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• Most watched videos this week

  - by Jan Hancic

  I have a youtube like web-page where users upload&watch videos. I would like to add a "most watched videos this week" list of videos to my page. But this list should not contain just the videos that ware uploaded in the previous week, but all videos. I'm currently recording views in a column, so I have no information on when a video was watched. So now I'm searching for a solution to how to record this data. The first is the most obvious (and the correct one, as far as I know): have a separate table in which you insert a new line every time you want to record a new view (storing the ID of the video and the timestamp). I'm worried that I would quickly get huge amounts of data in this table, and queries using this table would be extremely slow (we get about 3 million views a month). The second solution isn't as flexible but is more easy on the database. I would add 7 columns to the "videos" table (one for each day of the week): views_monday, views_tuesday , views_wednesday, ... And increment the value in the correct column based on the day it is. And I would reset the current day's column to 0 at midnight. I could then easily get the most watched videos of the week by summing this 7 columns. What do you think, should I bother with the first solution or will the second one suffice for my case? If you have a better solution please share! Oh, I'm using MySQL.

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• LINQ to XML query attributes

  - by kb

  Hi using LINQ to XML, this is a sample of my XML <shows> <Show Code="456" Name="My Event Name"> <Event Code="2453" VenueCode="39" Date="2010-04-13 10:30:00" /> <Event Code="2454" VenueCode="39" Date="2010-04-13 13:30:00" /> <Event Code="2455" VenueCode="39" Date="2010-04-14 10:30:00" /> <Event Code="2456" VenueCode="39" Date="2010-04-14 13:30:00" /> <Event Code="2457" VenueCode="39" Date="2010-04-15 10:30:00" /> </Show> <Show... /> <Show... /> </shows> How do I return a list of the Dates for a specfic show? I am passing the show code ("456") in the querystring and want all the dates/times returned as a list. This is the code i have so far: XDocument xDoc = XDocument.Load("path to xml"); var feeds = from feed in xDoc.Descendants("Show") where feed.Attribute("Code").Equals("456") select new { EventDate = feed.Attribute("Date").Value }; foreach(var feed in feeds) { Response.Write(feed.EventDate + "<br />"); } But i get no results returned

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• jQuery indexOf select box manipulation

  - by kenny99

  Hi, I'm trying to figure out how to remove options from a select box when that option has been selected in an adjacent select box. Basically the user has the option to add multiple records here via select boxes, but I want to remove the list of options available to them so that, for example, they can't enter the same value in two select boxes. When an Add More button is clicked, I fade in the next select box container. A number of select boxes have been generated by PHP and I use JS to hide them. Each select box has a unique number appended to the ID, so i want to access those select boxes which contain the string "other_pet_types", then I want to iterate through the currently visible ones and build an array of the values which have been selected, which I will then remove from the list of options in the newly displayed select box. This is what I have so far, but it's definitely not right - I can't get the initial test on the ID to work. Any pointers greatly appreciated as i realise i'm pretty wide of the mark at the moment! var vals = new Array(); //build array with currently selected options $('p.mult_entries select').each(function(){ vals += $(this).val(); }); $("p.mult_entries:hidden:first").fadeIn("slow", function() { $(this).find(('select').attr('id').indexOf('other_pet_types') > 0).each(function(){ console.log($(this).val()); //as expected prints nothing - need to iterate through the options of the above select //once i extract the correct values, iterate through new select box and use inArray to remove options where that value already exists in one of previous select boxes }); });

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• c# Why can't open generic types be passed as parameters?

  - by Rich Oliver

  Why can't open generic types be passed as parameters. I frequently have classes like: public class Example<T> where T: BaseClass { public int a {get; set;} public List<T> mylist {get; set;} } Lets say BaseClass is as follows; public BaseClass { public int num; } I then want a method of say: public int MyArbitarySumMethod(Example example)//This won't compile Example not closed { int sum = 0; foreach(BaseClass i in example.myList)//myList being infered as an IEnumerable sum += i.num; sum = sum * example.a; return sum; } I then have to write an interface just to pass this one class as a parameter as follows: public interface IExample { public int a {get; set;} public IEnumerable<BaseClass> myIEnum {get;} } The generic class then has to be modified to: public class Example<T>: IExample where T: BaseClass { public int a {get; set;} public List<T> mylist {get; set;} public IEnumerable<BaseClass> myIEnum {get {return myList;} } } That's a lot of ceremony for what I would have thought the compiler could infer. Even if something can't be changed I find it psychologically very helpful if I know the reasons / justifications for the absence of Syntax short cuts.

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• How do I convert a simple ruby flashcard program into a ROR app?

  - by Mark Wilbur

  What I'm trying to do is make a basic flashcard app on rails. At this point, all I'm looking for is the functionality to iterate through a list of flashcards, quiz the user and let the user know if they were right or not. In ruby, it didn't take me long to write: class Card attr_accessor :answer, :question def initialize(answer = "", question="") @answer = answer @question = question end def quiz puts "What does #@question mean?" answer = gets.chomp if answer == @answer puts "Right" return true else puts "Wrong" return answer end end end class Cardlist attr_accessor :Cards def initialize(Cards = []) @Cards = Cards end def quiz Cards.each do |w| w.quiz end end end The problem I'm having with rails is figuring out where to put the logic to loop through all the cards in the list. I've made models specifying that Card belongs_to cardlist and that Cardlist has_many cards. I know application logic should go in the controller, but if I were to make a "quiz" action for my Cardlist controller, how would I make it iterate through all the cards? After each "quiz" page generated, I'd need to get an answer back from the user, respond (maybe flash) whether it was right or not and then continue onto the next question. Would any of that logic have to go into the view in order to make sure it's sending back the user inputted answers to the controller?

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• PageableListView Not rendering my data as required

  - by Robin

  i am working on wicket, where i am supposed to show my data's under <tr> <td>Name</td> <td>Single Player Score</td> <td>Double Player Score</td> <td>Total Score</td> </tr> <tr wicket:id="data"> <td wicket:id="name"></td> <td wicket:id="singlePlayerScore"></td> <td wicket:id="doublePlayerScore"></td> <td wicket:id="totalScore"></td> </tr> My Player model class is as: Player class with attributes singlePlayerScore, doublePlayerScore(), name with getter and setter and also a list data obtained from database. Data from SQLQuery is as; name score gamemode A 200 singlePlayerMode A 100 doublePLayerMode B 400 singlePlayerMode B 300 doublePLayerMode dataList == player.getScoreList(); My PageableListView is as: final PageableListView listView = new PageableListView("data",dataList,10){ @Override protected void populateItem(Item item){ player = (Player)item.getModelObject(); item.add(Label("name",player.getName())); item.add(Label("singlePlayerScore",player.getName())); item.add(Label("doublePlayerScore",player.getName())); item.add(Label("totalScore",String.valueOf(player.getSinglePlayerScore()+player.getDoublePlayerScore()))); } } My Problem is as: What view i get is as: Name single Player Score Double Player Score Total Score A 0 100 100 A 200 0 200 B 0 300 300 B 400 0 400 How do i achieve below view on my webpage? Name single Player Score Double Player Score Total Score A 200 100 300 B 400 300 700 Please help me as to why is this happening? I guess my list has size four that's one reason why as to it is rendering the view? So what can i do to get as require rendering view?

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• Fast path cache generation for a connected node graph

  - by Sukasa

  I'm trying to get a faster pathfinding mechanism in place in a game I'm working on for a connected node graph. The nodes are classed into two types, "Networks" and "Routers." In this picture, the blue circles represent routers and the grey rectangles networks. Each network keeps a list of which routers it is connected to, and vice-versa. Routers cannot connect directly to other routers, and networks cannot connect directly to other networks. Networks list which routers they're connected to Routers do the same I need to get an algorithm that will map out a path, measured in the number of networks crossed, for each possible source and destination network excluding paths where the source and destination are the same network. I have one right now, however it is unusably slow, taking about two seconds to map the paths, which becomes incredibly noticeable for all connected players. The current algorithm is a depth-first brute-force search (It was thrown together in about an hour to just get the path caching working) which returns an array of networks in the order they are traversed, which explains why it's so slow. Are there any algorithms that are more efficient? As a side note, while these example graphs have four networks, the in-practice graphs have 55 networks and about 20 routers in use. Paths which are not possible also can occur, and as well at any time the network/router graph topography can change, requiring the path cache to be rebuilt. What approach/algorithm would likely provide the best results for this type of a graph?

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• jQuery preventing RedirectToAction from working?

  - by DaveDev

  I'm trying to redirect the user if they login successfully but the code I have on my page seems to be preventing the redirection from working. If I remove the jQuery below the redirection works. Can somebody tell me tell me if there's something I'm doing wrong? Thanks I have the following Action: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Login(User user) { var myErrors = new Dictionary<string, string>(); try { if (ModelState.IsValid) { if (userRepository.ValidUser(user)) { return RedirectToAction("Index", "Group", new {page = (int?)null}); } else { return Json("Username or password seems to be incorrect"); } } else { foreach (KeyValuePair<string, ModelState> keyValuePair in ViewData.ModelState) { if (keyValuePair.Value.Errors.Count > 0) { List<string> errors = new List<string>(); myErrors.Add(keyValuePair.Key, keyValuePair.Value.Errors[0].ErrorMessage); } } return Json(myErrors); } } catch (Exception) { return Json("Invalid"); } } and the following code on my page: <script language="javascript" type="text/javascript"> $(document).ready(function() { $("#SaveSuccess").hide(); $("#btnLogin").click(function() { $("form").submit(function(event) { var formData = $(this).serialize(); $.post($(this).attr("action"), formData, function(res) { ShowErrors(res); if (res == true) { $("#SaveSuccess").text("Saved"); } else { $("#divError").html(res); } $("#SaveSuccess").fadeIn(100); }, "json"); return false; }); }); }); </script>

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• Designing a chain of states

  - by devoured elysium

  I want to model a kind of FSM(Finite State Machine). I have a sequence of states (let's say, from StateA to StateZ). This sequence is called a Chain and is implemented internally as a List. I will add states by the order I want them to run. My purpose is to be able to make a sequence of actions in my computer (for example, mouse clicks). (I know this has been done a zillion times). So a state is defined as a: boolean Precondition() <- Checks to see if for this state, some condition is true. For example, if I want to click in the Record button of a program, in this method I would check if the program's process is running or not. If it is, go to the next state in the chain list, otherwise, go to what was defined as the fail state (generally is the first state of them all). IState GetNextState() <- Returns the next state to evaluate. If Precondition() was sucessful, it should yield the next state in the chain otherwise it should yield the fail state. Run() Simply checks the Precondition() and sets the internal data so GetNextState() works as expected. So, a naive approach to this would be something like this: Chain chain = new Chain(); //chain.AddState(new State(Precondition, FailState, NextState) <- Method structure chain.AddState(new State(new WinampIsOpenCondition(), null, new <problem here, I want to referr to a state that still wasn't defined!>); The big problem is that I want to make a reference to a State that at this point still wasn't defined. I could circumvent the problem by using strings when refrering to states and using an internal hashtable, but isn't there a clearer alternative? I could just pass only the pre-condition and failure states in the constructor, having the chain just before execution put in each state the correct next state in a public property but that seems kind of awkward.

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• Eclipse BIRT - Unnecessary inline style with external CSS when rendering HTML

  - by Etienne

  Hello! I am designing a report using external CSS with BIRT 2.5. When BIRT renders the html report, it creates copies of each external style to inline styles (name style_x) in the resulting html. The report.design contains: <list-property name="cssStyleSheets"> <structure> <property name="fileName">… mycss.css</property> <property name="externalCssURI"> http://.../mycss.css </property> </structure> </list-property> The resulting html contains: <style type="text/css"> .style_0 {…} .style_1 {…} …. </style> <link rel="stylesheet" type="text/css" href="http://.../mycss.css"></link> For each reference of my styles, the rendered html elements use both styles usually like this: <div class="style_x myclass" …. > …. </div> Is there any way to get rid of the useless inline styles when rendering html?

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• ListView - Index and Position Behavior upon restart()

  - by tunneling

  I am using a ListView with an ArrayAdapter that holds objects. When I select an item, I am capturing the position and index of the selected item. If I scroll down prior to selection, the position and index represent the location of the item in the list. Selecting that items takes me to another activity. When I use the back button to return to the list, it seems that the ListView get's a new position and index for the visible items. As a result, I can't figure out how to reference the selected item during the restart() of the ListView Activity. I have tried to caputure position and index, but as I've said, they change upon returning to the Activity. Is my understanding of the ListView "redraw" correct? Does it renumber my items based on what's visible? -When in the life cycle is getView() called? Is there a way to force an update to the ListView so that my caputured index still points to the same object? Thanks, Jason

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• Scheme: Mysterious void in pattern match.

  - by Schemer

  Hi. I am writing a function called annotate that uses match-lambda -- often with recursive calls to annotate. Here is one of the pattern matches: (`(lambda (,<param1> . ,<params>) ,<stmts>) `(CLOSURE ENV (,<param1> . ,<params>) (lambda (ENV) ,(map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))))) However, when this pattern is matched this is what returns: '(CLOSURE ENV (x) (lambda (ENV) ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y)))))) #<void>) Specifically I can't figure out where "void" is coming from. In fact, if I include the line: ,(displayln (map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))) it prints: ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y))))) notably without "void". If someone could tell me what the problem is it would be greatly appreciated. Thanks.

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• Increment the number of times an article has been read

  - by r.sendecky

  I have a situation where I need to increase the number of time article has been read. Once someone opens an article it should be reflected in the database by incrementing number of reads by one. Simple. Sending POST request to the server increments the number of reads by one. The article in question is supplied via URL parameter. Doing it manually by typing the URL in a browser works as expected. So server side is not at fault. My problems start with the javascript side of it or rather jquery. I hook the event to the article link. So every time a user clicks on the article link it increments the number of reads like so: $('#list-articles .article-link').click(function(e){ var oid = $(this).parent().parent().attr('data-oid').toString(); //Get the article id $.post( "/articles/viewed/" + oid ); }); Now this does not work! Number is not increased. I don't prevent default action since I need the link to actually open and display the article. Now if I put an alert right after the post like this: $('#list-articles .article-link').click(function(e){ var oid = $(this).parent().parent().attr('data-oid').toString(); //Get the article id $.post( "/articles/viewed/" + oid ); alert(oid); }); This variant works. After I dismiss the alert window, the number is incremented. Why is this so?? How can I fix this to actually work without the alert event present?

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• ActionScript shiftKey Not Working In Full Screen Mode?

  - by Chunk1978

  i've drawn an ellipse sprite and added it to the display list of a container, which is added to the display list of the stage. to move the sprites with the keyboard arrows, it appears that my shiftModifier:Number variable is not working when the stage's display state is set to full screen. shiftModifier works as it should when the stage's display state is set to Normal. stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyboardDown); function onKeyboardDown(evt:KeyboardEvent):void { var shiftModifier:Number = 0.25; if (evt.shiftKey) {shiftModifier = 10;} if (evt.keyCode == Keyboard.UP) {ellipse1.y -= shiftModifier;} if (evt.keyCode == Keyboard.DOWN) {ellipse1.y += shiftModifier;} if (evt.keyCode == Keyboard.LEFT) {ellipse1.x -= shiftModifier;} if (evt.keyCode == Keyboard.RIGHT) {ellipse1.x += shiftModifier;} } fsm.addEventListener(MouseEvent.CLICK, toggleFullScreenMode); function toggleFullScreenMode(evt:MouseEvent):void { if (stage.displayState == StageDisplayState.FULL_SCREEN) {stage.displayState = StageDisplayState.NORMAL;} else {stage.displayState = StageDisplayState.FULL_SCREEN;} } full screen is tested in Safari and Firefox.

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• Two "Calendar" entries listed on iPad - can't write to calendar using EventKit

  - by Neal

  My iOS app integrates with the device's calendar. On my iPad when I view the calendar app and tap the Calendars button on the top left to choose which calendars to show I see one entry named "Calendar". In my app when I loop through available calendars per the code below "Calendar" is listed twice. One is CalDAV for the type, the other is Local. I'm unable to create calendar entries in one of them, I believe the "Local" one, not sure why. Why do I see "Calendar" listed twice when I do NOT see it listed twice in the iCal app? public static List<string> Calendars { get { var calendars = new List<string>(); var ekCalendars = EventStore.Calendars; if (ekCalendars != null && ekCalendars.Length > 0) { foreach (EKCalendar cal in ekCalendars) { if (cal.AllowsContentModifications) calendars.Add(cal.Title); } calendars.Sort(); } return calendars; } }

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• Struts2 Hibernate Login with User table and group table

  - by J2ME NewBiew

  My problem is, i have a table User and Table Group (this table use to authorization for user - it mean when user belong to a group like admin, they can login into admincp and other user belong to group member, they just only read and write and can not login into admincp) each user maybe belong to many groups and each group has been contain many users and they have relationship are many to many I use hibernate for persistence storage. and struts 2 to handle business logic. When i want to implement login action from Struts2 how can i get value of group member belong to ? to compare with value i want to know? Example I get user from username and password then get group from user class but i dont know how to get value of group user belong to it mean if user belong to Groupid is 1 and in group table , at column adminpermission is 1, that user can login into admincp, otherwise he can't my code: User.java /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.model; import java.io.Serializable; import java.util.Date; import java.util.HashSet; import java.util.Set; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.JoinTable; import javax.persistence.ManyToMany; import javax.persistence.Table; import javax.persistence.Temporal; /** * * @author Administrator */ @Entity @Table(name="User") public class User implements Serializable{ private static final long serialVersionUID = 2575677114183358003L; private Long userId; private String username; private String password; private String email; private Date DOB; private String address; private String city; private String country; private String avatar; private Set<Group> groups = new HashSet<Group>(0); @Column(name="dob") @Temporal(javax.persistence.TemporalType.DATE) public Date getDOB() { return DOB; } public void setDOB(Date DOB) { this.DOB = DOB; } @Column(name="address") public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Column(name="city") public String getCity() { return city; } public void setCity(String city) { this.city = city; } @Column(name="country") public String getCountry() { return country; } public void setCountry(String country) { this.country = country; } @Column(name="email") public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL) @JoinTable(name="usergroup",joinColumns={@JoinColumn(name="userid")},inverseJoinColumns={@JoinColumn( name="groupid")}) public Set<Group> getGroups() { return groups; } public void setGroups(Set<Group> groups) { this.groups = groups; } @Column(name="password") public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Id @GeneratedValue @Column(name="iduser") public Long getUserId() { return userId; } public void setUserId(Long userId) { this.userId = userId; } @Column(name="username") public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } @Column(name="avatar") public String getAvatar() { return avatar; } public void setAvatar(String avatar) { this.avatar = avatar; } } Group.java /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.model; import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.Table; /** * * @author Administrator */ @Entity @Table(name="Group") public class Group implements Serializable{ private static final long serialVersionUID = -2722005617166945195L; private Long idgroup; private String groupname; private String adminpermission; private String editpermission; private String modpermission; @Column(name="adminpermission") public String getAdminpermission() { return adminpermission; } public void setAdminpermission(String adminpermission) { this.adminpermission = adminpermission; } @Column(name="editpermission") public String getEditpermission() { return editpermission; } public void setEditpermission(String editpermission) { this.editpermission = editpermission; } @Column(name="groupname") public String getGroupname() { return groupname; } public void setGroupname(String groupname) { this.groupname = groupname; } @Id @GeneratedValue @Column (name="idgroup") public Long getIdgroup() { return idgroup; } public void setIdgroup(Long idgroup) { this.idgroup = idgroup; } @Column(name="modpermission") public String getModpermission() { return modpermission; } public void setModpermission(String modpermission) { this.modpermission = modpermission; } } UserDAO /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.dao; import java.util.List; import org.dejavu.software.model.User; import org.dejavu.software.util.HibernateUtil; import org.hibernate.Query; import org.hibernate.Session; /** * * @author Administrator */ public class UserDAO extends HibernateUtil{ public User addUser(User user){ Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); session.save(user); session.getTransaction().commit(); return user; } public List<User> getAllUser(){ Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); List<User> user = null; try { user = session.createQuery("from User").list(); } catch (Exception e) { e.printStackTrace(); session.getTransaction().rollback(); } session.getTransaction().commit(); return user; } public User checkUsernamePassword(String username, String password){ Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); User user = null; try { Query query = session.createQuery("from User where username = :name and password = :password"); query.setString("username", username); query.setString("password", password); user = (User) query.uniqueResult(); } catch (Exception e) { e.printStackTrace(); session.getTransaction().rollback(); } session.getTransaction().commit(); return user; } } AdminLoginAction /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.view; import com.opensymphony.xwork2.ActionSupport; import org.dejavu.software.dao.UserDAO; import org.dejavu.software.model.User; /** * * @author Administrator */ public class AdminLoginAction extends ActionSupport{ private User user; private String username,password; private String role; private UserDAO userDAO; public AdminLoginAction(){ userDAO = new UserDAO(); } @Override public String execute(){ return SUCCESS; } @Override public void validate(){ if(getUsername().length() == 0){ addFieldError("username", "Username is required"); }if(getPassword().length()==0){ addFieldError("password", getText("Password is required")); } } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getRole() { return role; } public void setRole(String role) { this.role = role; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } } other question. i saw some example about Login, i saw some developers use interceptor, im cant understand why they use it, and what benefit "Interceptor" will be taken for us? Thank You Very Much!

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• Block Cascade Json Serealize?

  - by CrazyJoe

  I have this Class: public class User { public string id{ get; set; } public string name{ get; set; } public string password { get; set; } public string email { get; set; } public bool is_broker { get; set; } public string branch_id { get; set; } public string created_at{get; set;} public string updated_at{get; set;} public UserGroup UserGroup {get;set;} public UserAddress UserAddress { get; set; } public List<UserContact> UserContact {get; set;} public User() { UserGroup = new UserGroup(); UserAddress = new UserAddress(); UserContact = new List<UserContact>(); } } I like to Serealize Only properties , how i block serealization of UserGroup, UserAdress, asn UserContact??? This is my Serealization function: public static string Serealize<T>(T obj) { System.Runtime.Serialization.Json.DataContractJsonSerializer serializer = new System.Runtime.Serialization.Json.DataContractJsonSerializer(obj.GetType()); MemoryStream ms = new MemoryStream(); serializer.WriteObject(ms, obj); return Encoding.UTF8.GetString(ms.ToArray(), 0,(int)ms.Length); }

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• How should I deal with floating numbers that numbers that can get so small that the become zero

  - by Tristan Havelick

  So I just fixed an interesting bug in the following code, but I'm not sure the approach I took it the best: p = 1 probabilities = [ ... ] # a (possibly) long list of numbers between 0 and 1 for wp in probabilities: if (wp > 0): p *= wp # Take the natural log, this crashes when 'probabilites' is long enough that p ends up # being zero try: result = math.log(p) Because the result doesn't need to be exact, I solved this by simply keeping the smallest non-zero value, and using that if p ever becomes 0. p = 1 probabilities = [ ... ] # a long list of numbers between 0 and 1 for wp in probabilities: if (wp > 0): old_p = p p *= wp if p == 0: # we've gotten so small, its just 0, so go back to the smallest # non-zero we had p = old_p break # Take the natural log, this crashes when 'probabilites' is long enough that p ends up # being zero try: result = math.log(p) This works, but it seems a bit kludgy to me. I don't do a ton of this kind of numerical programming, and I'm not sure if this is the kind of fix people use, or if there is something better I can go for.

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• How to detect whether an EventWaitHandle is waiting?

  - by AngryHacker

  I have a fairly well multi-threaded winforms app that employs the EventWaitHandle in a number of places to synchronize access. So I have code similar to this: List<int> _revTypes; EventWaitHandle _ewh = new EventWaitHandle(false, EventResetMode.ManualReset); void StartBackgroundTask() { _ewh.Reset(); Thread t = new Thread(new ThreadStart(LoadStuff)); t.Start(); } void LoadStuff() { _revTypes = WebServiceCall.GetRevTypes() // ...bunch of other calls fetching data from all over the place // using the same pattern _ewh.Set(); } List<int> RevTypes { get { _ewh.WaitOne(); return _revTypes; } } Then I just call .RevTypes somewehre from the UI and it will return data to me when LoadStuff has finished executing. All this works perfectly correctly, however RevTypes is just one property - there are actually several dozens of these. And one or several of these properties are holding up the UI from loading in a fast manner. Short of placing benchmark code into each property, is there a way to see which property is holding the UI from loading? Is there a way to see whether the EventWaitHandle is forced to actually wait?

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• How can I find the common ancestor of two nodes in a binary tree?

  - by Siddhant

  The Binary Tree here is not a Binary Search Tree. Its just a Binary Tree. The structure could be taken as - struct node { int data; struct node *left; struct node *right; }; The maximum solution I could work out with a friend was something of this sort - Consider this binary tree (from http://lcm.csa.iisc.ernet.in/dsa/node87.html) : The inorder traversal yields - 8, 4, 9, 2, 5, 1, 6, 3, 7 And the postorder traversal yields - 8, 9, 4, 5, 2, 6, 7, 3, 1 So for instance, if we want to find the common ancestor of nodes 8 and 5, then we make a list of all the nodes which are between 8 and 5 in the inorder tree traversal, which in this case happens to be [4, 9, 2]. Then we check which node in this list appears last in the postorder traversal, which is 2. Hence the common ancestor for 8 and 5 is 2. The complexity for this algorithm, I believe is O(n) (O(n) for inorder/postorder traversals, the rest of the steps again being O(n) since they are nothing more than simple iterations in arrays). But there is a strong chance that this is wrong. :-) But this is a very crude approach, and I'm not sure if it breaks down for some case. Is there any other (possibly more optimal) solution to this problem?

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• Java reflection appropriateness

  - by jsn

  This may be a fairly subjective question, but maybe not. My application contains a bunch of forms that are displayed to the user at different times. Each form is a class of its own. Typically the user clicks a button, which launches a new form. I have a convenience function that builds these buttons, you call it like this: buildButton( "button text", new SelectionAdapter() { @Override public void widgetSelected( SelectionEvent e ) { showForm( new TasksForm( args... ) ); } } ); I do this dozens of times, and it's really cumbersome having to make a SelectionAdapter every time. Really all I need for the button to know is what class to instantiate when it's clicked and what arguments to give the constructor, so I built a function that I call like this instead: buildButton( "button text", TasksForm.class, args... ); Where args is an arbitrary list of objects that you could use to instantiate TasksForm normally. It uses reflection to get a constructor from the class, match the argument list, and build an instance when it needs to. Most of the time I don't have to pass any arguments to the constructor at all. The downside is obviously that if I'm passing a bad set of arguments, it can't detect that at compilation time, so if it fails, a dialog is displayed at runtime. But it won't normally fail, and it'll be easy to debug if it does. I think this is much cleaner because I come from languages where the use of function and class literals is pretty common. But if you're a normal Java programmer, would seeing this freak you out, or would you appreciate not having to scan a zillion SelectionAdapters?

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• How to test a Grails Service that utilizes a criteria query (with spock)?

  - by user569825

  I am trying to test a simple service method. That method mainly just returns the results of a criteria query for which I want to test if it returns the one result or not (depending on what is queried for). The problem is, that I am unaware of how to right the corresponding test correctly. I am trying to accomplish it via spock, but doing the same with any other way of testing also fails. Can one tell me how to amend the test in order to make it work for the task at hand? (BTW I'd like to keep it a unit test, if possible.) The EventService Method public HashSet<Event> listEventsForDate(Date date, int offset, int max) { date.clearTime() def c = Event.createCriteria() def results = c { and { le("startDate", date+1) // starts tonight at midnight or prior? ge("endDate", date) // ends today or later? } maxResults(max) order("startDate", "desc") } return results } The Spock Specification package myapp import grails.plugin.spock.* import spock.lang.* class EventServiceSpec extends Specification { def event def eventService = new EventService() def setup() { event = new Event() event.publisher = Mock(User) event.title = 'et' event.urlTitle = 'ut' event.details = 'details' event.location = 'location' event.startDate = new Date(2010,11,20, 9, 0) event.endDate = new Date(2011, 3, 7,18, 0) } def "list the Events of a specific date"() { given: "An event ranging over multiple days" when: "I look up a date for its respective events" def results = eventService.listEventsForDate(searchDate, 0, 100) then: "The event is found or not - depending on the requested date" numberOfResults == results.size() where: searchDate | numberOfResults new Date(2010,10,19) | 0 // one day before startDate new Date(2010,10,20) | 1 // at startDate new Date(2010,10,21) | 1 // one day after startDate new Date(2011, 1, 1) | 1 // someday during the event range new Date(2011, 3, 6) | 1 // one day before endDate new Date(2011, 3, 7) | 1 // at endDate new Date(2011, 3, 8) | 0 // one day after endDate } } The Error groovy.lang.MissingMethodException: No signature of method: static myapp.Event.createCriteria() is applicable for argument types: () values: [] at myapp.EventService.listEventsForDate(EventService.groovy:47) at myapp.EventServiceSpec.list the Events of a specific date(EventServiceSpec.groovy:29)

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• Searching For A Record After A LINQ query

  - by Justin

  I'm confused to why this is happening. I'm new to LINQ so I'm clearly missing something here, that is probably pretty easy. I've looked up help on the topic, but I don't really know what to ask so I haven't found any answers that really address my question. This doesn't work It throws an EntityCommandExecutionException when the FirstOrDefault method is executed. var query = from band in context.BandsEntitySet where band.ID == 12345 select band; string venueName = "Willis Park"; foreach (var item in query) { var venue = context.VenueEntitySet.FirstOrDefault(r => r.Venue.Equals(venueName)); } This works var query = from band in context.BandsEntitySet where band.ID == 12345 select band; var bandList = query.toList(); string venueName = "Willis Park"; foreach (var item in bandList) { var venue = context.VenueEntitySet.FirstOrDefault(r => r.Venue.Equals(venueName)); } My question is simple: Why is the exception being thrown? And why does creating a list from the query allow me to use the FirstOrDefault method? Exception Message: A first chance exception of type 'System.Data.EntityCommandExecutionException' occurred in System.Data.Entity.dll I guess I am wrong in my assumption that query is a list? Then what is it exactly? I'm confused because this doesn't throw an exception: foreach (var item in query) { var area = item.VenueArea; } I'd appreciate any help on this issue. thanks, Justin

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• Loading views dynamically

  - by Dan

  Case 1: I have created View-based sample application and tried execute below code. When I press on "Job List" button it should load another view having "Back Btn" on it. In test function, if I use [self.navigationController pushViewController:jbc animated:YES]; nothing gets loaded, but if I use [self presentModalViewController:jbc animated:YES]; it loads another view haveing "Back Btn" on it. Case 2: I did create another Navigation Based Applicaton and used [self.navigationController pushViewController:jbc animated:YES]; it worked as I wanted. Can someone please explain why it was not working in Case 1. Does it has something to do with type of project that is selected? @interface MWViewController : UIViewController { } -(void) test; @end @interface JobViewCtrl : UIViewController { } @end @implementation MWViewController (void)viewDidLoad { UIButton* btn = [UIButton buttonWithType:UIButtonTypeRoundedRect]; btn.frame = CGRectMake(80, 170, 150, 35); [btn setTitle:@"Job List!" forState:UIControlStateNormal]; [btn addTarget:self action:@selector(test) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:btn]; [super viewDidLoad]; } -(void) test { JobViewCtrl* jbc = [[JobViewCtrl alloc] init]; [self.navigationController pushViewController:jbc animated:YES]; //[self presentModalViewController:jbc animated:YES]; [jbc release]; } (void)dealloc { [super dealloc]; } @end @implementation JobViewCtrl -(void) loadView { self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; self.view.backgroundColor = [UIColor grayColor]; UIButton* btn = [UIButton buttonWithType:UIButtonTypeRoundedRect]; btn.frame = CGRectMake(80, 170, 150, 35); [btn setTitle:@"Back Btn!" forState:UIControlStateNormal]; [self.view addSubview:btn]; } @end

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• algorithm to find longest non-overlapping sequences

  - by msalvadores

  I am trying to find the best way to solve the following problem. By best way I mean less complex. As an input a list of tuples (start,length) such: [(0,5),(0,1),(1,9),(5,5),(5,7),(10,1)] Each element represets a sequence by its start and length, for example (5,7) is equivalent to the sequence (5,6,7,8,9,10,11) - a list of 7 elements starting with 5. One can assume that the tuples are sorted by the start element. The output should return a non-overlapping combination of tuples that represent the longest continuos sequences(s). This means that, a solution is a subset of ranges with no overlaps and no gaps and is the longest possible - there could be more than one though. For example for the given input the solution is: [(0,5),(5,7)] equivalent to (0,1,2,3,4,5,6,7,8,9,10,11) is it backtracking the best approach to solve this problem ? I'm interested in any different approaches that people could suggest. Also if anyone knows a formal reference of this problem or another one that is similar I'd like to get references. BTW - this is not homework. Edit Just to avoid some mistakes this is another example of expected behaviour for an input like [(0,1),(1,7),(3,20),(8,5)] the right answer is [(3,20)] equivalent to (3,4,5,..,22) with length 20. Some of the answers received would give [(0,1),(1,7),(8,5)] equivalent to (0,1,2,...,11,12) as right answer. But this last answer is not correct because is shorter than [(3,20)].

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