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• A simple Python deployment problem - a whole world of pain

  - by Evgeny

  We have several Python 2.6 applications running on Linux. Some of them are Pylons web applications, others are simply long-running processes that we run from the command line using nohup. We're also using virtualenv, both in development and in production. What is the best way to deploy these applications to a production server? In development we simply get the source tree into any directory, set up a virtualenv and run - easy enough. We could do the same in production and perhaps that really is the most practical solution, but it just feels a bit wrong to run svn update in production. We've also tried fab, but it just never works first time. For every application something else goes wrong. It strikes me that the whole process is just too hard, given that what we're trying to achieve is fundamentally very simple. Here's what we want from a deployment process. We should be able to run one simple command to deploy an updated version of an application. (If the initial deployment involves a bit of extra complexity that's fine.) When we run this command it should copy certain files, either out of a Subversion repository or out of a local working copy, to a specified "environment" on the server, which probably means a different virtualenv. We have both staging and production version of the applications on the same server, so they need to somehow be kept separate. If it installs into site-packages, that's fine too, as long as it works. We have some configuration files on the server that should be preserved (ie. not overwritten or deleted by the deployment process). Some of these applications import modules from other applications, so they need to be able to reference each other as packages somehow. This is the part we've had the most trouble with! I don't care whether it works via relative imports, site-packages or whatever, as long as it works reliably in both development and production. Ideally the deployment process should automatically install external packages that our applications depend on (eg. psycopg2). That's really it! How hard can it be?

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• Complex HashMap has different hashCode after serialization

  - by woezelmann

  I am parsing a xml file into a complex HashMap looking like this: Map<String, Map<String, EcmObject> EcmObject: public class EcmObject implements Comparable, Serializable { private final EcmObjectType type; private final String name; private final List<EcmField> fields; private final boolean pages; // getter, equals, hashCode } EcmObjectType: public enum EcmObjectType implements Serializable { FOLDER, REGISTER, DOCUMENT } EcmField public class EcmField implements Comparable, Serializable { private final EcmFieldDataType dataType; private final EcmFieldControlType controlType; private final String name; private final String dbname; private final String internalname; private final Integer length; // getter, equals, hashCode } EcmFieldDataType public enum EcmFieldDataType implements Serializable { TEXT, DATE, NUMBER, GROUP, DEC; } and EcmFieldControlType public enum EcmFieldControlType implements Serializable{ DEFAULT, CHECKBOX, LIST, DBLIST, TEXTAREA, HIERARCHY, TREE, GRID, RADIO, PAGECONTROL, STATIC; } I have overwritten all hashCode and equal methods by usind commons lang's EqualsBuilder and HashCodeBuilder. Now when I copy a A HashMap this way: Map<String, Map<String, EcmObject>> m = EcmUtil.convertXmlObjectDefsToEcmEntries(new File("e:\\objdef.xml")); Map<String, Map<String, EcmObject>> m2; System.out.println(m.hashCode()); ByteArrayOutputStream baos = new ByteArrayOutputStream(8 * 4096); ObjectOutputStream oos = new ObjectOutputStream(baos); oos.writeObject(m); ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray()); ObjectInputStream ois = new ObjectInputStream(bais); m2 = (Map<String, Map<String, EcmObject>>) ois.readObject(); System.out.println(m.hashCode()); System.out.println(m2.hashCode()); m.hashCode() is not equal to m2.hashCode() here is my output: -1639352210 -2071553208 1679930154 Another strange thing is, that eg. 10 times m has the same hashcode and suddenly on the 11th time the hashcode is different... Any ideas what this is about?

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• Asynchronous vs Synchronous vs Threading in an iPhone App

  - by Coocoo4Cocoa

  I'm in the design stage for an app which will utilize a REST web service and sort of have a dilemma in as far as using asynchronous vs synchronous vs threading. Here's the scenario. Say you have three options to drill down into, each one having its own REST-based resource. I can either lazily load each one with a synchronous request, but that'll block the UI and prevent the user from hitting a back navigation button while data is retrieved. This case applies almost anywhere except for when your application requires a login screen. I can't see any reason to use synchronous HTTP requests vs asynchronous because of that reason alone. The only time it makes sense is to have a worker thread make your synchronous request, and notify the main thread when the request is done. This will prevent the block. The question then is bench marking your code and seeing which has more overhead, a threaded synchronous request or an asynchronous request. The problem with asynchronous requests is you need to either setup a smart notification or delegate system as you can have multiple requests for multiple resources happening at any given time. The other problem with them is if I have a class, say a singleton which is handling all of my data, I can't use asynchronous requests in a getter method. Meaning the following won't go: - (NSArray *)users { if(users == nil) users = do_async_request // NO GOOD return users; } whereas the following: - (NSArray *)users { if(users == nil) users == do_sync_request // OK. return users; } You also might have priority. What I mean by priority is if you look at Apple's Mail application on the iPhone, you'll notice they first suck down your entire POP/IMAP tree before making a second request to retrieve the first 2 lines (the default) of your message. I suppose my question to you experts is this. When are you using asynchronous, synchronous, threads -- and when are you using either async/sync in a thread? What kind of delegation system do you have setup to know what to do when a async request completes? Are you prioritizing your async requests? There's a gamut of solutions to this all too common problem. It's simple to hack something out. The problem is, I don't want to hack and I want to have something that's simple and easy to maintain.

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• next line character a huge influence on xmlparser?

  - by jovany

  I have question about a basic xml file I'm parsing and just putting in simple nextlines(Enters). I'll try to explain my problem with this next example. I'm( still) building an xml tree and all it has to do ( this is a testtree ) is put the summary in an itemlist. I then export it to a plist so I can see if everything is done correctly. A method that does this is in the parser which looks like this if([elementName isEqualToString:@"Book"]) { [appDelegate.books addObject:aBook]; [aBook release]; aBook = nil; } else { [aBook setValue:currentElementValue forKey:elementName]; NSString *directions = [NSString stringWithFormat:currentElementValue]; [directionTree = setObject:directions forKey:@"directions"]; } [currentElementValue release]; currentElementValue = nil; } the export for the plistfile happens at the endtag of books. Below is the first xmlfile <?xml version="1.0" encoding="UTF-8"?> <Books><Book id="1"><summary>Ero adn the ancient quest to measure the globe.</summary></Book><Book id="2"><summary>how the scientific revolution began.</summary></Book></Books> This is my output http://img139.imageshack.us/img139/9175/picture6rtn.png If I make some adjustments like here <?xml version="1.0" encoding="UTF-8"?> <Books><Book id="1"> <summary>Ero adn the ancient quest to measure the globe.</summary> </Book> <Book id="2"> <summary>how the scientific revolution began.</summary> </Book> </Books> My directions key with type string remains empty... http://img248.imageshack.us/img248/5838/picture7y.png I never knew that if I just put in an enter it would have such an influence. Does anyone know a solution to this since my real xml file looks like this. ps. the funny thing is I can actually see ( when debugging)my directions string (NSString directions ) fill up with the currentElementValue in both cases.

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• Can't use attached property on combobox inside hierarchical datatemplate WPF

  - by jesse_t_r

  I'm hoping to use an attached property to assign a command to the selection changed event of a combobox that is embedded inside a treeview. I'm attempting to set the attached property inside the hierchical data template for the tree but the command is not set and does not fire when the item in the combobox is changed. I've found that setting the attached property directly on a combobox outside of a datatemplate works fine; here is how I'm trying to set the property in the template: <HierarchicalDataTemplate x:Key="template1" ItemsSource="{Binding Path=ChildColumns}"> <Border Background="{StaticResource TreeItem_Background}" BorderBrush="Blue" BorderThickness="2" CornerRadius="5" Margin="2,5,5,2" HorizontalAlignment="Left" > <Grid> <Grid.ColumnDefinitions > <ColumnDefinition Width="Auto"/> <ColumnDefinition Width="*"/> <ColumnDefinition Width="*"/> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions> <TextBlock MinWidth="80" HorizontalAlignment="Left" Grid.Column="0" Margin="5,2,2,2" Grid.Row ="0" Text="{Binding Path=ColName}"/> <ComboBox Name="cboColType" Grid.Column="1" HorizontalAlignment="Right" ItemsSource="{Binding Source={StaticResource dataFromEnum}}" SelectedItem="{Binding Path=ColumnType}" Margin="2,2,2,2" local:ItemSelectedBehavior.ItemSelected="{Binding Path=LoadConfigCommand}" /> </Grid> </Border> </HierarchicalDataTemplate> I also tried creating a style <Style x:Key="childItemStyle" TargetType="{x:Type FrameworkElement}"> <Setter Property="local:ItemSelectedBehavior.ItemSelected" Value="{Binding Path=LoadConfigCommand}" /> </Style> and setting the itemcontainerstyle to the style in the hierarchical datatemplate..still no luck .. <HierarchicalDataTemplate> ... <ComboBox Name="cboColType" Grid.Column="1" HorizontalAlignment="Right" ItemsSource="{Binding Source={StaticResource dataFromEnum}}" SelectedItem="{Binding Path=ColumnType}" Margin="2,2,2,2" ItemContainerStyle={StaticeResource childItemStyle}" /> ... </HierarchicalDataTemplate> I'm still learning a lot about WPF so I'm assuming there is something particular about the hierchical datatemplate that is not allowing the attache dproperty to be set..I have found similar posts in the forums and tried to implement their solutions as above, but after a day of searching and experimenting wiht no luck I'm hoping some one has an idea about this...

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• Insertions into Zipper trees on XML files in Clojure

  - by ivar

  I'm confused as how to idiomatically change a xml tree accessed through clojure.contrib's zip-filter.xml. Should be trying to do this at all, or is there a better way? Say that I have some dummy xml file "itemdb.xml" like this: <itemlist> <item id="1"> <name>John</name> <desc>Works near here.</desc> </item> <item id="2"> <name>Sally</name> <desc>Owner of pet store.</desc> </item> </itemlist> And I have some code: (require '[clojure.zip :as zip] '[clojure.contrib.duck-streams :as ds] '[clojure.contrib.lazy-xml :as lxml] '[clojure.contrib.zip-filter.xml :as zf]) (def db (ref (zip/xml-zip (lxml/parse-trim (java.io.File. "itemdb.xml"))))) ;; Test that we can traverse and parse. (doall (map #(print (format "%10s: %s\n" (apply str (zf/xml-> % :name zf/text)) (apply str (zf/xml-> % :desc zf/text)))) (zf/xml-> @db :item))) ;; I assume something like this is needed to make the xml tags (defn create-item [name desc] {:tag :item :attrs {:id "3"} :contents (list {:tag :name :attrs {} :contents (list name)} {:tag :desc :attrs {} :contents (list desc)})}) (def fred-item (create-item "Fred" "Green-haired astrophysicist.")) ;; This disturbs the structure somehow (defn append-item [xmldb item] (zip/insert-right (-> xmldb zip/down zip/rightmost) item)) ;; I want to do something more like this (defn append-item2 [xmldb item] (zip/insert-right (zip/rightmost (zf/xml-> xmldb :item)) item)) (dosync (alter db append-item2 fred-item)) ;; Save this simple xml file with some added stuff. (ds/spit "appended-itemdb.xml" (with-out-str (lxml/emit (zip/root @db) :pad true))) I am unclear about how to use the clojure.zip functions appropriately in this case, and how that interacts with zip-filter. If you spot anything particularly weird in this small example, please point it out.

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• How can I position some divs inside an unordered list so they line up with the root element of the l

  - by Ronedog

  I want to position all the divs to line up to the left on the same x coordinate so it looks nice. Notice the picture below, how based on the number of nested categories the div (and its contents) show up at slightly different x coordinates. I need to have the div's line up at exactly the same x coordinate no matter how deeply nested. Note, the bottom most category always has a div for the content, but that div has to be situated inside the last < li . I am using an unordered list to display the menu and thought the best solution would be to grab the root category (Cat 2, and mCat1) and obtain their left offset using jquery, then simply use that value to update the positioning of the div...but I couldn't seem to get it to work just right. I would appreciate any advice or help that you are willing to give. Heres the HTML <ul id="nav> <li>Cat 2 <ul> <li>sub cat2</li> </ul> </li> <li>mCat1 <ul> <li>Subcat A <ul> <li>Subcat A.1 <ul> <li>Annie</li> </ul> </li> </ul> </li> </ul> </li> </ul> Heres some jquery I tried (I have do insert the div inside this .each() loop in order to retrieve some values, but basically, this selector is grabbing the last < li in the menu tree and placing a div after it and that is the div that I want to position. the 245 value was something I was playing around with to see how I could get things to line up, and I know its out of wack, but the problem is still the same no matter what I do: $("#nav li:not(:has(li))").each(function () { var self = $(this); var position = self.offset(); var xLeft = Math.round(position.left)- 245; console.log("xLeft:", xLeft ); self.after( '<div id="' + self.attr('p_node') + '_p_cont_div" class="property_position" style="display:none; left:' + xLeft + 'px;" /> ' ); }); Heres the css: .property_position{ float:left; position: relative; top: 0px; padding-top:5px; padding-bottom:10px; }

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• Rtti accessing fields and properties in complex data structures

  - by Coco

  As already discussed in Rtti data manipulation and consistency in Delphi 2010 a consistency between the original data and rtti values can be reached by accessing members by using a pair of TRttiField and an instance pointer. This would be very easy in case of a simple class with only basic member types (like e.g. integers or strings). But what if we have structured field types? Here is an example: TIntArray = array [0..1] of Integer; TPointArray = array [0..1] of Point; TExampleClass = class private FPoint : TPoint; FAnotherClass : TAnotherClass; FIntArray : TIntArray; FPointArray : TPointArray; public property Point : TPoint read FPoint write FPoint; //.... and so on end; For an easy access of Members I want to buil a tree of member-nodes, which provides an interface for getting and setting values, getting attributes, serializing/deserializing values and so on. TMemberNode = class private FMember : TRttiMember; FParent : TMemberNode; FInstance : Pointer; public property Value : TValue read GetValue write SetValue; //uses FInstance end; So the most important thing is getting/setting the values, which is done - as stated before - by using the GetValue and SetValue functions of TRttiField. So what is the Instance for FPoint members? Let's say Parent is the Node for TExample class, where the instance is known and the member is a field, then Instance would be: FInstance := Pointer (Integer (Parent.Instance) + TRttiField (FMember).Offset); But what if I want to know the Instance for a record property? There is no offset in this case. So is there a better solution to get a pointer to the data? For the FAnotherClass member, the Instance would be: FInstance := Parent.Value.AsObject; So far the solution works, and data manipulation can be done by using rtti or the original types, without losing information. But things get harder, when working with arrays. Especially the second array of Points. How can I get the instance for the members of points in this case?

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• Why don't my scrollbars work properly when programmatically hiding rows in silverlight Datagrid?

  - by Luke Vilnis

  I have a Silverlight datagrid with custom code that allows for +/- buttons on the lefthand side and can display a table with a tree structure. The +/- buttons are bound to a IsExpanded property on my ViewModelRows, as I call them. The visibility of rows is bound to an IsVisible property on the ViewModelRows which is determined based on whether or not all of the parent rows are expanded. Straightforward enough. This code works fine in that if I scroll up and down the grid with PageUp/PageDown or the arrow keys, all the right rows are hidden and everything has the right structure and I can play with the +/- buttons to my hearts content. However, the vertical scroll bar on the right hand side, although it starts off the correct size and it scrolls through the rows smoothly, when I collapse rows and then re-expand them, doesn't go back to its correct size. The scrollbar can still usually be moved around to scroll through the whole collection, but because it is too big, once the bar moves to the bottom, there are still more rows to go through and it sort of jerkily shoots all the way down to the bottom or sometimes fails to scroll at all. This is pretty hard to describe so I included a screenshot with the black lines drawn on to show the difference in scrollbar length even though the two grids have the same number of rows expanded. I think this might be a bug related to the way the Datagrid does virtualization of rows. It seems to me like it isn't properly keeping track of how tall each row is supposed to be when expansion states change. Is there a way to programmatically "poke" (read hack) it to recalculate its scrollbar size on LoadingRow or something ugly like that? I'd include a code sample but there's 2 c# files and 1 xaml file so I wanted to see if anyone else has heard of this sort of issue before I try to make it reproducible in a self-contained way. Once again, scrolling with the arrow keys works fine so I'm pretty sure the underlying logic and binding is working, there's just some issue with the row height not being calculated properly. Since I'm a new user, it won't let me use image tags so here's the link to a picture of the problem: http://img210.imageshack.us/img210/8760/messedupscrollbars.png

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• Auto showing tips and closing popup when lost focus

  - by darkwindkey

  I have two elements: a TextBox, and a Popup, where the popup contains a tree view to show some tips according to text of TextBox. When the textBox got the KeyDown Event, the KeyDown directly executes pup.IsOpen=true to show the popup tips. However, I also want to show the popup tips when the mouse on clicking the TextBox, and auto closing the popups when the mouse click on any place (besides the TextBox and the TreeView in Popup). I have tried some cases but do not works fine. Case1: Add pup.IsOpen=true; in TextBox.PreviewMouseUp, the popup will stay opening, even if I click any other place in the window. Case2: Add pup.IsOpen=true in TextBox.PreviewMouseDown, the popup tips only shows on keep clicking the Mouse. Case3: Using CheckBox with Binding IsChecked to Popup.IsOpen works fine. but the tips is listed according to the content of the TextBox, therefore the checkbox is not editable for user... Here is my code now: <Window x:Class="popUpTesting.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Grid> <TextBox Name="SearchBox" HorizontalAlignment="Center" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Center" KeyDown="SearchBox_KeyDown" PreviewMouseUp="SearchBox_PreviewMouseUp" /> <Popup Placement="Bottom" AllowsTransparency="True" PopupAnimation="Fade" StaysOpen="false" x:Name="pup" PlacementTarget="{Binding ElementName=SearchBox}" IsOpen="False" > <Grid> <TreeView HorizontalAlignment="Left" Height="200" VerticalAlignment="Top" Width="200"> <TreeViewItem Header="A"> <TreeViewItem Header="A1"/> </TreeViewItem> <TreeViewItem Header="B"></TreeViewItem> <TreeViewItem Header="C"></TreeViewItem> <TreeViewItem Header="D"></TreeViewItem> </TreeView> </Grid> </Popup> </Grid> </Window> and the event functions: private void SearchBox_KeyDown(object sender, KeyEventArgs e) { pup.IsOpen = true; } private void SearchBox_PreviewMouseUp(object sender, MouseButtonEventArgs e) { pup.IsOpen = true; }

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• Is this scatter-brained workflow realizable in Git?

  - by Luke Maurer

  This is what I'd like my workflow to look like at a conceptual level: I hack on my new feature for a while I notice a typo in a comment I change it Since the typo is completely unrelated to anything else, I put that change in a pile of comment fixes I keep working on the code I realize I need to flesh out a few utility functions I do so I put that change in its own pile Steps 2, 3, and 4 each repeat throughout the day I finish the new feature and put the changes for that feature in a pile I push nice patches upstream: One with the new feature, a few for the other tweaks, and one with a bunch of comment fixes if enough have accumulated Since I'm both lazy and a perfectionist, I want to be able to do some things out of order: I might correct a typo but forget to put it in the comment fix pile; when I prepare the upstream patches (I'm using git-svn, so I need to be pretty deliberate about these), I'll then pull out the comment fixes at that point. I might forget to separate things altogether until the very end. But I might /also/ have committed some of the piles along the way (sorry, the metaphor is breaking down …). This is all rather like just using Eclipse changesets with SVN, only I can have different changes to the same file in different piles (having to disentangle changes into different commits is what motivated me to move to git-svn, in fact …), and with Git I can have my full discombobulated change history, experimental branches and all, but still make a nice, neat patch. I've just recently started with Git after having wanted to for a good while, and I'm quite happy so far. The biggest way in which the above workflow doesn't really map into Git, though, is that a “bin” can't really be just a local branch, since the working tree only ever reflects the state of a single branch. Or maybe the Git index is a “pile,” and what I want is to have more than one somehow (effectively). I can think of a few ways to approximate what I want (maybe creative use of stash? Intricate stash-checkout-merge dances?), but my grasp on Git isn't solid enough to be sure of how best to put all the pieces together. It's said that Git is more a toolkit than a VCS, so I guess the question comes down to: How do I build this thing with these tools?

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• How to group items by date range in XSLT?

  - by glenatron

  I have a bunch of data that looks a little like this: <item> <colour>Red</colour> <date_created>2009-10-10 12:01:55</date_created> <date_sold>2009-10-20 22:32:12</date_sold> </item> <item> <colour>Blue</colour> <date_created>2009-11-01 13:21:00</date_created> <date_sold>2009-11-21 12:32:12</date_sold> </item> <item> <colour>Blue</colour> <date_created>2009-10-29 21:23:02</date_created> <date_sold>2009-10-20 02:02:22</date_sold> </item> <item> <colour>Red</colour> <date_created>2009-11-02 09:11:51</date_created> <date_sold>2009-11-20 09:15:53</date_sold> </item> <item> <colour>Red</colour> <date_created>2009-10-18 11:00:55</date_created> <date_sold>2009-10-20 11:12:22</date_sold> </item> Now what I would like to be able to do is to run that through an XSLT stylesheet such that I get ouput looking like this: Colour | In stock 1 week | In stock 2 weeks | In stock 3 weeks Red | 1 | 3 | 2 Blue | 0 | 2 | 1 Currently I have a stylesheet that uses basic muenchian grouping to show that 30% of stock was Red and 70% blue, but I can't see a way to find the number of nodes withing a given date range. Is there a way to use keys to select a range? Do I need to create some kind of intermediate data node? Is there a different route that shows I'm barking up the wrong tree with both those suggestions? Is this even possible with XSLT or do I need to find a way to change the data source?

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• How do i pass arraycollection to Advancedatagrid using HierarchicalData ?

  - by R.Vijayakumar

  Problem with passing arraycollection to Advance datagrid. My Arraycollection structure like `   private var groupList:ArrayCollection = new ArrayCollection([ {Country:'India', children:[ {Country:'Series1', children:[                                {Matches:'India Test series 1',isEnable:false,id:1,isSelected:true},                                {Matches:'India Test series 2',isEnable:false,id:2,isSelected:true},                                {Matches:'India Test series 3',isEnable:false,id:3,isSelected:true}]},              {Country:'Series2', children:[                                {Matches:'Australia Test series 1',isEnable:false,id:25,isSelected:true},                                {Matches:'Australia Test series 2',isEnable:false,id:26,isSelected:true},                                {Matches:'Australia Test series 3',isEnable:false,id:27,isSelected:true}]} ]}, {Country:'Austrila', children:[ {Country:'Series1', children:[                                {Matches:'Australia Test series 1',isEnable:false,id:46,isSelected:true},                                {Matches:'Australia Test series 2',isEnable:false,id:47,isSelected:true},                                {Matches:'Australia Test series 3',isEnable:false,id:48,isSelected:true}]}, {Country:'Series2', children:[                                {Matches:'Australia Test series 1',isEnable:false,id:49,isSelected:true},                                {Matches:'Australia Test series 2',isEnable:false,id:50,isSelected:true},                                {Matches:'Australia Test series 3',isEnable:false,id:51,isSelected:true}]}, {Country:'Series3', children:[                                {Matches:'Australia Test series 1',isEnable:false,id:52,isSelected:true},                                {Matches:'Australia Test series 2',isEnable:false,id:53,isSelected:true},                                {Matches:'Australia Test series 3',isEnable:false,id:54,isSelected:true}]} ]} passing AD in dataProvider="{new HierarchicalData(groupList)}" It's working fine. it's show two menu of tree and childrens based on country .But i tried dynamic xml convert to Arraycollection by below code private function convertXmlToArrayCollection( file:String ):ArrayCollection { var xml:XMLDocument = new XMLDocument( file ); //var decoder:SimpleXMLDecoder = new SimpleXMLDecoder(); var decoder1:SimpleXMLDecoder = new SimpleXMLDecoder(true); var data1:Object = decoder1.decodeXML( xml ); var array1:Array = ArrayUtil.toArray(data1); return new ArrayCollection( array1 ); } my xml structure is <Country Country="India "> <Country Country="Series "> <Matches Matches="BIndependiente-Colon" id="701536" isEnable="false" isSelected="true" startDate="2009-10-29 01:30:00" EndDate="2009-10-29 01:30:00"/> <Matches Matches="Boca Juniors-Chacarita Juniors" id="701633" isEnable="false" isSelected="true" startDate="2009-10-29 19:00:00" EndDate=""/> </Country> </Country> <Country Country="Australia"> <Country Country="series"> <Matches Matches="BIndependiente-Colon" id="701536" isEnable="false" isSelected="true" startDate="2009-10-29 01:30:00" EndDate="2009-10-29 01:30:00"/> <Matches Matches="Boca Juniors-Chacarita Juniors" id="701633" isEnable="false" isSelected="true" startDate="2009-10-29 19:00:00" EndDate=""/> </Country> </Country> So if i tried to convert this format of xml code to arryacollection , it converted the array collection but when will i pass to Advance data grid it not show any result . What did i wrong ? groupList1= convertXmlToArrayCollection(string1); Alert.show(groupList1[0].Country[0].Matches[0].id.toString());// output is =701536 Where did i mistake it ? Plz kindly any one refer me , What will i changed ?

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• Parsing line and selecting values corresponding to a key

  - by gagneet

  there is a set of data which is arranged in a specific manner (as a tree), as is given below. basically a key=value pair, with some additional values at the end, which informs how many children does the branch have and some junk value. 11=1 123 2 11=1>1=45 234 1 11=1>1=45>9=16 345 1 11=1>1=45>9=16>2=34 222 1 11=1>1=45>9=16>2=34>7=0 2234 1 11=1>1=45>9=16>2=34>7=0>8=0 22345 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138 22234 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0 5566 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0>4=0 664 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0>4=0>6=10 443 1 11=1>1=45>9=16>2=34>7=0>8=0>0=138>5=0>4=0>6=10>3=11 445 0 11=1>1=47 4453 1 11=1>1=47>9=16 887 1 11=1>1=47>9=16>2=34 67 1 11=1>1=47>9=16>2=340>7=0 98 1 11=1>1=47>9=16>2=34>7=0>8=0 654 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138 5789 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138>5=0 9870 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138>5=0>4=0 3216 1 11=1>1=47>9=16>2=34>7=0>8=0>0=138>5=0>4=0>6=10>3=11 66678 0 my problem is to get the appropriate branch from the above data, which satisfies exactly the values, which i give as the input. suppose, my input value to search in the above data stack are: 5=0 4=0 6=10 3=11 11=1 1=45 0=138 9=16 2=34 7=0 8=0 for the above given list of key-values, the function should return 11=11=459=162=347=08=00=1385=04=06=103=11 as the match. likewise, for another input file, in which another set of keys is given: 5=0 4=0 6=10 3=11 11=1 1=45 9=16 2=34 7=0 8=0 the function should return 11=11=459=162=347=08=0 1 as the match. not the last line; as that would also match all the values given in my input key, but, i want only the exact match. Also, I want to find out how many nodes were selected in the given array. (separated by ). What will be the best way to implement this kind of scenario?

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• XML validation in Java - why does this fail?

  - by jd

  hi, first time dealing with xml, so please be patient. the code below is probably evil in a million ways (I'd be very happy to hear about all of them), but the main problem is of course that it doesn't work :-) public class Test { private static final String JSDL_SCHEMA_URL = "http://schemas.ggf.org/jsdl/2005/11/jsdl"; private static final String JSDL_POSIX_APPLICATION_SCHEMA_URL = "http://schemas.ggf.org/jsdl/2005/11/jsdl-posix"; public static void main(String[] args) { System.out.println(Test.createJSDLDescription("/bin/echo", "hello world")); } private static String createJSDLDescription(String execName, String args) { Document jsdlJobDefinitionDocument = getJSDLJobDefinitionDocument(); String xmlString = null; // create the elements Element jobDescription = jsdlJobDefinitionDocument.createElement("JobDescription"); Element application = jsdlJobDefinitionDocument.createElement("Application"); Element posixApplication = jsdlJobDefinitionDocument.createElementNS(JSDL_POSIX_APPLICATION_SCHEMA_URL, "POSIXApplication"); Element executable = jsdlJobDefinitionDocument.createElement("Executable"); executable.setTextContent(execName); Element argument = jsdlJobDefinitionDocument.createElement("Argument"); argument.setTextContent(args); //join them into a tree posixApplication.appendChild(executable); posixApplication.appendChild(argument); application.appendChild(posixApplication); jobDescription.appendChild(application); jsdlJobDefinitionDocument.getDocumentElement().appendChild(jobDescription); DOMSource source = new DOMSource(jsdlJobDefinitionDocument); validateXML(source); try { Transformer transformer = TransformerFactory.newInstance().newTransformer(); transformer.setOutputProperty(OutputKeys.INDENT, "yes"); StreamResult result = new StreamResult(new StringWriter()); transformer.transform(source, result); xmlString = result.getWriter().toString(); } catch (Exception e) { e.printStackTrace(); } return xmlString; } private static Document getJSDLJobDefinitionDocument() { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = null; try { builder = factory.newDocumentBuilder(); } catch (Exception e) { e.printStackTrace(); } DOMImplementation domImpl = builder.getDOMImplementation(); Document theDocument = domImpl.createDocument(JSDL_SCHEMA_URL, "JobDefinition", null); return theDocument; } private static void validateXML(DOMSource source) { try { URL schemaFile = new URL(JSDL_SCHEMA_URL); Sche maFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI); Schema schema = schemaFactory.newSchema(schemaFile); Validator validator = schema.newValidator(); DOMResult result = new DOMResult(); validator.validate(source, result); System.out.println("is valid"); } catch (Exception e) { e.printStackTrace(); } } } it spits out a somewhat odd message: org.xml.sax.SAXParseException: cvc-complex-type.2.4.a: Invalid content was found starting with element 'JobDescription'. One of '{"http://schemas.ggf.org/jsdl/2005/11/jsdl":JobDescription}' is expected. Where am I going wrong here? Thanks a lot

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• Rest API Web Service - iOS

  - by zeekerg

  Its my first time to use web service in iOS. REST was my first choice and I use code igniter to form it. I have my Controller: require APPPATH.'/libraries/REST_Controller.php'; class Sample extends REST_Controller { function example_get() { $this->load->helper('arh'); $this->load->model('users'); $users_array = array(); $users = $this->users->get_all_users(); foreach($users as $user){ $new_array = array( 'id'=>$user->id , 'name'=>$user->name, 'age'=>$user->age, ); array_push( $users_array, $new_array); } $data['users'] = $users_array; if($data) { $this->response($data, 200); } } function user_put() { $this->load->model('users'); $this->users->insertAUser(); $message = array('message' => 'ADDED!'); $this->response($message, 200); } } , using my web browser, accessing the URL http://localhost:8888/restApi/index.php/sample/example/format/json really works fine and gives this output: {"users":[{"id":"1","name":"Porcopio","age":"99"},{"id":"2","name":"Name1","age":"24"},{"id":"3","name":"Porcopio","age":"99"},{"id":"4","name":"Porcopio","age":"99"},{"id":"5","name":"Luna","age":"99"}]} , this gives me a great output using RKRequest by RestKit in my app. The problem goes with the put method. This URL : http://localhost:8888/restApi/index.php/sample/user always give me an error like this: This XML file does not appear to have any style information associated with it. The document tree is shown below. <xml> <status/> <error>Unknown method.</error> This is my Users model <?php class Users extends CI_Model { function __construct() { parent::__construct(); } function get_all_users() { $this->load->database(); $query = $this->db->get('users'); return $query->result(); } function insertAUser(){ $this->load->database(); $data = array('name'=> "Sample Name", 'age'=>"99"); $this->db->insert('users', $data); } } ?> What is the work around for my _put method why am I not inserting anything? Thanks all!

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• c++ quick sort running time

  - by chnet

  I have a question about quick sort algorithm. I implement quick sort algorithm and play it. The elements in initial unsorted array are random numbers chosen from certain range. I find the range of random number effects the running time. For example, the running time for 1, 000, 000 random number chosen from the range (1 - 2000) takes 40 seconds. While it takes 9 seconds if the 1,000,000 number chosen from the range (1 - 10,000). But I do not know how to explain it. In class, we talk about the pivot value can effect the depth of recursion tree. For my implementation, the last value of the array is chosen as pivot value. I do not use randomized scheme to select pivot value. int partition( vector<int> &vec, int p, int r) { int x = vec[r]; int i = (p-1); int j = p; while(1) { if (vec[j] <= x){ i = (i+1); int temp = vec[j]; vec[j] = vec[i]; vec[i] = temp; } j=j+1; if (j==r) break; } int temp = vec[i+1]; vec[i+1] = vec[r]; vec[r] = temp; return i+1; } void quicksort ( vector<int> &vec, int p, int r) { if (p<r){ int q = partition(vec, p, r); quicksort(vec, p, q-1); quicksort(vec, q+1, r); } } void random_generator(int num, int * array) { srand((unsigned)time(0)); int random_integer; for(int index=0; index< num; index++){ random_integer = (rand()%10000)+1; *(array+index) = random_integer; } } int main() { int array_size = 1000000; int input_array[array_size]; random_generator(array_size, input_array); vector<int> vec(input_array, input_array+array_size); clock_t t1, t2; t1 = clock(); quicksort(vec, 0, (array_size - 1)); // call quick sort int length = vec.size(); t2 = clock(); float diff = ((float)t2 - (float)t1); cout << diff << endl; cout << diff/CLOCKS_PER_SEC <<endl; }

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• Can my loop be optimized any more? (C++)

  - by Sagekilla

  Below is one of my inner loops that's run several thousand times, with input sizes of 20 - 1000 or more. Is there anything I can do to help squeeze any more performance out of this? I'm not looking to move this code to something like using tree codes (Barnes-Hut), but towards optimizing the actual calculations happening inside, since the same calculations occur in the Barnes-Hut algorithm. Any help is appreciated! typedef double real; struct Particle { Vector pos, vel, acc, jerk; Vector oldPos, oldVel, oldAcc, oldJerk; real mass; }; class Vector { private: real vec[3]; public: // Operators defined here }; real Gravity::interact(Particle *p, size_t numParticles) { PROFILE_FUNC(); real tau_q = 1e300; for (size_t i = 0; i < numParticles; i++) { p[i].jerk = 0; p[i].acc = 0; } for (size_t i = 0; i < numParticles; i++) { for (size_t j = i+1; j < numParticles; j++) { Vector r = p[j].pos - p[i].pos; Vector v = p[j].vel - p[i].vel; real r2 = lengthsq(r); real v2 = lengthsq(v); // Calculate inverse of |r|^3 real r3i = Constants::G * pow(r2, -1.5); // da = r / |r|^3 // dj = (v / |r|^3 - 3 * (r . v) * r / |r|^5 Vector da = r * r3i; Vector dj = (v - r * (3 * dot(r, v) / r2)) * r3i; // Calculate new acceleration and jerk p[i].acc += da * p[j].mass; p[i].jerk += dj * p[j].mass; p[j].acc -= da * p[i].mass; p[j].jerk -= dj * p[i].mass; // Collision estimation // Metric 1) tau = |r|^2 / |a(j) - a(i)| // Metric 2) tau = |r|^4 / |v|^4 real mij = p[i].mass + p[j].mass; real tau_est_q1 = r2 / (lengthsq(da) * mij * mij); real tau_est_q2 = (r2*r2) / (v2*v2); if (tau_est_q1 < tau_q) tau_q = tau_est_q1; if (tau_est_q2 < tau_q) tau_q = tau_est_q2; } } return sqrt(sqrt(tau_q)); }

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• String manipulation in Linux kernel module

  - by user577066

  I am having a hard time in manipulating strings while writing module for linux. My problem is that I have a int Array[10] with different values in it. I need to produce a string to be able send to the buffer in my_read procedure. If my array is {0,1,112,20,4,0,0,0,0,0} then my output should be: 0:(0) 1:-(1) 2:-------------------------------------------------------------------------------------------------------(112) 3:--------------------(20) 4:----(4) 5:(0) 6:(0) 7:(0) 8:(0) 9:(0) when I try to place the above strings in char[] arrays some how weird characters end up there here is the code int my_read (char *page, char **start, off_t off, int count, int *eof, void *data) { int len; if (off > 0){ *eof =1; return 0; } /* get process tree */ int task_dep=0; /* depth of a task from INIT*/ get_task_tree(&init_task,task_dep); char tmp[1024]; char A[ProcPerDepth[0]],B[ProcPerDepth[1]],C[ProcPerDepth[2]],D[ProcPerDepth[3]],E[ProcPerDepth[4]],F[ProcPerDepth[5]],G[ProcPerDepth[6]],H[ProcPerDepth[7]],I[ProcPerDepth[8]],J[ProcPerDepth[9]]; int i=0; for (i=0;i<1024;i++){ tmp[i]='\0';} memset(A, '\0', sizeof(A));memset(B, '\0', sizeof(B));memset(C, '\0', sizeof(C)); memset(D, '\0', sizeof(D));memset(E, '\0', sizeof(E));memset(F, '\0', sizeof(F)); memset(G, '\0', sizeof(G));memset(H, '\0', sizeof(H));memset(I, '\0', sizeof(I));memset(J, '\0', sizeof(J)); printk("A:%s\nB:%s\nC:%s\nD:%s\nE:%s\nF:%s\nG:%s\nH:%s\nI:%s\nJ:%s\n",A,B,C,D,E,F,G,H,I,J); memset(A,'-',sizeof(A)); memset(B,'-',sizeof(B)); memset(C,'-',sizeof(C)); memset(D,'-',sizeof(D)); memset(E,'-',sizeof(E)); memset(F,'-',sizeof(F)); memset(G,'-',sizeof(G)); memset(H,'-',sizeof(H)); memset(I,'-',sizeof(I)); memset(J,'-',sizeof(J)); printk("A:%s\nB:%s\nC:%s\nD:%s\nE:%s\nF:%s\nG:%s\nH:%s\nI:%s\nJ:%\n",A,B,C,D,E,F,G,H,I,J); len = sprintf(page,"0:%s(%d)\n1:%s(%d)\n2:%s(%d)\n3:%s(%d)\n4:%s(%d)\n5:%s(%d)\n6:%s(%d)\n7:%s(%d)\n8:%s(%d)\n9:%s(%d)\n",A,ProcPerDepth[0],B,ProcPerDepth[1],C,ProcPerDepth[2],D,ProcPerDepth[3],E,ProcPerDepth[4],F,ProcPerDepth[5],G,ProcPerDepth[6],H,ProcPerDepth[7],I,ProcPerDepth[8],J,ProcPerDepth[9]); return len; }

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• Want to set 'src' of script to my IP-Won't load in Safari or Chrome. Relative link asp.netmvc

  - by Ozaki

  I have a script that links to the server I am hosting (IP can change) usually I would just use for links: var url ='http://' + window.location.hostname + 'end of url'; But in this case it isnt appearing to be so easy. I have tried: (1) $('#scriptid').attr('src', url); as well as: (2) var script = document.createElement( 'script' ); script.type = 'text/javascript'; script.src = url; $("#insert").append( script ); Now case (2) works loads the script runs the script. But when at the end of my script it hits the 'write data' it decides to replace the entire page with just the data. Any idea on how I can do this? Note: I am using plain html not ASP. With ASP backend that is just the way it has to be. Ok it now is <script src="myscript.js"></script> C# router.AddAsyncRoute("myscript.js"...... It workes in IE & FF. But I get blank pages in Chrome & Safari. I am using document.write to write a script onto my page. Any ideas why Chrome & Safari don't like this? I am so far assuming that in Crhome & Safari it takes longer to run the script therefore launching the document.write after the DOM has loaded therefore replacing the page with a blank one. edit the script im trying to run is a modification of: d = new dTree('d'); d.add(0,-1,'My example tree'); d.add(1,0,'Node 1','default.html'); d.add(2,0,'Node 2','default.html'); d.add(3,1,'Node 1.1','default.html'); d.add(4,0,'Node 3','default.html'); d.add(5,3,'Node 1.1.1','default.html') document.write(d); Any ideas how I can get around this? I am not to sure how to implement an appenChild in this case as the script is changing constantly with live data. So every refresh it will generally have changed some...

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• Is there any alternative to obfuscation to make it harder to get any string in javascript?

  - by MarceloRamires

  I use DropBox and I've had some trouble reaching to my files from other computers: I not always want to login to anything when I'm in a public computer, but I like being able to reach my stuff from wherever I am. So I've made a simple little application that when put in the public folder, ran and given the right UID, creates (still in your public folder) an HTML of all the content in the folder (including subfolders) as a tree of links. But I didn't risk loading it anywhere, since there are slightly private things in there (yes, I know that the folder's name is "PUBLIC"). So I've came up with the idea to make it a simple login page, given the right password, the rest of the page should load. brilliant!, but how? If I did this by redirecting to other HTML on the same folder, I'd still put the html link in the web history and the "url's accessed" history of the administrator. So I should generate itin the same page. I've done it. And currently the page is a textbox and a button, and only if you type in the right password (asked by the generator) the rest of the page loads. The fault is that everything (password, URL's) is easily reachable through the sourcecode. Now, assuming I only want to avoid silly people to get it all too easily, not make a bulletproof all-content-holding NSA certified website, I though about some ways to make these informations a bit harder to get. As you may have already figured, I use a streamwritter to write a .HTM file (head, loop through links, bottom), then it's extremely configurable, and I can come up with a pretty messy-but-working c# code, though my javascript knowledge is not that good. Public links in DropBox look like this: http://dl.dropbox.com/u/3045472/img.png Summarizing: How do I hide stuff (MAINLY the password, of course) in my source-code so that no bumb-a-joe that can read, use a computer and press CTRL+U can reach to my stuff too easily ? PS.: It's not that personal, if someone REALLY wants it, it could never be 100% protected, and if it was that important, I wouldnt put it in the public folder, also, if the dude really wants to get it that hard, he should deserve it. PS2.: "Use the ultra-3000'tron obfuscator!!11" is not a real answer, since my javascript is GENERATED by my c# program. PS3.: I don't want other solutions as "use a serverside application and host it somewhere to redirect and bla bla" or "compress the links in a .RAR file and put a password in it" since I'm doing this ALSO to learn, and I want the thrill of it =)

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• QTreeView memory consumption

  - by Eye of Hell

  Hello. I'm testing QTreeView functionality right now, and i was amazed by one thing. It seems that QTreeView memory consumption depends on items count O_O. This is highly unusual, since model-view containers of such type only keeps track for items being displayed, and rest of items are in the model. I have written a following code with a simple model that holds no data and just reports that it has 10 millions items. With MFC, Windows API or .NET tree / list with such model will take no memory, since it will display only 10-20 visible elements and will request model for more upon scrolling / expanding items. But with Qt, such simple model results in ~300Mb memory consumtion. Increasing number of items will increase memory consumption. Maybe anyone can hint me what i'm doing wrong? :) #include <QtGui/QApplication> #include <QTreeView> #include <QAbstractItemModel> class CModel : public QAbstractItemModel { public: QModelIndex index ( int i_nRow, int i_nCol, const QModelIndex& i_oParent = QModelIndex() ) const { return createIndex( i_nRow, i_nCol, 0 ); } public: QModelIndex parent ( const QModelIndex& i_oInex ) const { return QModelIndex(); } public: int rowCount ( const QModelIndex& i_oParent = QModelIndex() ) const { return i_oParent.isValid() ? 0 : 1000 * 1000 * 10; } public: int columnCount ( const QModelIndex& i_oParent = QModelIndex() ) const { return 1; } public: QVariant data ( const QModelIndex& i_oIndex, int i_nRole = Qt::DisplayRole ) const { return Qt::DisplayRole == i_nRole ? QVariant( "1" ) : QVariant(); } }; int main(int argc, char *argv[]) { QApplication a(argc, argv); QTreeView oWnd; CModel oModel; oWnd.setUniformRowHeights( true ); oWnd.setModel( & oModel ); oWnd.show(); return a.exec(); }

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• Copy all childNodes to an other element. In javascript native way.

  - by kroko

  Hello I have to change "unknown" contents of XML. The structure and content itself is valid. Original <blabla foo="bar"> <aa>asas</aa> <ff> <cc> <dd /> </cc> </ff> <gg attr2="2"> </gg> ... ... </blabla> becomes <blabla foo="bar"> <magic> <aa>asas</aa> <ff> <cc> <dd /> </cc> </ff> <gg attr2="2"> </gg> ... ... </magic> </blabla> thus, adding a child straight under document root node (document.documentElement) and "pushing" the "original" children under that. Here it has to be done in plain javascript (ecmascript). The idea now is to // Get the root node RootNode = mymagicdoc.documentElement; // Create new magic element (that will contain contents of original root node) var magicContainer = mymagicdoc.createElement("magic"); // Copy all root node children (and their sub tree - deep copy) to magic node /* ????? here RootNodeClone = RootNode.cloneNode(true); RootNodeClone.childNodes...... */ // Remove all children from root node while(RootNode.hasChildNodes()) RootNode.removeChild(RootNode.firstChild); // Now when root node is empty add the magicContainer // node in it that contains all the children of original root node RootNode.appendChild(magicContainer); How to do that /* */ step? Or maybe someone has a much better solution in general for achieving the desirable result? Thank you in advance!

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• how to filter data from xml file for displaying only selected as nodes in treeview

  - by michale

  I have an xml file named "books.xml" provided in the link "http://msdn.microsoft.com/en-us/library/windows/desktop/ms762271(v=vs.85).aspx". What my requirement was to disaplay only the <title> from xml information as nodes in tree view. But when i did the following coding its displaying all the values as nodes like "catalog" as rootnode, book as parent node for all then author,title,genre etc as nodes but i want only root node catalogue and title as nodes not even book. Can any body guide me what modification i need to do in the exisitng logic for displaying title as nodes OpenFileDialog dlg = new OpenFileDialog(); dlg.Title = "Open XML document"; dlg.Filter = "XML Files (*.xml)|*.xml"; dlg.FileName = Application.StartupPath + "\\..\\..\\Sample.xml"; if (dlg.ShowDialog() == DialogResult.OK) { try { //Just a good practice -- change the cursor to a //wait cursor while the nodes populate this.Cursor = Cursors.WaitCursor; //First, we'll load the Xml document XmlDocument xDoc = new XmlDocument(); xDoc.Load(dlg.FileName); //Now, clear out the treeview, //and add the first (root) node treeView1.Nodes.Clear(); treeView1.Nodes.Add(new TreeNode(xDoc.DocumentElement.Name)); TreeNode tNode = new TreeNode(); tNode = (TreeNode)treeView1.Nodes[0]; //We make a call to addTreeNode, //where we'll add all of our nodes addTreeNode(xDoc.DocumentElement, tNode); //Expand the treeview to show all nodes treeView1.ExpandAll(); } catch (XmlException xExc) //Exception is thrown is there is an error in the Xml { MessageBox.Show(xExc.Message); } catch (Exception ex) //General exception { MessageBox.Show(ex.Message); } finally { this.Cursor = Cursors.Default; //Change the cursor back } }} //This function is called recursively until all nodes are loaded private void addTreeNode(XmlNode xmlNode, TreeNode treeNode) { XmlNode xNode; TreeNode tNode; XmlNodeList xNodeList; if (xmlNode.HasChildNodes) //The current node has children { xNodeList = xmlNode.ChildNodes; for (int x = 0; x <= xNodeList.Count - 1; x++) //Loop through the child nodes { xNode = xmlNode.ChildNodes[x]; treeNode.Nodes.Add(new TreeNode(xNode.Name)); tNode = treeNode.Nodes[x]; addTreeNode(xNode, tNode); } } else //No children, so add the outer xml (trimming off whitespace) treeNode.Text = xmlNode.OuterXml.Trim(); }

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• What are the Options for Storing Hierarchical Data in a Relational Database?

  - by orangepips

  Good Overviews One more Nested Intervals vs. Adjacency List comparison: the best comparison of Adjacency List, Materialized Path, Nested Set and Nested Interval I've found. Models for hierarchical data: slides with good explanations of tradeoffs and example usage Representing hierarchies in MySQL: very good overview of Nested Set in particular Hierarchical data in RDBMSs: most comprehensive and well organized set of links I've seen, but not much in the way on explanation Options Ones I am aware of and general features: Adjacency List: Columns: ID, ParentID Easy to implement. Cheap node moves, inserts, and deletes. Expensive to find level (can store as a computed column), ancestry & descendants (Bridge Hierarchy combined with level column can solve), path (Lineage Column can solve). Use Common Table Expressions in those databases that support them to traverse. Nested Set (a.k.a Modified Preorder Tree Traversal) First described by Joe Celko - covered in depth in his book Trees and Hierarchies in SQL for Smarties Columns: Left, Right Cheap level, ancestry, descendants Compared to Adjacency List, moves, inserts, deletes more expensive. Requires a specific sort order (e.g. created). So sorting all descendants in a different order requires additional work. Nested Intervals Combination of Nested Sets and Materialized Path where left/right columns are floating point decimals instead of integers and encode the path information. Bridge Table (a.k.a. Closure Table: some good ideas about how to use triggers for maintaining this approach) Columns: ancestor, descendant Stands apart from table it describes. Can include some nodes in more than one hierarchy. Cheap ancestry and descendants (albeit not in what order) For complete knowledge of a hierarchy needs to be combined with another option. Flat Table A modification of the Adjacency List that adds a Level and Rank (e.g. ordering) column to each record. Expensive move and delete Cheap ancestry and descendants Good Use: threaded discussion - forums / blog comments Lineage Column (a.k.a. Materialized Path, Path Enumeration) Column: lineage (e.g. /parent/child/grandchild/etc...) Limit to how deep the hierarchy can be. Descendants cheap (e.g. LEFT(lineage, #) = '/enumerated/path') Ancestry tricky (database specific queries) Database Specific Notes MySQL Use session variables for Adjacency List Oracle Use CONNECT BY to traverse Adjacency Lists PostgreSQL ltree datatype for Materialized Path SQL Server General summary 2008 offers HierarchyId data type appears to help with Lineage Column approach and expand the depth that can be represented.

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