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• Fake serial communication under Linux

  - by kigurai

  I have an application where I want to simulate the connection between a device and a "modem". The device will be connected to a serial port and will talk to the software modem through that. For testing purposes I want to be able to use a mock software device to test send and receive data. Example Python code device = Device() modem = Modem() device.connect(modem) device.write("Hello") modem_reply = device.read() Now, in my final app I will just pass /dev/ttyS1 or COM1 or whatever for the application to use. But how can I do this in software? I am running Linux and application is written in Python. I have tried making a FIFO (mkfifo ~/my_fifo) and that does work, but then I'll need one FIFO for writing and one for reading. What I want is to open ~/my_fake_serial_port and read and write to that. I have also lpayed with the ptymodule, but can't get that to work either. I can get a master and slave file descriptor from pty.openpty() but trying to read or write to them only causes IOError Bad File Descriptor error message.

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• Is it possible to refer to metadata of the target from within the target implementation in MSBuild?

  - by mark

  Dear ladies and sirs. My msbuild targets file contains the following section: <ItemGroup> <Targets Include="T1"> <Project>A\B.sln"</Project> <DependsOnTargets>The targets T1 depends on</DependsOnTargets> </Targets> <Targets Include="T2"> <Project>C\D.csproj"</Project> <DependsOnTargets>The targets T2 depends on</DependsOnTargets> </Targets> ... </ItemGroup> <Target Name="T1" DependsOnTargets="The targets T1 depends on"> <MSBuild Projects="A\B.sln" Properties="Configuration=$(Configuration)" /> </Target> <Target Name="T2" DependsOnTargets="The targets T2 depends on"> <MSBuild Projects="C\D.csproj" Properties="Configuration=$(Configuration)" /> </Target> As you can see, A\B.sln appears twice: As Project metadata of T1 in the ItemGroup section. In the Target statement itself passed to the MSBuild task. I am wondering whether I can remove the second instance and replace it with the reference to the Project metadata of the target, which name is given to the Target task? Exactly the same question is asked for the (Targets.DependsOnTargets) metadata. It is mentioned twice much like the %(Targets.Project) metadata. Thanks. EDIT: I should probably describe the constraints, which must be satisfied by the solution: I want to be able to build individual projects with ease. Today I can simply execute msbuild file.proj /t:T1 to build the T1 target and I wish to keep this ability. I wish to emphasize, that some projects depend on others, so the DependsOnTargets attribute is really necessary for them.

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• Strange problem with PHP and sessions

  - by Jhorra

  So the basis of this page is I set a session value when the page loads, and clear it on any other page they visit. Then the page can make an ajax call to download a file. If the session value matches the value I pass through the URL I allow them to download the file. If not I return a 404 error. I was having some weird issues, so I removed the 404 and set it to echo out the values instead to see what I was getting. Here is the top of the code on the page: $code = $this->_request->getParam('code'); $confirm = $_SESSION['mp3_code']; echo $code."-1-".$confirm; if($code != $confirm) echo $code."-2-".$confirm;//header("HTTP/1.1 404 Not Found"); else { Here is what displays on the page from the ajax call 12723430-1-12723430-2- As you can see when it echos out the first time they exist, then somehow after I compare them and it fails you see that it echos out blank values like they suddenly ceased to exist. Any ideas?

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• PHP Exceptions in Classes

  - by mike condiff

  I'm writing a web application (PHP) for my friend and have decided to use my limited OOP training from Java. My question is what is the best way to note in my class/application that specific critical things failed without actually breaking my page. Currently my problem is I have an Object "SummerCamper" which takes a camper_id as it's argument to load all of the necessary data into the object from the database. Say someone specifies a camper_id in the querystring that does not exist, I pass it to my objects constructor and the load fails. Currently I don't see a way for me to just return false from the constructor. I have read I could possibly do this with Exceptions, throwing an exception if no records are found in the database or if some sort of validation fails on input of the camper_id from the application etc. However, I have not really found a great way to alert my program that the Object Load has failed. I tried returning false from within the CATCH but the Object still persists in my php page. I do understand I could put a variable $is_valid = false if the load fails and then check the Object using a get method but I think there may be better ways. What is the best way of achieving the essential termination of an object if a load fails? Should I load data into the object from outside the constructor? Is there some osrt of design pattern that I should look into? Any help would be appreciated.

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• Change nhibernate config with nant xmlpoke

  - by isuruceanu

  Hi All How can I change the connection string from nhibernate.config file using nant the problem is that all examples are about changing attribute value, but nhibernate has inner text eq: <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2"> <session-factory> <property name="connection.connection_string">Data Source.\server;Database=UnitTestDb;UID=user;pwd=pass;</property> <property name="dialect">NHibernate.Dialect.MsSql2008Dialect</property> <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property> <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property> <property name="show_sql">true</property> <property name="connection.release_mode">auto</property> <property name="adonet.batch_size">500</property> .... I need to change property connection.connection_string <xmlpoke file="${nhibernate.file}" xpath="/hibernate-configuration/session-factory/add[@key='connection.connection_string']/@value" value="${connection.string}"> </xmlpoke> this does not work in this case. Thanks

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• Passing an array of structs in C

  - by lelouch

  I'm having trouble passing an array of structs to a function in C. I've created the struct like this in main: int main() { struct Items { char code[10]; char description[30]; int stock; }; struct Items MyItems[10]; } I then access it like: MyItems[0].stock = 10; etc. I want to pass it to a function like so: ReadFile(MyItems); The function should read the array, and be able to edit it. Then I should be able to access the same array from other functions. I've tried heaps of declarations but none of them work. e.g. void ReadFile(struct Items[10]) I've had a look around for other questions, but the thing is they're all done different, with typedefs and asterisks. My teacher hasn't taught us pointers yet, so I'd like to do it with what I know. Any ideas? :S EDIT: Salvatore's answer is working after I fixed my prototype to: void ReadFile(struct Items[9]);

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• Update Options on Existing jQuery Object

  - by Vince Kronlein

  I'm using Bootstrap and DataTables in my app and I have a default initializer for tables based on class. I can just add the class data-table to the table and it gets instantiated with the default values I want. I'd like to know how to change or update specific options based on a specific table. if ($.fn.dataTable) { $('.data-table').dataTable( { sDom: "R<'row'<'span6'l><'span6'f>r>t<'row'<'span6'i><'span6'p>>", sPaginationType: "bootstrap", oLanguage: { "sLengthMenu": "_MENU_ &nbsp; records per page" }, aoColumnDefs: [ { "bSortable": false, "aTargets": [ 0 ] } ] }); } All my data tables have a checkbox in the first column so the above removal of sorting works for all of them. But I'd like to be able to update the aoColumnDefs on a table by table basis so I can add other columns that I don't want sorted. So let's say I have a table: $('#member-list'), how do I access this object and update it's datatables options in jQuery? I can't find any reference or help anywhere. Thanks a lot! -V

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• Passing Values to Controllers

  - by Dru

  I'm trying to allow users to 'favorite' links (that is, create a new Favorite record with their user_id and the link_id) This is what I have so far.. When I click favorite (as a user), the new record is assigned to the user_id but the link_id field is nil. How can I pass the link_id into my FavoritesController? My View Code Added Link Model Code class FavoritesController < ApplicationController def create @user = User.find(session[:user_id]) @favorite = @user.favorites.create :link_id => params[:id] redirect_to :back end end The Favorite model belongs to :user and :link Note: I've also tried this but when I click 'favorite', there's an error "Couldn't find Link without an ID." Update <%= link_to "Favorite", :controller => :favorites, :action => :create, :link_id => link.id %> with class FavoritesController < ApplicationController def create @user = User.find(session[:user_id]) @favorite = @user.favorites.create :link_id => :params[:link_id] redirect_to :back end end Returns "can't convert Symbol into Integer" app/controllers/favorites_controller.rb:4:in [] app/controllers/favorites_controller.rb:4:in create I've tried forcing it into an Integer several ways with .to_i

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• NHibernate / Fluent - Mapping multiple objects to single lookup table

  - by Al

  Hi all I am struggling a little in getting my mapping right. What I have is a single self joined table of look up values of certain types. Each lookup can have a parent, which can be of a different type. For simplicities sake lets take the Country and State example. So the lookup table would look like this: Lookups Id Key Value LookupType ParentId - self joining to Id base class public class Lookup : BaseEntity { public Lookup() {} public Lookup(string key, string value) { Key = key; Value = value; } public virtual Lookup Parent { get; set; } [DomainSignature] [NotNullNotEmpty] public virtual LookupType LookupType { get; set; } [NotNullNotEmpty] public virtual string Key { get; set; } [NotNullNotEmpty] public virtual string Value { get; set; } } The lookup map public class LookupMap : IAutoMappingOverride<DBLookup> { public void Override(AutoMapping<Lookup> map) { map.Table("Lookups"); map.References(x => x.Parent, "ParentId").ForeignKey("Id"); map.DiscriminateSubClassesOnColumn<string>("LookupType").CustomType(typeof(LookupType)); } } BASE SubClass map for subclasses public class BaseLookupMap : SubclassMap where T : DBLookup { protected BaseLookupMap() { } protected BaseLookupMap(LookupType lookupType) { DiscriminatorValue(lookupType); Table("Lookups"); } } Example subclass map public class StateMap : BaseLookupMap<State> { protected StateMap() : base(LookupType.State) { } } Now I've almost got my mappings set, however the mapping is still expecting a table-per-class setup, so is expecting a 'State' table to exist with a reference to the states Id in the Lookup table. I hope this makes sense. This doesn't seem like an uncommon approach when wanting to keep lookup-type values configurable. Thanks in advance. Al

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• Macports and virtualenv site-packages Fallback

  - by Streeter

  I've installed django and python as this link suggested with macports. However, I'd like to use virtualenv to install more packages. My understanding is that if I do not pass in the --no-site-packages to virtualenv, I should get the currently installed packages in addition to whatever packages I install into the virtual environment. Is this correct? As an example, I've installed django through macports and then create a virtual environment, but I cannot import django from within that virtual environment: [streeter@mordecai]:~$ mkvirtualenv django-test New python executable in django-test/bin/python Installing setuptools............done. ... (django-test)[streeter@mordecai]:~$ pip install django-debug-toolbar Downloading/unpacking django-debug-toolbar Downloading django-debug-toolbar-0.8.4.tar.gz (80Kb): 80Kb downloaded Running setup.py egg_info for package django-debug-toolbar Installing collected packages: django-debug-toolbar Running setup.py install for django-debug-toolbar Successfully installed django-debug-toolbar Cleaning up... (django-test)[streeter@mordecai]:~$ python Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49) [GCC 4.2.1 (Apple Inc. build 5646)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import django Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: No module named django >>> So I can install packages into the virtual environment, but it isn't picking up the global site-packages. Or am I not doing something correctly / missing something / misunderstanding how virtualenv works? I've got Mac OS 10.6 (Snow Leopard), have updated my macports packages and am using macports' python26 (via python_select python26).

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• erlide, which eclipse/which packages?

  - by KevinDTimm

  I have downloaded eclipse 3.4 (java version) for MacOSX (carbon). I have tried to 'update' to the erlide, but see many (duplicated) options (many erlide, options that say 'only for erl SDK updates', etc.) Sometimes I get 403 errors when attempting to access http://erlide.org/update and http://erlide.sourceforge.net/update. Finally, when I get some set of options installed, I either get errors like : Loading of /Users/kevindtimm/Documents/eclipse-java-ganymede-SR2-macosx-carbon/eclipse/plugins/org.erlide.kernel.common_0.8.1.201005250801/ebin/erlide_kernel_common.beam failed: badfile (hello_world@ktmac)1> =ERROR REPORT==== 24-Nov-2010::19:17:32 === beam/beam_load.c(1768): Error loading function erlide_kernel_common:monitor/0: op put_string u u x: please re-compile this module with an R14B compiler or, when I've done different installations of erlide, I get no response in the console to : hello:hello(). Does anybody have a good reference for how to load this plug-in and which items I should install? -module(hello). -export([hello/0]). hello() -> io:write("Hello World\n"). [edit] I have installed eclipse 3.6 (c++) as requested below, and the following code still can't find hello:hello(). %%file_comment -module(hello). %% %% Include files %% %% %% Exported Functions %% -export([hello/0]). %% %% API Functions %% %% %% Local Functions %% hello() -> io:write("Hello World\n"). [/edit]

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• NHibernate query against the key field of a dictionary (map)

  - by Carl Raymond

  I have an object model where a Calendar object has an IDictionary<MembershipUser, Perms> called UserPermissions, where MembershipUser is an object, and Perms is a simple enumeration. This is in the mapping file for Calendar as <map name="UserPermissions" table="CalendarUserPermissions" lazy="true" cascade="all"> <key column="CalendarID"/> <index-many-to-many class="MembershipUser" column="UserGUID" /> <element column="Permissions" type="CalendarPermission" not-null="true" /> </map> Now I want to execute a query to find all calendars for which a given user has some permission defined. The permission is irrelevant; I just want a list of the calendars where a given user is present as a key in the UserPermissions dictionary. I have the username property, not a MembershipUser object. How do I build that using QBC (or HQL)? Here's what I've tried: ISession session = SessionManager.CurrentSession; ICriteria calCrit = session.CreateCriteria<Calendar>(); ICriteria userCrit = calCrit.CreateCriteria("UserPermissions.indices"); userCrit.Add(Expression.Eq("Username", username)); return calCrit.List<Calendar>(); This constructed invalid SQL -- the WHERE clause contained WHERE membership1_.Username = @p0 as expected, but the FROM clause didn't include the MemberhipUsers table. Also, I really had to struggle to learn about the .indices notation. I found it by digging through the NHibernate source code, and saw that there's also .elements and some other dotted notations. Where's a reference to the allowed syntax of an association path? I feel like what's above is very close, and just missing something simple.

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• $HTTP_RAW_POST_DATA and Wordpress media_handle_upload

  - by BaronVonKaneHoffen

  Hi there! So I'm making something for which users need to upload images from a canvas element (on the front end) using Wordpress's in-built Media Upload API. I've successfully uploaded images with the API from a file input in a form: <input type="file" name="async-upload" id="async-upload" size="40" /> ... <?php $new_attach_id = media_handle_upload( 'async-upload', $new_id ); ?> and I've saved images from the canvas using my own script: <script type="text/javascript"> ... var img = canvas.toDataURL("image/png"); ... ajax.send(img ); </script> ... <?php $imageData=$GLOBALS['HTTP_RAW_POST_DATA']; $filteredData=substr($imageData, strpos($imageData, ",")+1); $unencodedData=base64_decode($filteredData); $fp = fopen( 'saved_images/canv_save_test.png', 'wb' ); fwrite( $fp, $unencodedData); ... ?> Problem is, Wordpress's media_handle_upload() only accepts an index to the $_FILES array for the upload. So the question is: How can I pass the image data from HTTP_RAW_POST_DATA to it? Could I make the $_FILES['tmp-name'] point to it somehow? Could I use another script as an intermediate step somehow? Could I unleash the monkeys on the typewriter until they come up with the answer? Any help very very much appreciated! Thanks, Kane

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• How safe and reliable are C++ String Literals?

  - by DoctorT

  So, I'm wanting to get a better grasp on how string literals in C++ work. I'm mostly concerned with situations where you're assigning the address of a string literal to a pointer, and passing it around. For example: char* advice = "Don't stick your hands in the toaster."; Now lets say I just pass this string around by copying pointers for the duration of the program. Sure, it's probably not a good idea, but I'm curious what would actually be going on behind the scenes. For another example, let's say we make a function that returns a string literal: char* foo() { // function does does stuff return "Yikes!"; // somebody's feeble attempt at an error message } Now lets say this function is called very often, and the string literal is only used about half the time it's called: // situation #1: it's just randomly called without heed to the return value foo(); // situation #2: the returned string is kept and used for who knows how long char* retVal = foo(); In the first situation, what's actually happening? Is the string just created but not used, and never deallocated? In the second situation, is the string going to be maintained as long as the user finds need for it? What happens when it isn't needed anymore... will that memory be freed up then (assuming nothing points to that space anymore)? Don't get me wrong, I'm not planning on using string literals like this. I'm planning on using a container to keep my strings in check (probably std::string). I'm mostly just wanting to know if these situations could cause problems either for memory management or corrupted data.

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• ASP.NEt MVC 2 application error on IIS7 works fine on local machine

  - by aspCoolguy

  My ASP.NET MVC2 application is developed using 1. VS 2010 2. Linq To SQL for Models Here is Call controller code: namespace CallTrackMVC.Controllers { public class CallController : Controller { private CallTrackRepository repository; public CallController():this(new CallTrackRepository()) { } public CallController(CallTrackRepository newRepository) { repository = newRepository; } } } Error on IIS7 when browsing the Call Create page is NullReferenceException: Object reference not set to an instance of an object.] CallTrackMVC.Models.ExecOfficeDataContext..ctor() in C:\ClearCase\rartadi_view\STS_Dev_TEST\CallTrackMVC\Models\ExecOffice.designer.cs:71 CallTrackMVC.Controllers.CallController..ctor() in C:\ClearCase\rartadi_view\STS_Dev_TEST\CallTrackMVC\Controllers\CallController.cs:16 [TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +117 System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +247 System.Activator.CreateInstance(Type type, Boolean nonPublic) +106 System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +102 [InvalidOperationException: **An error occurred when trying to create a controller of type 'CallTrackMVC.Controllers.CallController'. Make sure that the controller has a parameterless public constructor.**] System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +541 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +85 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +165 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +80 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +389 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +371 Code in Global.asax is protected void Application_Start() { AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes); } Any suggestion would be a great help.

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• JVM GC demote object to eden space?

  - by Kevin

  I'm guessing this isn't possible...but here goes. My understanding is that eden space is cheaper to collect than old gen space, especially when you start getting into very large heaps. Large heaps tend to come up with long running applications (server apps) and server apps a lot of the time want to use some kind of caches. Caches with some kind of eviction (LRU) tend to defeat some assumptions that GC makes (temporary objects die quickly). So cache evictions end up filling up old gen faster than you'd like and you end up with a more costly old gen collection. Now, it seems like this sort of thing could be avoided if java provided a way to mark a reference as about to die (delete keyword)? The difference between this and c++ is that the use is optional. And calling delete does not actually delete the object, but rather is a hint to the GC that it should demote the object back to Eden space (where it will be more easily collected). I'm guessing this feature doesn't exist, but, why not (is there a reason it's a bad idea)?

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• OOP, Interface Design and Encapsulation

  - by Mau

  C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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• IE8 removes background-color of header row of Asp:Gridview

  - by Hitesh Riziya

  I am using Asp.net 4.0 GridView control to display data from database. I have applied the inbuilt theme to GridView. <asp:GridView ID="gv" runat="server" CellPadding="4" EmptyDataText="No records found." ForeColor="#333333" OnRowCommand="gv_RowCommand" Width="99%" OnPageIndexChanging="gv_PageIndexChanged" PageSize="50" AllowPaging="True" GridLines="None" AutoGenerateColumns="true"> <AlternatingRowStyle BackColor="White" /> <EditRowStyle BackColor="#7C6F57" /> <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" /> <HeaderStyle CssClass="GridHeader" BackColor="#1C5E55" Font-Bold="True" ForeColor="White" HorizontalAlign="Left" /> <PagerStyle BackColor="#666666" ForeColor="White" HorizontalAlign="Center" /> <RowStyle BackColor="#E3EAEB" /> <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" /> <SortedAscendingCellStyle BackColor="#F8FAFA" /> <SortedAscendingHeaderStyle BackColor="#246B61" /> <SortedDescendingCellStyle BackColor="#D4DFE1" /> <SortedDescendingHeaderStyle BackColor="#15524A" /></asp:GridView> I tried setting the CSS forcefully in my Master page .GridHeader { background-color:#1C5E55 !important;} But I am still missing the background-color. I can see the backgroundcolor applied to grid (for less-than 1 sec) while the page loading the js/css content NOTE: I already tried clearing cache of IE, ctrl + F5, shift + reload etc. Here is sample page of my issue. http://vd2.weenggs.com/Items.aspx email: [email protected] pass: test Thanks

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• Add an event to HTML elements with a specific class.

  - by Juan C. Rois

  Hello everybody, I'm working on a modal window, and I want to make the function as reusable as possible. Said that, I want to set a few anchor tags with a class equals to "modal", and when a particular anchor tag is clicked, get its Id and pass it to a function that will execute another function based on the Id that was passed. This is what I have so far: // this gets an array with all the elements that have a class equals to "modal" var anchorTrigger = document.getElementsByClassName('modal'); Then I tried to set the addEventListener for each item in the array by doing this: var anchorTotal = anchorTrigger.length; for(var i = 0; i < anchorTotal ; i++){ anchorTrigger.addEventListener('click', fireModal, false); } and then run the last function "fireModal" that will open the modal, like so: function fireModal(){ //some more code here ... } My problem is that in the "for" loop, I get an error saying that anchorTrigger.addEvent ... is not a function. I can tell that the error might be related to the fact that I'm trying to set up the "addEventListener" to an array as oppose to individual elements, but I don't know what I'm supposed to do. Any help would be greatly appreciated.

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• Why do Scala maps have poor performance relative to Java?

  - by Mike Hanafey

  I am working on a Scala app that consumes large amounts of CPU time, so performance matters. The prototype of the system was written in Python, and performance was unacceptable. The application does a lot with inserting and manipulating data in maps. Rex Kerr's Thyme was used to look at the performance of updating and retrieving data from maps. Basically "n" random Ints were stored in maps, and retrieved from the maps, with the time relative to java.util.HashMap used as a reference. The full results for a range of "n" are here. Sample (n=100,000) performance relative to java, smaller is worse: Update Read Mutable 16.06% 76.51% Immutable 31.30% 20.68% I do not understand why the scala immutable map beats the scala mutable map in update performance. Using the sizeHint on the mutable map does not help (it appears to be ignored in the tested implementation, 2.10.3). Even more surprisingly the immutable read performance is worse than the mutable read performance, more significantly so with larger maps. The update performance of the scala mutable map is surprisingly bad, relative to both scala immutable and plain Java. What is the explanation?

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• Serializing Configurations for a Dependency Injection / Inversion of Control

  - by Joshua Starner

  I've been researching Dependency Injection and Inversion of Control practices lately in an effort to improve the architecture of our application framework and I can't seem to find a good answer to this question. It's very likely that I have my terminology confused, mixed up, or that I'm just naive to the concept right now, so any links or clarification would be appreciated. Many examples of DI and IoC containers don't illustrate how the container will connect things together when you have a "library" of possible "plugins", or how to "serialize" a given configuration. (From what I've read about MEF, having multiple declarations of [Export] for the same type will not work if your object only requires 1 [Import]). Maybe that's a different pattern or I'm blinded by my current way of thinking. Here's some code for an example reference: public abstract class Engine { } public class FastEngine : Engine { } public class MediumEngine : Engine { } public class SlowEngine : Engine { } public class Car { public Car(Engine e) { engine = e; } private Engine engine; } This post talks about "Fine-grained context" where 2 instances of the same object need different implementations of the "Engine" class: http://stackoverflow.com/questions/2176833/ioc-resolve-vs-constructor-injection Is there a good framework that helps you configure or serialize a configuration to achieve something like this without hard coding it or hand-rolling the code to do this? public class Application { public void Go() { Car c1 = new Car(new FastEngine()); Car c2 = new Car(new SlowEngine()); } } Sample XML: <XML> <Cars> <Car name="c1" engine="FastEngine" /> <Car name="c2" engine="SlowEngine" /> </Cars> </XML>

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• Generic version control strategy for select table data within a heavily normalized database

  - by leppie

  Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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• Is the REST support in Spring 3's MVC Framework production quality yet?

  - by glenjohnson

  Hi all, Since Spring 3 was released in December last year, I have been trying out the new REST features in the MVC framework for a small commercial project involving implementing a few RESTful Web Services which consume XML and return XML views using JiBX. I plan to use either Hibernate or JDBC Templates for the data persistence. As a Spring 2.0 developer, I have found Spring 3's (and 2.5's) new annotations way of doing things quite a paradigm shift and have personally found some of the new MVC annotation features difficult to get up to speed with for non-trivial applications - as such, I am often having to dig for information in forums and blogs that is not apparent from going through the reference guide or from the various Spring 3 REST examples on the web. For deadline-driven production quality and mission critical applications implementing a RESTful architecture, should I be holding off from Spring 3 and rather be using mature JSR 311 (JAX-RS) compliant frameworks like RESTlet or Jersey for the REST layer of my code (together with Spring 2 / 2.5 to tie things together)? I had no problems using RESTlet 1.x in a previous project and it was quite easy to get up to speed with (no magic tricks behind the scenes), but when starting my current project it initially looked like the new REST stuff in Spring 3's MVC Framework would make life easier. Do any of you out there have any advice to give on this? Does anyone know of any commercial / production-quality projects using, or having successfully delivered with, the new REST stuff in Spring 3's MVC Framework. Many thanks Glen

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• Help me write my LISP :) LISP environments, Ruby Hashes...

  - by MikeC8

  I'm implementing a rudimentary version of LISP in Ruby just in order to familiarize myself with some concepts. I'm basing my implementation off of Peter Norvig's Lispy (http://norvig.com/lispy.html). There's something I'm missing here though, and I'd appreciate some help... He subclasses Python's dict as follows: class Env(dict): "An environment: a dict of {'var':val} pairs, with an outer Env." def __init__(self, parms=(), args=(), outer=None): self.update(zip(parms,args)) self.outer = outer def find(self, var): "Find the innermost Env where var appears." return self if var in self else self.outer.find(var) He then goes on to explain why he does this rather than just using a dict. However, for some reason, his explanation keeps passing in through my eyes and out through the back of my head. Why not use a dict, and then inside the eval function, when a new "sub-environment" needs to be created, just take the existing dict and update the key/value pairs that need to be updated, and pass that new dict into the next eval? Won't the Python interpreter keep track of the previous "outer" envs? And won't the nature of the recursion ensure that the values are pulled out from "inner" to "outer"? I'm using Ruby, and I tried to implement things this way. Something's not working though, and it might be because of this, or perhaps not. Here's my eval function, env being a regular Hash: def eval(x, env = $global_env) ........ elsif x[0] == "lambda" then ->(*args) { eval(x[2], env.merge(Hash[*x[1].zip(args).flatten(1)])) } ........ end The line that matters of course is the "lambda" one. If there is a difference, what's importantly different between what I'm doing here and what Norvig did with his Env class? If there's no difference, then perhaps someone can enlighten me as to why Norvig uses the Env class. Thanks :)

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• How would I go about sharing variables in a C++ class with Lua?

  - by Nicholas Flynt

  I'm fairly new to Lua, I've been working on trying to implement Lua scripting for logic in a Game Engine I'm putting together. I've had no trouble so far getting Lua up and running through the engine, and I'm able to call Lua functions from C and C functions from Lua. The way the engine works now, each Object class contains a set of variables that the engine can quickly iterate over to draw or process for physics. While game objects all need to access and manipulate these variables in order for the Game Engine itself to see any changes, they are free to create their own variables, a Lua is exceedingly flexible about this so I don't forsee any issues. Anyway, currently the Game Engine side of things are sitting in C land, and I really want them to stay there for performance reasons. So in an ideal world, when spawning a new game object, I'd need to be able to give Lua read/write access to this standard set of variables as part of the Lua object's base class, which its game logic could then proceed to run wild with. So far, I'm keeping two separate tables of objects in place-- Lua spawns a new game object which adds itself to a numerically indexed global table of objects, and then proceeds to call a C++ function, which creates a new GameObject class and registers the Lua index (an int) with the class. So far so good, C++ functions can now see the Lua object and easily perform operations or call functions in Lua land using dostring. What I need to do now is take the C++ variables, part of the GameObject class, and expose them to Lua, and this is where google is failing me. I've encountered a very nice method here which details the process using tags, but I've read that this method is deprecated in favor of metatables. What is the ideal way to accomplish this? Is it worth the hassle of learning how to pass class definitions around using libBind or some equivalent method, or is there a simple way I can just register each variable (once, at spawn time) with the global lua object? What's the "current" best way to do this, as of Lua 5.1.4?

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