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• SPRING: How do you programmatically instantiate classes based on information passed from Flex UI

  - by babyangel86

  Imagine the UI passes back an XMl node as such: <properties> <type> Source </type> <name> Blooper </name> <delay> <type> Deterministic </type> <parameters> <param> 4 </param> </parameters> <delay> <batch> <type> Erlang </type> <parameters> <param> 4 </param> <param> 6 </param> </parameters> <batch> And behind the scene what it is asking that you instantiate a class as such: new Source("blooper", new Exp(4), new Erlang(4,6); The problem lies in the fact that you don't know what class you will need to processing, and you will be sent a list of these class definitions with instructions on how they can be linked to each other. I've heard that using a BeanFactoryPostProcessor might be helpful, or a property editor/convertor. However I am at a loss as to how best to use them to solve my problem. Any help you can provide will be much appreciated.

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• gluLookAt vectors and FPS-style camera

  - by Kevin Pamplona

  I am attempting to implemented an FPS-style camera by updating three vectors: EYE, DIR, UP. These vectors are the same that are used by gluLookAt (since gluLookAt is specified by the position of the camera, the direction it is looking at, and an up vector). I have already implemented the left-right and up-down strafing movements, but I'm having a lot of trouble understanding the math behind making the camera look-around while remaining stationary. In this case, the EYE vector remains the same, while I must update DIR and UP. Below is the code I tried, but it doesn't seem to work properly. Any suggestions? Thanks. void Transform::left(float degrees, vec3& dir, vec3& up) { vec3 axis; axis = glm::normalize(up); mat3 R = rotate(-degrees, axis); dir = R*dir; dir = R*up; }; void Transform::up(float degrees, vec3& dir, vec3& up) { vec3 axis; axis=glm::normalize(glm::cross(dir,up)); mat3 R = rotate(-degrees, axis); dir = R*dir-; up = R*up; };

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• VB.NET trying simple captcha

  - by Pride Grimm

  I'm trying to write a simple captcha program in vb.net. I'm just wanting to make an image from random numbers and display it, check the answer, and then proceed. I'm pretty new to vb.net, so I found some code to generate the information. I will cite the owner when I find it again (http://www.knowlegezone.com/80/article/Technology/Software/Asp-Net/Simple-ASP-NET-CAPTCHA-Tutorial) This is in the onload() of default2.aspx Public Sub returnNumer() Dim num1 As New Random Dim num2 As New Random Dim numQ1 As Integer Dim numQ2 As Integer Dim QString As String numQ1 = num1.Next(10, 15) numQ2 = num2.Next(17, 31) QString = numQ1.ToString + " + " + numQ2.ToString + " = " Session("answer") = numQ1 + numQ2 Dim bitmap As New Bitmap(85, 35) Dim Grfx As Graphics = Graphics.FromImage(bitmap) Dim font As New Font("Arial", 18, FontStyle.Bold, GraphicsUnit.Pixel) Dim Rect As New Rectangle(0, 0, 100, 50) Grfx.FillRectangle(Brushes.Brown, Rect) Grfx.DrawRectangle(Pens.PeachPuff, Rect) ' Border Grfx.DrawString(QString, font, Brushes.Azure, 0, 0) Response.ContentType = "Image/jpeg" bitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg) bitmap.Dispose() Grfx.Dispose() End Sub So I put this in a separate page, like this This all works find and dandy, but when I get the answer from the session like this Dim literal As String = Convert.ToString(Session("answer")) It's always one behind. So if The images adds to 32, the answer in session isn't 32. But after a refresh (and a new image) the session("answer") will be 32. Is there a way to refresh the session on page 1, after the default2.aspx loads? Is there a better way to do this? I though about trying to run the code all on one page, and trying to set the src of and image to returnNumber(), but I need a bit of help on that one.

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• PHP Resize image down and crop using imagemagick

  - by mr12086

  I'm trying to downsize image uploaded by users at the time of upload. This is no problem but I want to get specific with sizes now. I'm looking for some advice on an algorithm im struggling to produce that will take any shape image - square or rectangle of any widths/heights and downsize it. This image needs to be downsized to a target box size (this changes but is stored in a variable).. So it needs to downsize the image so that both the width and height are larger than the width and height of the target maintaining aspect ratio. but only just.. The target size will be used to crop the image so there is no white space around the edges etc. I'm looking for just the algorithm behind creating the correct resize based on different dimension images - I can handle the cropping, even resizing in most cases but it fails in a few so i'm reaching out. I'm not really asking for PHP code more pseudo. Either is fine obviously. Thanks Kindly.

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• How is a referencing environment generally implemented for closures?

  - by Alexandr Kurilin

  Let's say I have a statically/lexically scoped language with deep binding and I create a closure. The closure will consist of the statements I want executed plus the so called referencing environment, or, to quote this post, the collection of variables which can be used. What does this referencing environment actually look like implementation-wise? I was recently reading about ObjectiveC's implementation of blocks, and the author suggests that behind the scenes you get a copy of all of the variables on the stack and also of all the references to heap objects. The explanation claims that you get a "snapshot" of the referencing environment at the point in time of the closure's creation. Is that more or less what happens, or did I misread that? Is anything done to "freeze" a separate copy of the heap objects, or is it safe to assume that if they get modified between closure creation and the closure executing, the closure will no longer be operating on the original version of the object? If indeed there's copying being made, are there memory usage considerations in situations where one might want to create plenty of closures and store them somewhere? I think that misunderstanding of some of these concepts might lead to tricky issues like the ones Eric Lippert mentions in this blog post. It's interesting because you'd think that it wouldn't make sense to keep a reference to a value type that might be gone by the time the closure is called, but I'm guessing that in C# the compiler will figure out that the variable is needed later and put it into the heap instead. It seems that in most memory-managed languages everything is a reference and thus ObjectiveC is a somewhat unique situation with having to deal with copying what's on the stack.

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• Start dependent application with eunit

  - by ruslander

  I start lager as a dependent application when I run a unit test but for some reason the code under test does not see it. -module(main_tests). -include_lib("eunit/include/eunit.hrl"). main_test_() -> {foreach, fun distr_setup/0, fun distr_cleanup/1, [ fun must_retain/1 ]}. must_retain(_) -> {"Should do ping pong when is fully initialized", fun() -> ?assertEqual(pong, abuse_counter:ping()) end}. %%------------------------------------------------------------------ distr_setup() -> abuse_counter:start_link(), ok. distr_cleanup(_) -> abuse_counter:stop(), ok. Here is the output of the log which is complaining that lager is not defined {undef,[{lager,info,["up and running"],[]} though in the run output is definitely there. Here is how I run it: erl -pa ebin/ ../../deps/*/ebin -s lager -eval 'eunit:test(main_tests,[verbose]), init:stop().' Fails with the output Eshell V5.10.2 (abort with ^G) 1> 17:13:31.506 [info] Application lager started on node nonode@nohost ======================== EUnit ======================== module 'main_tests' undefined 17:13:31.528 [error] CRASH REPORT Process <0.57.0> with 1 neighbours exited with reason: call to undefined function lager:info("up and running") in gen_server:init_it/6 line 328 *unexpected termination of test process* ::**{undef,[{lager,info,["up and running"],[]}**, {abuse_counter,init,1,[{file,"src/abuse_counter.erl"},{line,37}]}, {gen_server,init_it,6,[{file,"gen_server.erl"},{line,304}]}, {proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,239}]}]} ======================================================= Failed: 0. Skipped: 0. Passed: 0. One or more tests were cancelled. Already spent 3-4h hours on google and stack overflow but nothing seems to work. One option is to hide this call behind a ?INFO(Mgs) macro but do not like the idea. Any help will be highly appreciated.

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• Using mod-rewrite to conditionally select existing file in a subdirectory based on Host header?

  - by Kevin Hakanson

  I'm working through a problem where I want to select a different static content file based on the incoming Host header. The simple example is a mapping from URLs to files like this: www.example.com/images/logo.gif - \images\logo.gif skin2.example.com/images/logo.gif - \images\skin2\logo.gif skin3.example.com/images/logo.gif - \images\skin3logo.gif I have this working with the following RewriteRules, but I don't like how I have to repeat myself so much. Each host has the same set of rules, and each RewriteCond and RewriteRule has the same path. I'd like to use the RewriteMap, but I don't know how to use it to map the %{HTTP_HOST} to the path. <VirtualHost *:80> DocumentRoot "C:/Program Files/Apache Software Foundation/Apache2.2/htdocs" ServerName www.example.com ServerAlias skin2.example.com ServerAlias skin3.example.com RewriteEngine On RewriteCond %{HTTP_HOST} skin2.example.com RewriteCond %{DOCUMENT_ROOT}$1/skin2/$2 -f RewriteRule ^(.*)/(.*) $1/skin2/$2 [L] RewriteCond %{HTTP_HOST} skin3.example.com RewriteCond %{DOCUMENT_ROOT}$1/skin3/$2 -f RewriteRule ^(.*)/(.*) $1/skin3/$2 [L] </VirtualHost> The concept behind the rules is if the same filename exists in a subdirectory for that host, use it instead of the direct targeted file. This uses host based subdirectories at the lowest level, and not a top level subdirectory to separate content.

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• Encapsulating user input of data for a class (C++)

  - by Dr. Monkey

  For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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• create board for game with events support in WPF

  - by netmajor

  How can I create board for simple game, looks like for chess,but user could dynamically change number of column and rows? In cells I could insert symbol of pawn, like small image or just ellipse or rectangle with fill. This board should have possibility add and remove pawn from cells and move pown from one cell to another. My first idea was Grid. I do it in code behind, but it's hurt to implement events or everything in runtime create board :/ int size = 12; Grid board = new Grid(); board.ShowGridLines = true; for (int i = 0; i < size;i++ ) { board.ColumnDefinitions.Add(new ColumnDefinition()); board.RowDefinitions.Add(new RowDefinition()); } //komputer Rectangle ai = new Rectangle(); ai.Height = 20; ai.Width = 20; ai.AllowDrop = true; ai.Fill = Brushes.Orange; Grid.SetRow(ai, 0); Grid.SetColumn(ai,0); //czlowiek Rectangle hum = new Rectangle(); hum.Height = 20; hum.Width = 20; hum.AllowDrop = true; hum.Fill = Brushes.Green; Grid.SetRow(hum,size); Grid.SetColumn(hum,size); board.Children.Add(ai); board.Children.Add(hum); this.Content = board; It's a way to do this dynamically col and row change in XAML ? It's better way to implement that board create and implement events on move pawn from one cell to another ?

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• Intermittent bug - IE6 showing file as text in browser, rather than as file download

  - by Richard Ev

  In an ASP.NET WebForms 2.0 site we are encountering an intermittent bug in IE6 whereby a file download attempt results in the contents of the being shown directly in the browser as text, rather than the file save dialog being displayed. Our application allows the user to download both PDF and CSV files. The code we're using is: HttpResponse response = HttpContext.Current.Response; response.Clear(); response.AddHeader("Content-Disposition", "attachment;filename=\"theFilename.pdf\""); response.ContentType = "application/pdf"; response.BinaryWrite(MethodThatReturnsFileContents()); response.End(); This is called from the code-behind click event handler of a button server control. Where are we going wrong with this approach? Edit Following James' answer to this posting, the code I'm using now looks like this: HttpResponse response = HttpContext.Current.Response; response.ClearHeaders(); // Setting cache to NoCache was recommended, but doing so results in a security // warning in IE6 //response.Cache.SetCacheability(HttpCacheability.NoCache); response.AppendHeader("Content-Disposition", "attachment; filename=\"theFilename.pdf\""); response.ContentType = "application/pdf"; response.BinaryWrite(MethodThatReturnsFileContents()); response.Flush(); response.End(); However, I don't believe that any of the changes made will fix the issue.

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• How can I get a custom made set of checkboxes return values in the postback?

  - by AngryHacker

  I have the following in an aspx page: <td colspan="2"> <% DisplayParties(); %> </td> In the code behind for the aspx page, i have this (e.g. I build HTML for the checkboxes): public void DisplayParties() { var s = new StringBuilder(); s.Append("<input type=\"checkbox\" id=\"attorney\" value=\"12345\"/>"); s.Append("<input type=\"checkbox\" id=\"attorney\" value=\"67890\"/>"); s.Append("<input type=\"checkbox\" id=\"adjuster\" value=\"125\"/>"); Response.WriteLine(s.ToString()); } Not my proudest moment, but whatever. The problem is that when this page posts back via some event on the page, I never get these tags in the Request.Form collection. Is this simply how ASP.NET works (e.g. only server-side control post back) or am I missing something simple. My understanding was that a postback should bring back all the form variables.

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• Connecting to an RMI object without registry

  - by Mark Probst

  I think I need to connect to a remote RMI object without going through the registry, but I don't know how. My situation is this: I'm implementing a simple job distribution service which consists of one distributor and multiple workers. The distributor has a registered RMI object to which clients connect to send jobs, and workers connect to accept jobs. Unfortunately the distributor and worker hosts are behind a firewall. To get to the distributor host I am tunneling two ports (one for the registry, one for the distributor object) via SSH, so I can get to the registry and the distributor from outside the firewall. To make that work I have to set "-Djava.rmi.server.hostname=localhost" on the distributor JVM so that the clients connect to their local, tunneled port, instead of the port on the actual distributor host, which is blocked. This creates a problem for the workers, though, because they need to connect to the distributor directly, but because of the "localhost" redirection they behave like clients and try to connect to a port on their own host, which is not available, because I'm not tunneling on the workers (it is impractical). Now, if I could connect to a remote object directly by giving the hostname and port, I could do away both with the registry on the distributor and the "localhost" hack, and make the workers connect properly. How do I do that? Or is there a different solution to this problem?

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• Binding ComboBoxes to enums... in Silverlight!

  - by Domenic

  So, the web, and StackOverflow, have plenty of nice answers for how to bind a combobox to an enum property in WPF. But Silverlight is missing all of the features that make this possible :(. For example: You can't use a generic EnumDisplayer-style IValueConverter that accepts a type parameter, since Silverlight doesn't support x:Type. You can't use ObjectDataProvider, like in this approach, since it doesn't exist in Silverlight. You can't use a custom markup extension like in the comments on the link from #2, since markup extensions don't exist in Silverlight. You can't do a version of #1 using generics instead of Type properties of the object, since generics aren't supported in XAML (and the hacks to make them work all depend on markup extensions, not supported in Silverlight). Massive fail! As I see it, the only way to make this work is to either Cheat and bind to a string property in my ViewModel, whose setter/getter does the conversion, loading values into the ComboBox using code-behind in the View. Make a custom IValueConverter for every enum I want to bind to. Are there any alternatives that are more generic, i.e. don't involve writing the same code over and over for every enum I want? I suppose I could do solution #2 using a generic class accepting the enum as a type parameter, and then create new classes for every enum I want that are simply class MyEnumConverter : GenericEnumConverter<MyEnum> {} What are your thoughts, guys?

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• How do I cast a void pointer to a struct in C?

  - by Rowhawn

  In a project I'm writing code for, I have a void pointer, "implementation", which is a member of a "Hash_map" struct, and points to an "Array_hash_map" struct. The concepts behind this project are not very realistic, but bear with me. The specifications of the project ask that I cast the void pointer "implementation" to an "Array_hash_map" before I can use it in any functions. My question, specifically is, what do I do in the functions to cast the void pointers to the desired struct? Is there one statement at the top of each function that casts them or do I make the cast every time I use "implementation"? Here are the typedefs the structs of a Hash_map and Array_hash_map as well as a couple functions making use of them. typedef struct { Key_compare_fn key_compare_fn; Key_delete_fn key_delete_fn; Data_compare_fn data_compare_fn; Data_delete_fn data_delete_fn; void *implementation; } Hash_map; typedef struct Array_hash_map{ struct Unit *array; int size; int capacity; } Array_hash_map; typedef struct Unit{ Key key; Data data; } Unit; functions: /* Sets the value parameter to the value associated with the key parameter in the Hash_map. */ int get(Hash_map *map, Key key, Data *value){ int i; if (map == NULL || value == NULL) return 0; for (i = 0; i < map->implementation->size; i++){ if (map->key_compare_fn(map->implementation->array[i].key, key) == 0){ *value = map->implementation->array[i].data; return 1; } } return 0; } /* Returns the number of values that can be stored in the Hash_map, since it is represented by an array. */ int current_capacity(Hash_map map){ return map.implementation->capacity; }

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• How to remove the upper right close button

  - by tahdhaze09

  I need to kill the close 'x' button at the top of a jQuery UI modal dialog box. I have a modal that opens with an OK button that redirects to the site. The site behind the modal is in an iframe. When the user agrees to the statement in the dialog box and clicks the 'OK' button, it redirects to the site that is outside the iframe. If the user clicks on the 'x', it goes to the iframe site, which I do not want to have happen. I need the modal to work as a one-way to the site it goes to. It basically forces the user to accept the user agreement. I would post code, but its an intranet site. Thanks everyone for your help! EDIT: This site is a government intranet portal, not a commercial site. So the goal is NOT to trap a user into the site, but rather to let the user know that the use of this site is restricted and to make sure you understand and accept the user agreement or you cannot use the site.

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• In Visual Studio (2008) is there a way to have a custom dependent file on another custom file?

  - by rball

  Instead of a *.cs code behind or beside I'd like to have a *.js file. I'm developing a MVC application an have no need for a code beside because I have controllers, but in certain cases it'd be nice to have a JavaScript code beside or some way to associate the file to the page it's being used on. I suppose I could just name them similarly, but I'm wanting to show the association if possible so there's no question about what the file is for. Typically what I'm talking about is within Visual Studio now under your Global.asax file you will have a plus sign to the left: + Global.asax Once you expand it you'll get - Global.asax Global.asax.cs I'd like the same thing to happen: + Home.spark - Home.spark Home.spark.js Updated: My existing csproj file has a path to the actual file, not sure if that's screwing it up. I've currently got: <ItemGroup> <Content Include="Views\User\Profile.spark.js"> <DependentUpon>Views\User\Profile.spark</DependentUpon> </Content> </ItemGroup> <ItemGroup> <Content Include="Views\User\Profile.spark" /> </ItemGroup> and it's simply just showing the files besides each other.

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• How should I secure my webapp written using Wicket, Spring, and JPA?

  - by Martin

  So, I have an web-based application that is using the Wicket 1.4 framework, and it uses Spring beans, the Java Persistence API (JPA), and the OpenSessionInView pattern. I'm hoping to find a security model that is declarative, but doesn't require gobs of XML configuration -- I'd prefer annotations. Here are the options so far: Spring Security (guide) - looks complete, but every guide I find that combines it with Wicket still calls it Acegi Security, which makes me think it must be old. Wicket-Auth-Roles (guide 1 and guide 2) - Most guides recommend mixing this with Spring Security, and I love the declarative style of @Authorize("ROLE1","ROLE2",etc). I'm concerned about having to extend AuthenticatedWebApplication, since I'm already extending org.apache.wicket.protocol.http.WebApplication, and Spring is already proxying that behind org.apache.wicket.spring.SpringWebApplicationFactory. SWARM / WASP (guide) - This looks the newest (though the main contributor passed away years ago), but I hate all of the JAAS-styled text files that declare permissions for principals. I also don't like the idea of making an Action class for every single thing a user might want to do. Secure models also aren't immediately obvious to me. Plus, there isn't an Authn example. Additionally, it looks like lots of folks recommend mixing the first and second options. I can't tell what the best practice is at all, though.

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• Visual Studio project remains "stuck" when stopped

  - by Traveling Tech Guy

  Hi, Currently developing a connector DLL to HP's Quality Center. I'm using their (insert expelative) COM API to connect to the server. An Interop wrapper gets created automatically by VStudio. My solution has 2 projects: the DLL and a tester application - essentially a form with buttons that call functions in the DLL. Everything works well - I can create defects, update them and delete them. When I close the main form, the application stops nicely. But when I call a function that returns a list of all available projects (to fill a combo box), if I close the main form, VStudio still shows the solution as running and I have to stop it. I've managed to pinpoint a single function in my code that when I call, the solution remains "hung" and if I don't, it closes well. It's a call to a property in the TDC object get_VisibleProjects that returns a List (not the .Net one, but a type in the COM library) - I just iterate over it and return a proper list (that I later use to fill the combo box): public List<string> GetAvailableProjects() { List<string> projects = new List<string>(); foreach (string project in this.tdc.get_VisibleProjects(qcDomain)) { projects.Add(project); } return projects; } My assumption is that something gets retained in memory. If I run the EXE outside of VStudio it closes - but who knows what gets left behind in memory? My question is - how do I get rid of whatever calling this property returns? Shouldn't the GC handle this? Do I need to delve into pointers? Things I've tried: getting the list into a variable and setting it to null at the end of the function Adding a destructor to the class and nulling the tdc object Stepping through the tester function application all the way out, whne the form closes and the Main function ends - it closes, but VStudio still shows I'm running. Thanks for your assistance!

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• Ruby and public_method_defined? : strange behaviour

  - by aXon

  Hi there Whilst reading through the book "The well grounded Rubyist", I came across some strange behaviour. The idea behind the code is using one's own method_missing method. The only thing I am not able to grasp is, why this code gets executed, as I do not have any Person.all_with_* class methods defined, which in turn means that the self.public_method_defined?(attr) returns true (attr is friends and then hobbies). #!/usr/bin/env ruby1.9 class Person PEOPLE = [] attr_reader :name, :hobbies, :friends def initialize(mame) @name = name @hobbies = [] @friends = [] PEOPLE << self end def has_hobby(hobby) @hobbies << hobby end def has_friend(friend) @friends << friend end def self.method_missing(m,*args) method = m.to_s if method.start_with?("all_with_") attr = method[9..-1] if self.public_method_defined?(attr) PEOPLE.find_all do |person| person.send(attr).include?(args[0]) end else raise ArgumentError, "Can't find #{attr}" end else super end end end j = Person.new("John") p = Person.new("Paul") g = Person.new("George") r = Person.new("Ringo") j.has_friend(p) j.has_friend(g) g.has_friend(p) r.has_hobby("rings") Person.all_with_friends(p).each do |person| puts "#{person.name} is friends with #{p.name}" end Person.all_with_hobbies("rings").each do |person| puts "#{person.name} is into rings" end The output is is friends with is friends with is into rings which is really understandable, as there is nothing to be executed.

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• LINQ Joins - Performance

  - by Meiscooldude

  I am curious on how exactly LINQ (not LINQ to SQL) is performing is joins behind the scenes in relation to how Sql Server performs joins. Sql Server before executing a query, generates an Execution Plan. The Execution Plan is basically an Expression Tree on what it believes is the best way to execute the query. Each node provides information on whether to do a Sort, Scan, Select, Join, ect. On a 'Join' node in our execution plan, we can see three possible algorithms; Hash Join, Merge Join, and Nested Loops Join. Sql Server will choose which algorithm to for each Join operation based on expected number of rows in Inner and Outer tables, what type of join we are doing (some algorithms don't support all types of joins), whether we need data ordered, and probably many other factors. Join Algorithms: Nested Loop Join: Best for small inputs, can be optimized with ordered inner table. Merge Join: Best for medium to large inputs sorted inputs, or an output that needs to be ordered. Hash Join: Best for medium to large inputs, can be parallelized to scale linearly. LINQ Query: DataTable firstTable, secondTable; ... var rows = from firstRow in firstTable.AsEnumerable () join secondRow in secondTable.AsEnumerable () on firstRow.Field<object> (randomObject.Property) equals secondRow.Field<object> (randomObject.Property) select new {firstRow, secondRow}; SQL Query: SELECT * FROM firstTable fT INNER JOIN secondTable sT ON fT.Property = sT.Property Sql Server might use a Nested Loop Join if it knows there are a small number of rows from each table, a merge join if it knows one of the tables has an index, and Hash join if it knows there are a lot of rows on either table and neither has an index. Does Linq choose its algorithm for joins? or does it always use one?

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• LINQ to SQL: Reusable expression for property?

  - by coenvdwel

  Pardon me for being unable to phrase the title more exact. Basically, I have three LINQ objects linked to tables. One is Product, the other is Company and the last is a mapping table Mapping to store what Company sells which products and by which ID this Company refers to this Product. I am now retrieving a list of products as follows: var options = new DataLoadOptions(); options.LoadWith<Product>(p => p.Mappings); context.LoadOptions = options; var products = ( from p in context.Products select new { ProductID = p.ProductID, //BackendProductID = p.BackendProductID, BackendProductID = (p.Mappings.Count == 0) ? "None" : (p.Mappings.Count > 1) ? "Multiple" : p.Mappings.First().BackendProductID, Description = p.Description } ).ToList(); This does a single query retrieving the information I want. But I want to be able to move the logic behind the BackendProductID into the LINQ object so I can use the commented line instead of the annoyingly nested ternary operator statements for neatness and re-usability. So I added the following property to the Product object: public string BackendProductID { get { if (Mappings.Count == 0) return "None"; if (Mappings.Count > 1) return "Multiple"; return Mappings.First().BackendProductID; } } The list is still the same, but it now does a query for every single Product to get it's BackendProductID. The code is neater and re-usable, but the performance now is terrible. What I need is some kind of Expression or Delegate but I couldn't get my head around writing one. It always ended up querying for every single product, still. Any help would be appreciated!

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• How use unobtrusive validation without a model

  - by Ross Cyrus

  i have simple a form wich made by htmlHelper(mvc3) then inside of it i have 2 input field 1:type=text 2:type=submit to submit the form. there is no model behind.so i need to perfom a clientside validation on the textfield before submit it to the server.but i dont know how. i tried this puting manualy the 'data-* artibute , but does not work : @using( Html.BeginForm()) { <label for="UserName" >User Name</label> <div class="editor-field"> <input type="text" data-val="true" data-val-requierd="You must provide an user Name" id="userName" name="userName" placeholder="Enter Your User Name" /> </div> <input type="submit" value="Recover" /> } the "jquery.validate.min.js" and jquery.validate.unobtrusive.min.js and jquery.validate.min.js and jquery.validate.unobtrusive.min.js are loaded to the page. It doesnt let me to answer my self ,so i put it here : I solve it my self,just made an other view wich has its own model and Required on its propertyis and then just copy the renderd html to my own,and i got this and works : <input data-val="true" data-val-required="You must provide an user Name" id="UserName" name="UserName" type="text" value="" placeholder="Enter your User Name"/> <span class="field-validation-valid" data-valmsg-for="UserName" data-valmsg-replace="true"></span> And there is no type="Required".any way thank you guys.

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• How do actually castings work at the CLR level?

  - by devoured elysium

  When doing an upcast or downcast, what does really happen behind the scenes? I had the idea that when doing something as: string myString = "abc"; object myObject = myString; string myStringBack = (string)myObject; the cast in the last line would have as only purpose tell the compiler we are safe we are not doing anything wrong. So, I had the idea that actually no casting code would be embedded in the code itself. It seems I was wrong: .maxstack 1 .locals init ( [0] string myString, [1] object myObject, [2] string myStringBack) L_0000: nop L_0001: ldstr "abc" L_0006: stloc.0 L_0007: ldloc.0 L_0008: stloc.1 L_0009: ldloc.1 L_000a: castclass string L_000f: stloc.2 L_0010: ret Why does the CLR need something like castclass string? There are two possible implementations for a downcast: You require a castclass something. When you get to the line of code that does an castclass, the CLR tries to make the cast. But then, what would happen had I ommited the castclass string line and tried to run the code? You don't require a castclass. As all reference types have a similar internal structure, if you try to use a string on an Form instance, it will throw an exception of wrong usage (because it detects a Form is not a string or any of its subtypes). Also, is the following statamente from C# 4.0 in a Nutshell correct? Upcasting and downcasting between compatible reference types performs reference conversions: a new reference is created that points to the same object. Does it really create a new reference? I thought it'd be the same reference, only stored in a different type of variable. Thanks

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• Type result with Ternary operator in C#

  - by Vaccano

  I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be. Below is an example that I have contrived to show the issue I am having: class Program { public static void OutputDateTime(DateTime? datetime) { Console.WriteLine(datetime); } public static bool IsDateTimeHappy(DateTime datetime) { if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0) return true; return false; } static void Main(string[] args) { DateTime myDateTime = DateTime.Now; OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime); Console.ReadLine(); ^ } | } | // This line has the compile issue ---------------+ On the line indicated above, I get the following compile error: Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime' I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that. I was under the impression that: condition ? first_expression : second_expression; was the same as: if (condition) first_expression; else second_expression; Clearly this is not the case. What is the reasoning behind this? (NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it? As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)

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• CSS- How to align background image over bottom border line? Jsfiddle included

  - by John Robinson

  I have an image I am trying to display over the top of a bottom border, but it is being arranged behind the bottom border element (in this example, named "divider"), and I can't get it to align correctly. I would like the image to be displayed in the middle of the the border element and over the top of it. Vertically, I am trying to get the 1px line on the left and right side of the image to align with the 1px border to appear as if it is one element. Here is the code: .divider { border-bottom: 1px solid #c3c3c3; clear: both; display: block; margin-bottom: 20px; padding-top: 20px; width: 100%; } .sidearrow { background: url(http://s16.postimage.org/sbf7v9n75/sidearrow.png) 50% 14px no-repeat; width: 100%; height: 25px; }? <p>Here is some content above</p> <div class="sidearrow"></div> <div class="divider"></div> <p>Here is some content below</p>? And the jsfiddle: http://jsfiddle.net/F5xjx/2/ Any ideas how to get this to work? Thanks in advance.

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