:50, pager: '#pager', sortname: 'Aggregation type', sortorder: 'desc', altRows: true, rowList:[20,50,100,500,10000], viewrecords: true, gridview: true, caption: "Report for 6/19/12" }); jQuery("#grid_reports").navGrid("#pager",{edit:false,add:false,del:false}); jQuery("#grid_reports").jqGrid('gridResize',{minWidth:60,maxWidth:2500,minHeight:80, maxHeight:2500}); var mydata = [{'Days since event': 132, 'Aggregation type': 'Date=Fri', 'By series': 'mean', 'Aggregation type-index': 5}, {'DIM at event': 178, 'Aggregation type': 'Date=Thu', 'By series': 'mean', 'Aggregation type-index': 4}, {'DIM at event': 172, 'Aggregation type': 'Date=Wed', 'By series': 'mean', 'Aggregation type-index': 3}, {'DIM at event': 146, 'Aggregation type': 'Date=Tue', 'By series': 'mean', 'Aggregation type-index': 2}, {'DIM at event': 132, 'Aggregation type': 'Date=Sat', 'By series': 'mean', 'Aggregation type-index': 6}, {'DIM at event': 162, 'Aggregation type': 'Date=Mon', 'By series': 'mean', 'Aggregation type-index': 1}, {'DIM at event': 139, 'Aggregation type': 'Date=Sun', 'By series': 'mean', 'Aggregation type-index': 0}]; for(var i=0;i<=mydata.length;i++) jQuery("#grid_reports").jqGrid('addRowData',i+1,mydata[i]); }); </script>

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  • How to setup a static multicast ARP entry with Cisco SG300?

    - by Fredrik Hedberg
    We're running a Microsoft NLB cluster in multicast mode as a loadbalancer. Using our old Cisco IOS switches we propagate access to the cluster to our branches using a static ARP entry in the core router: arp 10.20.1.226 03bf.0a14.01e2 ARPA But how does one solve this using non-IOS based Cisco hardware such as the SG300 series? Adding a static ARP entry results in an error message telling the user that the hardware address needs to be a valid unicast MAC address.

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  • Static IP on Wifi at work and dynamic at home?

    - by Jason Shultz
    I need the laptops at my office to have a static IP for security purposes and identification. However, some employees take their laptops home in the evening. If I have the wifi config set to use a static IP, how can they have a dynamic IP at home? the laptops are using Windows Vista and Windows 7.

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  • Static IP on Wi-Fi at work and dynamic at home?

    - by Jason Shultz
    I need the laptops at my office to have a static IP for security purposes and identification. However, some employees take their laptops home in the evening. If I have the Wi-Fi configuration set to use a static IP, how can they have a dynamic IP at home? The laptops are using Windows Vista and Windows 7.

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  • Static IP address on Wi-Fi at work and dynamic at home?

    - by Jason Shultz
    I need the laptops at my office to have a static IP address for security purposes and identification. However, some employees take their laptops home in the evening. If I have the Wi-Fi configuration set to use a static IP address, how can they have a dynamic IP address at home? The laptops are using Windows Vista and Windows 7.

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  • Need some help on how to replay the last game of a java maze game

    - by Marty
    Hello, I am working on creating a Java maze game for a project. The maze is displayed on the console as standard output not in an applet. I have created most of hte code I need, however I am stuck at one problem and that is I need a user to be able to replay the last game i.e redraw the maze with the users moves but without any input from the user. I am not sure on what course of action to take, i was thinking about copying each users move or the position of each move into another array, as you can see i have 2 variables which hold the position of the player, plyrX and plyrY do you think copying these values into a new array after each move would solve my problem and how would i go about this? I have updated my code, apologies about the textIO.java class not being present, not sure how to resolve that exept post a link to TextIO.java [TextIO.java][1] My code below is updated with a new array of type char to hold values from the original maze (read in from text file and displayed using unicode characters) and also to new variables c_plyrX and c_plyrY which I am thinking should hold the values of plyrX and plyrY and copy them into the new array. When I try to call the replayGame(); method from the menu the maze loads for a second then the console exits so im not sure what I am doing wrong Thanks public class MazeGame { //unicode characters that will define the maze walls, //pathways, and in game characters. final static char WALL = '\u2588'; //wall final static char PATH = '\u2591'; //pathway final static char PLAYER = '\u25EF'; //player final static char ENTRANCE = 'E'; //entrance final static char EXIT = '\u2716'; //exit //declaring member variables which will hold the maze co-ordinates //X = rows, Y = columns static int entX = 0; //entrance X co-ordinate static int entY = 1; //entrance y co-ordinate static int plyrX = 0; static int plyrY = 1; static int exitX = 24; //exit X co-ordinate static int exitY = 37; //exit Y co-ordinate //static member variables which hold maze values //used so values can be accessed from different methods static int rows; //rows variable static int cols; //columns variable static char[][] maze; //defines 2 dimensional array to hold the maze //variables that hold player movement values static char dir; //direction static int spaces; //amount of spaces user can travel //variable to hold amount of moves the user has taken; static int movesTaken = 0; //new array to hold player moves for replaying game static char[][] mazeCopy; static int c_plyrX; static int c_plyrY; /** userMenu method for displaying the user menu which will provide various options for * the user to choose such as play a maze game, get instructions, etc. */ public static void userMenu(){ TextIO.putln("Maze Game"); TextIO.putln("*********"); TextIO.putln("Choose an option."); TextIO.putln(""); TextIO.putln("1. Play the Maze Game."); TextIO.putln("2. View Instructions."); TextIO.putln("3. Replay the last game."); TextIO.putln("4. Exit the Maze Game."); TextIO.putln(""); int option; //variable for holding users option TextIO.put("Type your choice: "); option = TextIO.getlnInt(); //gets users option //switch statement for processing menu options switch(option){ case 1: playMazeGame(); case 2: instructions(); case 3: if (c_plyrX == plyrX && c_plyrY == plyrY)replayGame(); else { TextIO.putln("Option not available yet, you need to play a game first."); TextIO.putln(); userMenu(); } case 4: System.exit(0); //exits the user out of the console default: TextIO.put("Option must be 1, 2, 3 or 4"); } } //end of userMenu /**main method, will call the userMenu and get the users choice and call * the relevant method to execute the users choice. */ public static void main(String[]args){ userMenu(); //calls the userMenu method } //end of main method /**instructions method, displays instructions on how to play * the game to the user/ */ public static void instructions(){ TextIO.putln("To beat the Maze Game you have to move your character"); TextIO.putln("through the maze and reach the exit in as few moves as possible."); TextIO.putln(""); TextIO.putln("Your characer is displayed as a " + PLAYER); TextIO.putln("The maze exit is displayed as a " + EXIT); TextIO.putln("Reach the exit and you have won escaped the maze."); TextIO.putln("To control your character type the direction you want to go"); TextIO.putln("and how many spaces you want to move"); TextIO.putln("for example 'D3' will move your character"); TextIO.putln("down 3 spaces."); TextIO.putln("Remember you can't walk through walls!"); boolean insOption; //boolean variable TextIO.putln(""); TextIO.put("Do you want to play the Maze Game now? (Y or N) "); insOption = TextIO.getlnBoolean(); if (insOption == true)playMazeGame(); else userMenu(); } //end of instructions method /**playMazeGame method, calls the loadMaze method and the charMove method * to start playing the Maze Game. */ public static void playMazeGame(){ loadMaze(); plyrMoves(); } //end of playMazeGame method /**loadMaze method, loads the 39x25 maze from the MazeGame.txt text file * and inserts values from the text file into the maze array and * displays the maze on screen using the unicode block characters. * plyrX and plyrY variables are set at their staring co ordinates so that when * a game is completed and the user selects to play a new game * the player character will always be at position 01. */ public static void loadMaze(){ plyrX = 0; plyrY = 1; TextIO.readFile("MazeGame.txt"); //now reads from the external MazeGame.txt file rows = TextIO.getInt(); //gets the number of rows from text file to create X dimensions cols = TextIO.getlnInt(); //gets number of columns from text file to create Y dimensions maze = new char[rows][cols]; //creates maze array of base type char with specified dimnensions //loop to process the array and read in values from the text file. for (int i = 0; i<rows; i++){ for (int j = 0; j<cols; j++){ maze[i][j] = TextIO.getChar(); } TextIO.getln(); } //end for loop TextIO.readStandardInput(); //closes MazeGame.txt file and reads from //standard input. //loop to process the array values and display as unicode characters for (int i = 0; i<rows; i++){ for (int j = 0; j<cols; j++){ if (i == plyrX && j == plyrY){ plyrX = i; plyrY = j; TextIO.put(PLAYER); //puts the player character at player co-ords } else{ if (maze[i][j] == '0') TextIO.putf("%c",WALL); //puts wall block if (maze[i][j] == '1') TextIO.putf("%c",PATH); //puts path block if (maze[i][j] == '2') { entX = i; entY = j; TextIO.putf("%c",ENTRANCE); //puts entrance character } if (maze[i][j] == '3') { exitX = i; //holds value of exit exitY = j; //co-ordinates TextIO.putf("%c",EXIT); //puts exit character } } } TextIO.putln(); } //end for loop } //end of loadMaze method /**redrawMaze method, method for redrawing the maze after each move. * */ public static void redrawMaze(){ TextIO.readFile("MazeGame.txt"); //now reads from the external MazeGame.txt file rows = TextIO.getInt(); //gets the number of rows from text file to create X dimensions cols = TextIO.getlnInt(); //gets number of columns from text file to create Y dimensions maze = new char[rows][cols]; //creates maze array of base type char with specified dimnensions //loop to process the array and read in values from the text file. for (int i = 0; i<rows; i++){ for (int j = 0; j<cols; j++){ maze[i][j] = TextIO.getChar(); } TextIO.getln(); } //end for loop TextIO.readStandardInput(); //closes MazeGame.txt file and reads from //standard input. //loop to process the array values and display as unicode characters for (int i = 0; i<rows; i++){ for (int j = 0; j<cols; j++){ if (i == plyrX && j == plyrY){ plyrX = i; plyrY = j; TextIO.put(PLAYER); //puts the player character at player co-ords } else{ if (maze[i][j] == '0') TextIO.putf("%c",WALL); //puts wall block if (maze[i][j] == '1') TextIO.putf("%c",PATH); //puts path block if (maze[i][j] == '2') { entX = i; entY = j; TextIO.putf("%c",ENTRANCE); //puts entrance character } if (maze[i][j] == '3') { exitX = i; //holds value of exit exitY = j; //co-ordinates TextIO.putf("%c",EXIT); //puts exit character } } } TextIO.putln(); } //end for loop } //end redrawMaze method /**replay game method * */ public static void replayGame(){ c_plyrX = plyrX; c_plyrY = plyrY; TextIO.readFile("MazeGame.txt"); //now reads from the external MazeGame.txt file rows = TextIO.getInt(); //gets the number of rows from text file to create X dimensions cols = TextIO.getlnInt(); //gets number of columns from text file to create Y dimensions mazeCopy = new char[rows][cols]; //creates maze array of base type char with specified dimnensions //loop to process the array and read in values from the text file. for (int i = 0; i<rows; i++){ for (int j = 0; j<cols; j++){ mazeCopy[i][j] = TextIO.getChar(); } TextIO.getln(); } //end for loop TextIO.readStandardInput(); //closes MazeGame.txt file and reads from //standard input. //loop to process the array values and display as unicode characters for (int i = 0; i<rows; i++){ for (int j = 0; j<cols; j++){ if (i == c_plyrX && j == c_plyrY){ c_plyrX = i; c_plyrY = j; TextIO.put(PLAYER); //puts the player character at player co-ords } else{ if (mazeCopy[i][j] == '0') TextIO.putf("%c",WALL); //puts wall block if (mazeCopy[i][j] == '1') TextIO.putf("%c",PATH); //puts path block if (mazeCopy[i][j] == '2') { entX = i; entY = j; TextIO.putf("%c",ENTRANCE); //puts entrance character } if (mazeCopy[i][j] == '3') { exitX = i; //holds value of exit exitY = j; //co-ordinates TextIO.putf("%c",EXIT); //puts exit character } } } TextIO.putln(); } //end for loop } //end replayGame method /**plyrMoves method, method for moving the players character * around the maze. */ public static void plyrMoves(){ int nplyrX = plyrX; int nplyrY = plyrY; int pMoves; direction(); //UP if (dir == 'U' || dir == 'u'){ nplyrX = plyrX; nplyrY = plyrY; for(pMoves = 0; pMoves <= spaces; pMoves++){ if (maze[nplyrX][nplyrY] == '0'){ TextIO.putln("Invalid move, try again."); } else if (pMoves != spaces){ nplyrX =plyrX + 1; } else { plyrX = plyrX-spaces; c_plyrX = plyrX; movesTaken++; } } }//end UP if //DOWN if (dir == 'D' || dir == 'd'){ nplyrX = plyrX; nplyrY = plyrY; for (pMoves = 0; pMoves <= spaces; pMoves ++){ if (maze[nplyrX][nplyrY] == '0'){ TextIO.putln("Invalid move, try again"); } else if (pMoves != spaces){ nplyrX = plyrX+1; } else{ plyrX = plyrX+spaces; c_plyrX = plyrX; movesTaken++; } } } //end DOWN if //LEFT if (dir == 'L' || dir =='l'){ nplyrX = plyrX; nplyrY = plyrY; for (pMoves = 0; pMoves <= spaces; pMoves++){ if (maze[nplyrX][nplyrY] == '0'){ TextIO.putln("Invalid move, try again"); } else if (pMoves != spaces){ nplyrY = plyrY + 1; } else{ plyrY = plyrY-spaces; c_plyrY = plyrY; movesTaken++; } } } //end LEFT if //RIGHT if (dir == 'R' || dir == 'r'){ nplyrX = plyrX; nplyrY = plyrY; for (pMoves = 0; pMoves <= spaces; pMoves++){ if (maze[nplyrX][nplyrY] == '0'){ TextIO.putln("Invalid move, try again."); } else if (pMoves != spaces){ nplyrY += 1; } else{ plyrY = plyrY+spaces; c_plyrY = plyrY; movesTaken++; } } } //end RIGHT if //prints message if player escapes from the maze. if (maze[plyrX][plyrY] == '3'){ TextIO.putln("****Congratulations****"); TextIO.putln(); TextIO.putln("You have escaped from the maze."); TextIO.putln(); userMenu(); } else{ movesTaken++; redrawMaze(); plyrMoves(); } } //end of plyrMoves method /**direction, method * */ public static char direction(){ TextIO.putln("Enter the direction you wish to move in and the distance"); TextIO.putln("i.e D3 = move down 3 spaces"); TextIO.putln("U - Up, D - Down, L - Left, R - Right: "); dir = TextIO.getChar(); if (dir =='U' || dir == 'D' || dir == 'L' || dir == 'R' || dir == 'u' || dir == 'd' || dir == 'l' || dir == 'r'){ spacesMoved(); } else{ loadMaze(); TextIO.putln("Invalid direction!"); TextIO.put("Direction must be one of U, D, L or R"); direction(); } return dir; //returns the value of dir (direction) } //end direction method /**spaces method, gets the amount of spaces the user wants to move * */ public static int spacesMoved(){ TextIO.putln(" "); spaces = TextIO.getlnInt(); if (spaces <= 0){ loadMaze(); TextIO.put("Invalid amount of spaces, try again"); spacesMoved(); } return spaces; } //end spacesMoved method } //end of MazeGame class

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  • C#/.NET Little Wonders: ConcurrentBag and BlockingCollection

    - by James Michael Hare
    In the first week of concurrent collections, began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>.  The last post discussed the ConcurrentDictionary<T> .  Finally this week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see C#/.NET Little Wonders: A Redux. Recap As you'll recall from the previous posts, the original collections were object-based containers that accomplished synchronization through a Synchronized member.  With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization.  With .NET 4.0, a new breed of collections was born in the System.Collections.Concurrent namespace.  Of these, the final concurrent collection we will examine is the ConcurrentBag and a very useful wrapper class called the BlockingCollection. For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this informative whitepaper by the Microsoft Parallel Computing Platform team here. ConcurrentBag<T> – Thread-safe unordered collection. Unlike the other concurrent collections, the ConcurrentBag<T> has no non-concurrent counterpart in the .NET collections libraries.  Items can be added and removed from a bag just like any other collection, but unlike the other collections, the items are not maintained in any order.  This makes the bag handy for those cases when all you care about is that the data be consumed eventually, without regard for order of consumption or even fairness – that is, it’s possible new items could be consumed before older items given the right circumstances for a period of time. So why would you ever want a container that can be unfair?  Well, to look at it another way, you can use a ConcurrentQueue and get the fairness, but it comes at a cost in that the ordering rules and synchronization required to maintain that ordering can affect scalability a bit.  Thus sometimes the bag is great when you want the fastest way to get the next item to process, and don’t care what item it is or how long its been waiting. The way that the ConcurrentBag works is to take advantage of the new ThreadLocal<T> type (new in System.Threading for .NET 4.0) so that each thread using the bag has a list local to just that thread.  This means that adding or removing to a thread-local list requires very low synchronization.  The problem comes in where a thread goes to consume an item but it’s local list is empty.  In this case the bag performs “work-stealing” where it will rob an item from another thread that has items in its list.  This requires a higher level of synchronization which adds a bit of overhead to the take operation. So, as you can imagine, this makes the ConcurrentBag good for situations where each thread both produces and consumes items from the bag, but it would be less-than-idea in situations where some threads are dedicated producers and the other threads are dedicated consumers because the work-stealing synchronization would outweigh the thread-local optimization for a thread taking its own items. Like the other concurrent collections, there are some curiosities to keep in mind: IsEmpty(), Count, ToArray(), and GetEnumerator() lock collection Each of these needs to take a snapshot of whole bag to determine if empty, thus they tend to be more expensive and cause Add() and Take() operations to block. ToArray() and GetEnumerator() are static snapshots Because it is based on a snapshot, will not show subsequent updates after snapshot. Add() is lightweight Since adding to the thread-local list, there is very little overhead on Add. TryTake() is lightweight if items in thread-local list As long as items are in the thread-local list, TryTake() is very lightweight, much more so than ConcurrentStack() and ConcurrentQueue(), however if the local thread list is empty, it must steal work from another thread, which is more expensive. Remember, a bag is not ideal for all situations, it is mainly ideal for situations where a process consumes an item and either decomposes it into more items to be processed, or handles the item partially and places it back to be processed again until some point when it will complete.  The main point is that the bag works best when each thread both takes and adds items. For example, we could create a totally contrived example where perhaps we want to see the largest power of a number before it crosses a certain threshold.  Yes, obviously we could easily do this with a log function, but bare with me while I use this contrived example for simplicity. So let’s say we have a work function that will take a Tuple out of a bag, this Tuple will contain two ints.  The first int is the original number, and the second int is the last multiple of that number.  So we could load our bag with the initial values (let’s say we want to know the last multiple of each of 2, 3, 5, and 7 under 100. 1: var bag = new ConcurrentBag<Tuple<int, int>> 2: { 3: Tuple.Create(2, 1), 4: Tuple.Create(3, 1), 5: Tuple.Create(5, 1), 6: Tuple.Create(7, 1) 7: }; Then we can create a method that given the bag, will take out an item, apply the multiplier again, 1: public static void FindHighestPowerUnder(ConcurrentBag<Tuple<int,int>> bag, int threshold) 2: { 3: Tuple<int,int> pair; 4:  5: // while there are items to take, this will prefer local first, then steal if no local 6: while (bag.TryTake(out pair)) 7: { 8: // look at next power 9: var result = Math.Pow(pair.Item1, pair.Item2 + 1); 10:  11: if (result < threshold) 12: { 13: // if smaller than threshold bump power by 1 14: bag.Add(Tuple.Create(pair.Item1, pair.Item2 + 1)); 15: } 16: else 17: { 18: // otherwise, we're done 19: Console.WriteLine("Highest power of {0} under {3} is {0}^{1} = {2}.", 20: pair.Item1, pair.Item2, Math.Pow(pair.Item1, pair.Item2), threshold); 21: } 22: } 23: } Now that we have this, we can load up this method as an Action into our Tasks and run it: 1: // create array of tasks, start all, wait for all 2: var tasks = new[] 3: { 4: new Task(() => FindHighestPowerUnder(bag, 100)), 5: new Task(() => FindHighestPowerUnder(bag, 100)), 6: }; 7:  8: Array.ForEach(tasks, t => t.Start()); 9:  10: Task.WaitAll(tasks); Totally contrived, I know, but keep in mind the main point!  When you have a thread or task that operates on an item, and then puts it back for further consumption – or decomposes an item into further sub-items to be processed – you should consider a ConcurrentBag as the thread-local lists will allow for quick processing.  However, if you need ordering or if your processes are dedicated producers or consumers, this collection is not ideal.  As with anything, you should performance test as your mileage will vary depending on your situation! BlockingCollection<T> – A producers & consumers pattern collection The BlockingCollection<T> can be treated like a collection in its own right, but in reality it adds a producers and consumers paradigm to any collection that implements the interface IProducerConsumerCollection<T>.  If you don’t specify one at the time of construction, it will use a ConcurrentQueue<T> as its underlying store. If you don’t want to use the ConcurrentQueue, the ConcurrentStack and ConcurrentBag also implement the interface (though ConcurrentDictionary does not).  In addition, you are of course free to create your own implementation of the interface. So, for those who don’t remember the producers and consumers classical computer-science problem, the gist of it is that you have one (or more) processes that are creating items (producers) and one (or more) processes that are consuming these items (consumers).  Now, the crux of the problem is that there is a bin (queue) where the produced items are placed, and typically that bin has a limited size.  Thus if a producer creates an item, but there is no space to store it, it must wait until an item is consumed.  Also if a consumer goes to consume an item and none exists, it must wait until an item is produced. The BlockingCollection makes it trivial to implement any standard producers/consumers process set by providing that “bin” where the items can be produced into and consumed from with the appropriate blocking operations.  In addition, you can specify whether the bin should have a limited size or can be (theoretically) unbounded, and you can specify timeouts on the blocking operations. As far as your choice of “bin”, for the most part the ConcurrentQueue is the right choice because it is fairly light and maximizes fairness by ordering items so that they are consumed in the same order they are produced.  You can use the concurrent bag or stack, of course, but your ordering would be random-ish in the case of the former and LIFO in the case of the latter. So let’s look at some of the methods of note in BlockingCollection: BoundedCapacity returns capacity of the “bin” If the bin is unbounded, the capacity is int.MaxValue. Count returns an internally-kept count of items This makes it O(1), but if you modify underlying collection directly (not recommended) it is unreliable. CompleteAdding() is used to cut off further adds. This sets IsAddingCompleted and begins to wind down consumers once empty. IsAddingCompleted is true when producers are “done”. Once you are done producing, should complete the add process to alert consumers. IsCompleted is true when producers are “done” and “bin” is empty. Once you mark the producers done, and all items removed, this will be true. Add() is a blocking add to collection. If bin is full, will wait till space frees up Take() is a blocking remove from collection. If bin is empty, will wait until item is produced or adding is completed. GetConsumingEnumerable() is used to iterate and consume items. Unlike the standard enumerator, this one consumes the items instead of iteration. TryAdd() attempts add but does not block completely If adding would block, returns false instead, can specify TimeSpan to wait before stopping. TryTake() attempts to take but does not block completely Like TryAdd(), if taking would block, returns false instead, can specify TimeSpan to wait. Note the use of CompleteAdding() to signal the BlockingCollection that nothing else should be added.  This means that any attempts to TryAdd() or Add() after marked completed will throw an InvalidOperationException.  In addition, once adding is complete you can still continue to TryTake() and Take() until the bin is empty, and then Take() will throw the InvalidOperationException and TryTake() will return false. So let’s create a simple program to try this out.  Let’s say that you have one process that will be producing items, but a slower consumer process that handles them.  This gives us a chance to peek inside what happens when the bin is bounded (by default, the bin is NOT bounded). 1: var bin = new BlockingCollection<int>(5); Now, we create a method to produce items: 1: public static void ProduceItems(BlockingCollection<int> bin, int numToProduce) 2: { 3: for (int i = 0; i < numToProduce; i++) 4: { 5: // try for 10 ms to add an item 6: while (!bin.TryAdd(i, TimeSpan.FromMilliseconds(10))) 7: { 8: Console.WriteLine("Bin is full, retrying..."); 9: } 10: } 11:  12: // once done producing, call CompleteAdding() 13: Console.WriteLine("Adding is completed."); 14: bin.CompleteAdding(); 15: } And one to consume them: 1: public static void ConsumeItems(BlockingCollection<int> bin) 2: { 3: // This will only be true if CompleteAdding() was called AND the bin is empty. 4: while (!bin.IsCompleted) 5: { 6: int item; 7:  8: if (!bin.TryTake(out item, TimeSpan.FromMilliseconds(10))) 9: { 10: Console.WriteLine("Bin is empty, retrying..."); 11: } 12: else 13: { 14: Console.WriteLine("Consuming item {0}.", item); 15: Thread.Sleep(TimeSpan.FromMilliseconds(20)); 16: } 17: } 18: } Then we can fire them off: 1: // create one producer and two consumers 2: var tasks = new[] 3: { 4: new Task(() => ProduceItems(bin, 20)), 5: new Task(() => ConsumeItems(bin)), 6: new Task(() => ConsumeItems(bin)), 7: }; 8:  9: Array.ForEach(tasks, t => t.Start()); 10:  11: Task.WaitAll(tasks); Notice that the producer is faster than the consumer, thus it should be hitting a full bin often and displaying the message after it times out on TryAdd(). 1: Consuming item 0. 2: Consuming item 1. 3: Bin is full, retrying... 4: Bin is full, retrying... 5: Consuming item 3. 6: Consuming item 2. 7: Bin is full, retrying... 8: Consuming item 4. 9: Consuming item 5. 10: Bin is full, retrying... 11: Consuming item 6. 12: Consuming item 7. 13: Bin is full, retrying... 14: Consuming item 8. 15: Consuming item 9. 16: Bin is full, retrying... 17: Consuming item 10. 18: Consuming item 11. 19: Bin is full, retrying... 20: Consuming item 12. 21: Consuming item 13. 22: Bin is full, retrying... 23: Bin is full, retrying... 24: Consuming item 14. 25: Adding is completed. 26: Consuming item 15. 27: Consuming item 16. 28: Consuming item 17. 29: Consuming item 19. 30: Consuming item 18. Also notice that once CompleteAdding() is called and the bin is empty, the IsCompleted property returns true, and the consumers will exit. Summary The ConcurrentBag is an interesting collection that can be used to optimize concurrency scenarios where tasks or threads both produce and consume items.  In this way, it will choose to consume its own work if available, and then steal if not.  However, in situations where you want fair consumption or ordering, or in situations where the producers and consumers are distinct processes, the bag is not optimal. The BlockingCollection is a great wrapper around all of the concurrent queue, stack, and bag that allows you to add producer and consumer semantics easily including waiting when the bin is full or empty. That’s the end of my dive into the concurrent collections.  I’d also strongly recommend, once again, you read this excellent Microsoft white paper that goes into much greater detail on the efficiencies you can gain using these collections judiciously (here). Tweet Technorati Tags: C#,.NET,Concurrent Collections,Little Wonders

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  • Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

    - by Rowan Freeman
    Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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  • C# Lack of Static Inheritance - What Should I Do?

    - by yellowblood
    Alright, so as you probably know, static inheritance is impossible in C#. I understand that, however I'm stuck with the development of my program. I will try to make it as simple as possible. Lets say our code needs to manage objects that are presenting aircrafts in some airport. The requirements are as follows: There are members and methods that are shared for all aircrafts There are many types of aircrafts, each type may have its own extra methods and members. There can be many instances for each aircraft type. Every aircraft type must have a friendly name for this type, and more details about this type. For example a class named F16 will have a static member FriendlyName with the value of "Lockheed Martin F-16 Fighting Falcon". Other programmers should be able to add more aircrafts, although they must be enforced to create the same static details about the types of the aircrafts. In some GUI, there should be a way to let the user see the list of available types (with the details such as FriendlyName) and add or remove instances of the aircrafts, saved, lets say, to some XML file. So, basically, if I could enforce inherited classes to implement static members and methods, I would enforce the aircraft types to have static members such as FriendlyName. Sadly I cannot do that. So, what would be the best design for this scenario?

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  • Does oneway declaration in Android .aidl guarantee that method will be called in a separate thread?

    - by Dan Menes
    I am designing a framework for a client/server application for Android phones. I am fairly new to both Java and Android (but not new to programming in general, or threaded programming in particular). Sometimes my server and client will be in the same process, and sometimes they will be in different processes, depending on the exact use case. The client and server interfaces look something like the following: IServer.aidl: package com.my.application; interface IServer { /** * Register client callback object */ void registerCallback( in IClient callbackObject ); /** * Do something and report back */ void doSomething( in String what ); . . . } IClient.aidl: package com.my.application; oneway interface IClient { /** * Receive an answer */ void reportBack( in String answer ); . . . } Now here is where it gets interesting. I can foresee use cases where the client calls IServer.doSomething(), which in turn calls IClient.reportBack(), and on the basis of what is reported back, IClient.reportBack() needs to issue another call to IClient.doSomething(). The issue here is that IServer.doSomething() will not, in general, be reentrant. That's OK, as long as IClient.reportBack() is always invoked in a new thread. In that case, I can make sure that the implementation of IServer.doSomething() is always synchronized appropriately so that the call from the new thread blocks until the first call returns. If everything works the way I think it does, then by declaring the IClient interface as oneway, I guarantee this to be the case. At least, I can't think of any way that the call from IServer.doSomething() to IClient.reportBack() can return immediately (what oneway is supposed to ensure), yet IClient.reportBack still be able to reinvoke IServer.doSomething recursively in the same thread. Either a new thread in IServer must be started, or else the old IServer thread can be re-used for the inner call to IServer.doSomething(), but only after the outer call to IServer.doSomething() has returned. So my question is, does everything work the way I think it does? The Android documentation hardly mentions oneway interfaces.

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  • PyQt threads and signals - how to properly retrieve values

    - by Cawas
    Using Python 2.5 and PyQt, I couldn't find any question this specific in Python, so sorry if I'm repeating the other Qt referenced questions below, but I couldn't easily understand that C code. I've got two classes, a GUI and a thread, and I'm trying to get return values from the thread. I've used the link in here as base to write my code, which is working just fine. To sum it up and illustrate the question in code here (I don't think this code will run on itself): class MainWindow (QtGui.QWidget): # this is just a reference and not really relevant to the question def __init__ (self, parent = None): QtGui.QWidget.__init__(self, parent) self.thread = Worker() # this does not begin a thread - look at "Worker.run" for mor details self.connect(self.thread, QtCore.SIGNAL('finished()'), self.unfreezeUi) self.connect(self.thread, QtCore.SIGNAL('terminated()'), self.unfreezeUi) self.connect(self.buttonDaemon, QtCore.SIGNAL('clicked()'), self.pressDaemon) # the problem begins below: I'm not using signals, or queue, or whatever, while I believe I should def pressDaemon (self): self.buttonDaemon.setEnabled(False) if self.thread.isDaemonRunning(): self.thread.setDaemonStopSignal(True) self.buttonDaemon.setText('Daemon - converts every %s sec'% args['daemonInterval']) else: self.buttonConvert.setEnabled(False) self.thread.startDaemon() self.buttonDaemon.setText('Stop Daemon') self.buttonDaemon.setEnabled(True) # this whole class is just another reference class Worker (QtCore.QThread): daemonIsRunning = False daemonStopSignal = False daemonCurrentDelay = 0 def isDaemonRunning (self): return self.daemonIsRunning def setDaemonStopSignal (self, bool): self.daemonStopSignal = bool def __init__ (self, parent = None): QtCore.QThread.__init__(self, parent) self.exiting = False self.thread_to_run = None # which def will be running def __del__ (self): self.exiting = True self.thread_to_run = None self.wait() def run (self): if self.thread_to_run != None: self.thread_to_run(mode='continue') def startDaemon (self, mode = 'run'): if mode == 'run': self.thread_to_run = self.startDaemon # I'd love to be able to just pass this as an argument on start() below return self.start() # this will begin the thread # this is where the thread actually begins self.daemonIsRunning = True self.daemonStopSignal = False sleepStep = 0.1 # don't know how to interrupt while sleeping - so the less sleepStep, the faster StopSignal will work # begins the daemon in an "infinite" loop while self.daemonStopSignal == False and not self.exiting: # here, do any kind of daemon service delay = 0 while self.daemonStopSignal == False and not self.exiting and delay < args['daemonInterval']: time.sleep(sleepStep) # delay is actually set by while, but this holds for N second delay += sleepStep # daemon stopped, reseting everything self.daemonIsRunning = False self.emit(QtCore.SIGNAL('terminated')) Tho it's quite big, I hope this is pretty clear. The main point is on def pressDaemon. Specifically all 3 self.thread calls. The last one, self.thread.startDaemon() is just fine, and exactly as the example. I doubt that represents any issue. The problem is being able to set the Daemon Stop Signal and retrieve the value if it's running. I'm not sure that it's possible to set a stop signal on QtCore.QtThread, because I've tried doing the same way and it didn't work. But I'm pretty sure it's not possible to retrieve a return result from the emit. So, there it is. I'm using direct calls to the thread class, and I'm almost positive that's not a good design and will probably fail when running under stress. I read about that queue, but I'm not sure it's the proper solution here, or if I should be using Qt at all, since this is Python. And just maybe there's nothing wrong with the way I'm doing.

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  • How GC collects resources in a static member in C#?

    - by carter-boater
    Dear all, I have a piece of code like this: Class Program { static StreamReader sr = null; static int var=0; static Program() { sr = new StreamReader("input.txt") } ~Program() { sr.Dispose(); } static void main(string args[]) { //do something with input here } } This may not be a good practice, but I just want to use this example to ask how the deconstructor and GC works. My question is: Will ~Program() get called at a non-determined time or it won't be called at all in this case. If the deconstructor won't get called, then how GC collect the unmanaged resources and managed resources. Thank you very much!

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  • What is the best way to attach static methods to classes rather than to instances of a class?

    - by John Gietzen
    If I have a method for calculating the greatest common divisor of two integers as: public static int GCD(int a, int b) { return b == 0 ? a : GCD(b, a % b); } What would be the best way to attach that to the System.Math class? Here are the three ways I have come up with: public static int GCD(this int a, int b) { return b == 0 ? a : b.GCD(a % b); } // Lame... var gcd = a.GCD(b); and: public static class RationalMath { public static int GCD(int a, int b) { return b == 0 ? a : GCD(b, a % b); } } // Lame... var gcd = RationalMath.GCD(a, b); and: public static int GCD(this Type math, int a, int b) { return b == 0 ? a : typeof(Math).GCD(b, a % b); } // Neat? var gcd = typeof(Math).GCD(a, b); The desired syntax is Math.GCD since that is the standard for all mathematical functions. Any suggestions? What should I do to get the desired syntax?

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  • What is the best way to attach extenstion methods to static classes rather than to instances of a cl

    - by John Gietzen
    If I have a method for calculating the greatest common divisor of two integers as: public static int GCD(int a, int b) { return b == 0 ? a : GCD(b, a % b); } What would be the best way to attach that to the System.Math class? Here are the three ways I have come up with: public static int GCD(this int a, int b) { return b == 0 ? a : b.GCD(a % b); } // Lame... var gcd = a.GCD(b); and: public static class RationalMath { public static int GCD(int a, int b) { return b == 0 ? a : GCD(b, a % b); } } // Lame... var gcd = RationalMath.GCD(a, b); and: public static int GCD(this Type math, int a, int b) { return b == 0 ? a : typeof(Math).GCD(b, a % b); } // Neat? var gcd = typeof(Math).GCD(a, b); The desired syntax is Math.GCD since that is the standard for all mathematical functions. Any suggestions? What should I do to get the desired syntax?

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  • How do I change an existing XCode target from dynamic to static?

    - by Eric
    I'm working with an existing project that produces a dynamic library (Cocoa API). I'd rather generate a static library, but if I change the [Linking|Mach-O Type] field from "Dynamic Library" to "Static Library", both the Clean Project and Build Project complain that the target has an invalid MACH_O_TYPE value of 'staticlib'. Is there a straightforward way to get the build to produce a static .a file? Thanks, Eric

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  • IOC - Should util classes with static helper methods be wired up with IOC?

    - by Greg
    Hi, Just trying to still get my head around IOC principles. Q1: Static Methods - Should util classes with static helper methods be wired up with IOC? For example if I have a HttpUtils class with a number of static methods, should I be trying to pass it to other business logic classes via IOC? Follow on questions for this might be: Q2: Singletons - What about things like logging where you may typically get access to it via a Logger.getInstance() type call. Would you normally leave this as is, and NOT use IOC for injecting the logger into business classes that need it? Q3: Static Classes - I haven't really used this concept, but are there any guidelines for how you'd typically handle this if you were moving to an IOC based approach. Thanks in advance.

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