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  • How to check for undefined or null variable in javascript

    - by Thomas Wanner
    We are frequently using the following code pattern in our javascript code if(typeof(some_variable) != 'undefined' && some_variable != null) { // do something with some_variable } and I'm wondering whether there is a less verbose way of checking that has the same effect. According to some forums and literature saying simply if(some_variable) { // do something with some_variable } should have the same effect. Unfortunately, Firebug evaluates such a statement as error on runtime when some_variable is undefined, whereas the first one is just fine for him. Is this only an (unwanted) behavior of Firebug or is there really some difference between those two ways ?

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  • Why are there magic attributes exposed in the Servlet spec?

    - by Brabster
    It's always seemed a little at odds with the principles of Java that the Java Servlet Spec (2.5 version here) includes a set of magic attributes containing info about included resources, namely: javax.servlet.include.request_uri javax.servlet.include.context_path javax.servlet.include.servlet_path javax.servlet.include.path_info javax.servlet.include.query_string It's not even specifically pointed out in the API documentation, only in the spec where it is a must for correct implementation. This approach feels very wrong, an exposed implementation detail that clients will use and depend on. Why is this information exposed in this way?

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  • Are protected constructors considered good practice?

    - by Álvaro G. Vicario
    I'm writing some little helper classes to handle trees. Basically, I have a node and a special root node that represents the tree. I want to keep it generic and simple. This is part of the code: <?php class Tree extends TreeNode{ public function addById($node_id, $parent_id, $generic_content){ if( $parent = $this->findNodeById($parent_id) ){ $parent->addChildById($node_id, $generic_content); } } } class TreeNode{ public function __construct($node_id, $parent_id, $generic_content){ // ... } protected function addChildById($node_id, $generic_content){ $this->children[] = new TreeNode($this->node_id, $node_id, $generic_content); } } $Categories = new Tree; $Categories->addById(1, NULL, $foo); $Categories->addById(2, NULL, $bar); $Categories->addById(3, 1, $gee); ?> My questions: Is it sensible to force TreeNode instances to be created through TreeNode::addById()? If it's so, would it be good practise to declare TreeNode::__construct() as private/protected?

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  • Me As Child Type In General Function

    - by Steven
    I have a MustInherit Parent class with two Child classes which Inherit from the Parent. How can I use (or Cast) Me in a Parent function as the the child type of that instance? EDIT: My actual goal is to be able to serialize (BinaryFormatter.Serialize(Stream, Object)) either of my child classes. However, "repeating the code" in each child "seems" wrong. EDIT2: This is my Serialize function. Where should I implement this function? Copying and pasting to each child doesn't seem right, but casting the parent to a child doesn't seem right either. Public Function Serialize() As Byte() Dim bFmt As New BinaryFormatter() Dim mStr As New MemoryStream() bFmt.Serialize(mStr, Me) Return mStr.ToArray() End Function

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  • Is Area what I am looking for?

    - by Dejan.S
    Hi I'm new to MVC2 or MVC in general. I'm gone do basic app with a backend. Now I been thinking about how I should do with the folders, views, controllers & routes for the AdminFolder. Now I just saw something called Areas. Is that a way to go for me?

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  • Using static strings to define input field names in JSPs - good idea or not?

    - by Derek Clarkson
    Hi all, I've just be asked to work on a large portal project and have been looking through the established code. I keep finding this in the jsps: <input class="portlet-form-button" name="<%=ModifyUserProfile.FORM_FIRST_TIME_LOGIN_SUBMIT%>" type="submit" ... The authors are using static strings defined in classes to define the names of input fields and buttons in jsp forms. I've never seen this done before and was wondering if this is common practice. I'm inclined to think not, but I'm asking because, apart from centralising names which I would have thought are not likely to change, I can't see the reason why. Any thoughts on this?

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  • Best way to map/join two autogenerated enums

    - by tomlip
    What is the best C++ (not C++11) way of joining two enums from autogenerated class similar to one presented below: namespace A { namespace B { ... class CarInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } class BikeInfo { enum State { // basically same enums defined in different classes Running, Stopped, Broken } } } } What is needed is unified enum State for both classes that is seen to outside world alongside with safe type conversion. The best and probably most straightforward way I came up with is to create external enum: enum State { Running, Stopped, Broken } together with conversion functions State stateEnumConv(A::B::CarInfo::State aState); State stateEnumConv(A::B::BikeInfo::State aState); A::B::CarInfo::State stateEnumConv(State aState); A::B::BikeInfo::State stateEnumConv(State aState); Direction into right approach is needed. Gosh coming from C I hate those long namespaces everywhere an I wish it could be only A::B level like in presented example. Four conversion functions seem redundant note that CarInfo::State and BikeInfo::State has same enum "members".

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  • TCP Message Structure with XML

    - by metdos
    Hello Everybody, I'm sending messages over TCP/IP and on the other side I parse TCP message.For example this is one of the sent messages. $DKMSG(requestType=REQUEST_LOGIN&requestId=123&username=metdos&password=123)$EDKMSG Clarification: $DKMSG( //Start )$EDKMSG //End requestType //Parameter REQUEST_LOGIN //Parameter Value Now I also want to add an Xml file to my message. I'm considering this option: $DKMSG(requestType=REQUEST_LOGIN&xmlData= <Item id="56D@MIT" type="SIGNAL"> <Label> <Text>56D</Text> <X1>10</X1> <Y1>40</Y1> <RotateAngle>90</RotateAngle> </Label> <X1>0</X1> <Y1>20</Y1> <Width>35</Width> <Height>10</Height> <Source>sgs3lr</Source> </Item> )$EDKMSG There are problems with this way: 1-)It doesn't seem right to me. 2-)I have to handle delimeter "=" with much more care or I need to change it in parameters. What are your suggestions, thanks.

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  • Correct structure and way of website versioning

    - by Saif Bechan
    Recently I use GIT to version my website. It makes it all really easy to see how my project develops and I always have save backups on different places on the web. Now my main question is if it is recommended to version your whole root of the website. I have a basic structure that looks something like this: /httpdocs /config /media /application index.php .htaccess 1) Should I use the /httpdocs folder to version, or should I use the content of the folder. 2) Is it recommended to version the media folder. In the media version I have several images for the overall layout, and some other images for the website. These imagas can be quite large. I work on these images from time to time and so they change. I hardly never need the old image again, so is this not just taking up precious storage space. I would highly appreciate just some basic recommendation on this topic.

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  • To "null" or not to "null" my class's attributes

    - by Helper Method
    When I write a class in Java, I like to initialize the attributes which are set to a default value directly and attributes which are set by the caller in the constructor, something like this: public class Stack<E> { private List<E> list; private size = 0; public Stack(int initialCapacity) { list = new ArrayList<E>(initialCapacity); } // remainder omitted } Now suppose I have a Tree class: public class Tree<E> { private Node<E> root = null; // no constructor needed, remainder omitted } Shall I set the root attribute to null, to mark that it is set to null by default, or omit the null value?

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  • Is it better to adopt the same technologies used at work to be effective on your home projects ?

    - by systempuntoout
    Is it better to start developing an home project using the same technologies used at work to be more productive and effective? I'm not talking about a simple hello world web page but an home project with all bells and whistles that one day, maybe, you could sell on internet. This dilemma is often subject of flames between me and a friend. He thinks that if you want to make a great home-made project you need to use the same technologies used daily at work staying in the same scope too; for example, a c++ computer game programmer should develope an home-made c++ game. I'm pretty sure that developing using the same technologies used at work can be more productive at beginning, but surely less exciting and stimulating of working with other languages\ides\libraries out of your daily job. What's your opinion about that?

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  • Saving a Django form with a Many2Many field with through table

    - by PhilGo20
    So I have this model with multiple Many2Many relationship. 2 of those (EventCategorizing and EventLocation are through tables/intermediary models) class Event(models.Model): """ Event information for Way-finding and Navigator application""" categories = models.ManyToManyField('EventCategorizing', null=True, blank=True, help_text="categories associated with the location") #categories associated with the location images = models.ManyToManyField(KMSImageP, null=True, blank=True) #images related to the event creator = models.ForeignKey(User, verbose_name=_('creator'), related_name="%(class)s_created") locations = models.ManyToManyField('EventLocation', null=True, blank=True) In my view, I first need to save the creator as the request user, so I use the commit=False parameter to get the form values. if event_form.is_valid(): event = event_form.save(commit=False) #we save the request user as the creator event.creator = request.user event.save() event = event_form.save_m2m() event.save() I get the following error: *** TypeError: 'EventCategorizing' instance expected I can manually add the M2M relationship to my "event" instance, but I am sure there is a simpler way. Am I missing on something ?

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  • tutorials/books to create a plugin/module/library?

    - by fayer
    i wonder if there are tutorials/books explaining how you create a library/plugin/module for other to implement? libraries/frameworks like solr, doctrine, codeigniter etc. cause it seems that they follow the same pattern. having one "bootstrap" file to load configurations, other classes and so on. i aim to understand the basics, so i can create a such library. cause at the moment i want to code an address book that other can use. just include a bootstrap file and they are ready to use my classes (like Doctrine). recommendations of sources to learn these things of stuff? you experienced guys, how did you learn it? thanks.

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  • Generic Abstract Singleton with Custom Constructor in C#

    - by Heka
    I want to write a generic singleton with an external constructor. In other words the constructor can be modified. I have 2 designs in my mind but I don't know whether they are practical or not. First one is to enforce derived class' constructor to be non-public but I do not know if there is a way of it? Second one is to use a delegate and call it inside the constructor? It isn't necessarily to be a constructor. The reason I chose custom constructor is doing some custom initializations. Any suggestions would be appreciated :)

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  • Where to store global variables like file paths in java ?

    - by Jules Olléon
    In my application I use some icons. Where should I store the path of the directory containing those icons ? The icons are used in different classes so it doesn't really make sense to store them in one of those classes in particular. I read that global variables are evil, but is it acceptable to use a class (eg Commons) containing only public static final fields to store this king of data ? What solution is used in professional applications ?

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  • typeof === "undefined" vs. != null

    - by Thor Thurn
    I often see JavaScript code which checks for undefined parameters etc. this way: if (typeof input !== "undefined") { // do stuff } This seems kind of wasteful, since it involves both a type lookup and a string comparison, not to mention its verbosity. It's needed because 'undefined' could be renamed, though. My question is: How is that code any better than this approach: if (input != null) { // do stuff } As far as I know, you can't redefine null, so it's not going to break unexpectedly. And, because of the type-coercion of the != operator, this checks for both undefined and null... which is often exactly what you want (e.g. for optional function parameters). Yet this form does not seem widespread, and it even causes JSLint to yell at you for using the evil != operator. Why is this considered bad style?

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  • read files from directory and filter files from Java

    - by Adnan
    The following codes goes through all directories and sub-directories and outputs just .java files; import java.io.File; public class DirectoryReader { private static String extension = "none"; private static String fileName; public static void main(String[] args ){ String dir = "C:/tmp"; File aFile = new File(dir); ReadDirectory(aFile); } private static void ReadDirectory(File aFile) { File[] listOfFiles = aFile.listFiles(); if (aFile.isDirectory()) { listOfFiles = aFile.listFiles(); if(listOfFiles!=null) { for(int i=0; i < listOfFiles.length; i++ ) { if (listOfFiles[i].isFile()) { fileName = listOfFiles[i].toString(); int dotPos = fileName.lastIndexOf("."); if (dotPos > 0) { extension = fileName.substring(dotPos); } if (extension.equals(".java")) { System.out.println("FILE:" + listOfFiles[i] ); } } if(listOfFiles[i].isDirectory()) { ReadDirectory(listOfFiles[i]); } } } } } } Is this efficient? What could be done to increase the speed? All ideas are welcome.

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  • How to handle too many files in Qt

    - by mree
    I'm not sure how to ask this, but here goes the question: I'm migrating from J2SE to Qt. After creating some small applications in Qt, I noticed that I've created way too many files compared to what I would've create if I was developing in Java (I use Netbeans). For an example, for a GUI to Orders, I'd have to create Main Order Search Window Edit Order Dialog Manage Order Dialog Maybe some other dialogs... For Java, I don't have to create a new file for every new Dialog, the Dialog will be created in the JFrame class itself. So, I will only be seeing 1 file for Orders which has other Dialogs in it. However, in Qt, I'd have to create 1 ui file, 1 header file, 1 cpp file for each of the Dialog (I know I can just put the cpp in the header, but it's easier to view codes in seperate files). So, in the end, I might end up with 3 (if there are 3 dialogs) x3 files = 9 files for the GUI in Qt, compared to Java which is only 1 file. I do know that I can create a GUI by coding it manually. But it seems easy on small GUIs but not some on complicated GUIs with lots of inputs, tabs and etc. So, is there any suggestion on how to minimize the file created in Qt?

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  • Displaying performance metrics in a modern web app?

    - by Charles
    We're updating our ancient internal PHP application at work. Right now, we gather extensive performance measurements on every pageview, and log them to the database. Additionally, users requested that some of the metrics be displayed at the bottom of the page. This worked out pretty well for us, because the last thing that the application does on every request is include the file containing the HTML footer. The updated parts of the application use an MVC framework and a Dispatch/Request/Response loop. The page footer is no longer the last thing done. In fact, it could very well be the first thing done, before the rest of the page is created. Because we can grab the Response before it's returned to the user, we could try to include placeholders for the performance metrics in the footer and simply replace them with the actual numbers, but this strikes me as a bad idea somehow. How do you handle this in your modern web app? While we're using PHP, I'm curious how it's done in a Ruby/Rails app, and in your favorite Python framework.

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  • ASP.NET MVC Filters: How to set Viewdata for Dropdown based on action paramter

    - by CRice
    Hi, Im loading an entity 'Member' from its id in route data. [ListItemsForMembershipType(true)] public ActionResult Edit(Member someMember) {...} The attribute on the action loads the membership type list items for a dropdown box and sticks it in viewdata. This is fine for add forms, and search forms (it gets all active items) but I need the attribute to execute BASED ON THE VALUE someMember.MembershipTypeId, because its current value must always be present when loading the item (i.e. all active items, plus the one from the loaded record). So the question is, what is the standard pattern for this? How can my attribute accept the value or should I be loading the viewdata for the drop down in a controller supertype or during model binding or something else? It is in an attribute now because the code to set the viewdata would otherwise be duplicated in each usage in each action.

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