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  • GAE Datastore: persisting referenced objects

    - by David
    Two "I'm sorries" to begin with: 1) I've looked for a solution (here, and elsewhere), and couldn't find the answer. 2) English is not my mother tongue, so I may have some typos and the sort - please ignore them. To the point: I am trying to persist Java objects to the GAE datastore. I am not sure as to how to persist object having ("non-trivial") referenced object. That is, assume I have the following. public class Father { String name; int age; Vector<Child> offsprings; //this is what I call "non-trivial" reference //ctor, getters, setters... } public class Child { String name; int age; Father father; //this is what I call "non-trivial" reference //ctor, getters, setters... } The name field is unique in each type domain, and is considered a Primary-Key. In order to persist the "trivial" (String, int) fields, all I need is to add the correct annotation. So far so good. However, I don't understand how should I persist the home-brewed (Child, Father) types referenced. Should I: Convert each such reference to hold the Primary-Key (a name String, in this example) instead of the "actual" object. So, Vector<Child> offsprings; becomes Vector<String> offspringsNames; ? If that is the case, how do I handle the object at run-time? Do I just query for the Primary-Key from Class.getName, to retrieve the refrenced objects? Convert each such reference to hold the actual Key provided to me by the Datastore upon the proper put() operation? So, Vector<Child> offsprings; becomes Vector<Key> offspringsHashKeys; ? I would very much appreciate all kinds of comments. I have read ALL the offical relevant GAE docs/example. Throughout, they always persist "trivial" references, natively supported by the Datastore (e.g. in the Guestbook example, only Strings, and Longs). Many thanks, David

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  • JSF: how to update the list after delete an item of that list

    - by Harry Pham
    It will take a moment for me to explain this, so please stay with me. I have table COMMENT that has OneToMany relationship with itself. @Entity public class Comment(){ ... @ManyToOne(optional=true, fetch=FetchType.LAZY) @JoinColumn(name="REPLYTO_ID") private Comment replyTo; @OneToMany(mappedBy="replyTo", cascade=CascadeType.ALL) private List<Comment> replies = new ArrayList<Comment>(); public void addReply(NewsFeed reply){ replies.add(reply); reply.setReplyTo(this); } public void removeReply(NewsFeed reply){ replies.remove(reply); } } So you can think like this. Each comment can have a List of replies which are also type Comment. Now it is very easy for me to delete the original comment and get the updated list back. All I need to do after delete is this. allComments = myEJB.getAllComments(); //This will query the db and return updated list But I am having problem when trying to delete replies and getting the updated list back. So here is how I delete the replies. Inside my managed bean I have //Before invoke this method, I have the value of originalFeed, and deletedFeed set. //These original comments are display inside a p:dataTable X, and the replies are //displayed inside p:dataTable Y which is inside X. So when I click the delete button //I know which comment I want to delete, and if it is the replies, I will know //which one is its original post public void deleteFeed(){ if(this.deletedFeed != null){ scholarEJB.deleteFeeds(this.deletedFeed); if(this.originalFeed != null){ //Since the originalFeed is not null, this is the `replies` //that I want to delete scholarEJB.removeReply(this.originalFeed, this.deletedFeed); } feeds = scholarEJB.findAllFeed(); } } Then inside my EJB scholarEJB, I have public void removeReply(NewsFeed comment, NewsFeed reply){ comment = em.merge(comment); comment.removeReply(reply); em.persist(comment); } public void deleteFeeds(NewsFeed e){ e = em.find(NewsFeed.class, e.getId()); em.remove(e); } When I get out, the entity (the reply) get correctly removed from the database, but inside the feeds List, reference of that reply still there. It only until I log out and log back in that the reply disappear. Please help

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  • I need help with creating a data structure in PHP

    - by alex
    What I need to do is have a data structure that shows jobs organised into 14 day periods, but only when an id is the same. I've implemented all sorts of stuff, but they have failed miserably. Ideally, maybe a SQL expert could handle all of this in the query. Here is some of my code. You can assume all library stuff works as expected. $query = 'SELECT date, rig_id, comments FROM dor ORDER BY date DESC'; $dors = Db::query(Database::SELECT, $query)->execute()->as_array(); This will return all jobs, but I need to have them organised by 14 day period with the same rig_id value. $hitches = array(); foreach($dors as $dor) { $rigId = $dor['rig_id']; $date = strtotime($dor['date']); if (empty($hitches)) { $hitches[] = array( 'rigId' => $rigId, 'startDate' => $date, 'dors' => array($dor) ); } else { $found = false; foreach($hitches as $key => $hitch) { $hitchStartDate = $hitch['startDate']; $dateDifference = abs($hitchStartDate - $date); $isSameHitchTimeFrame = $dateDifference < (Date::DAY * 14); if ($rigId == $hitch['rigId'] AND $isSameHitchTimeFrame) { $found = true; $hitches[$key]['dors'][] = $dor; } } if ($found === false) { $hitches[] = array( 'rigId' => $rigId, 'startDate' => $date, 'dors' => array($dor) ); } } } This seems to work OK splitting up by rig_id, but not by date. I also think I'm doing it wrong because I need to check the earliest date. Is it possible at all to do any of this in the database query? To recap, here is my problem I have a list of jobs with all have a rig_id (many jobs can have the same) and a date. I need the data to be organised into hitches. That is, the rig_id must be the same per hitch, and they must span a 14 day period, in which the next 14 days with the same rig_id will be a new hitch. Can someone please point me on the right track? Cheers

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  • Reading Metadata property of GifBitmapDecoder...why is it null?

    - by David
    How can I read the delay, left and top offset data for each frame of a gif? I've gotten this far. Load the Gif var myGif = new GifBitmapDecoder(uri, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad); Get a frame var frame = myGif.Frames[i]; From MSDN: Native Image Format Metadata Queries read (ushort)Metadata.GetQuery("/grctlext/Delay"), (ushort)Metadata.GetQuery("/imgdesc/Left"), (ushort)Metadata.GetQuery("/imgdesc/Top") But two things don't work. First the Metadata property of both the gif and the frame are always null, even if I try different animated gif files. Second, the Metadata property of the frame doesn't seem to have a GetQuery method. How do I run these queries, what did I miss? Edit: Here is sample code that gives me null metadata. Using a fresh install of VS2010 Premium, on a fresh WPF application. The image file is the one in the comments. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows; using System.Windows.Controls; using System.Windows.Data; using System.Windows.Documents; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Imaging; using System.Windows.Navigation; using System.Windows.Shapes; namespace WpfApplication1 { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); var uri = new Uri(@"c:\b-414328-animated_gif_.gif"); var myGif = new GifBitmapDecoder(uri, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad); var frame = myGif.Frames[0]; Title = ""; Title += "Global Metadata is null: " + (myGif.Metadata == null).ToString(); Title += "; Frame Metadata is null: " + (frame.Metadata == null).ToString(); // Crash due to null metadata //var frameData = (BitmapMetadata)frame.Metadata; //var rate = (ushort)frameData.GetQuery("/grctlext/Delay"); } } }

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  • navigator.onLine

    - by cf_PhillipSenn
    I'm playing with the incomplete example found at http://www.w3.org/TR/offline-webapps/ But I'm distressed to see comments in it like: "renders the note somewhere", and "report error", and "// …" So, will someone please help me write a valid example? Here's what I've got so far: <!DOCTYPE HTML> <html manifest="cache-manifest"> <head> <script> var db = openDatabase("notes", "", "The Example Notes App!", 1048576); function renderNote(row) { // renders the note somewhere } function reportError(source, message) { // report error } function renderNotes() { db.transaction(function(tx) { tx.executeSql('CREATE TABLE IF NOT EXISTS Notes(title TEXT, body TEXT)', []); tx.executeSql(‘SELECT * FROM Notes’, [], function(tx, rs) { for(var i = 0; i < rs.rows.length; i++) { renderNote(rs.rows[i]); } }); }); } function insertNote(title, text) { db.transaction(function(tx) { tx.executeSql('INSERT INTO Notes VALUES(?, ?)', [ title, text ], function(tx, rs) { // … }, function(tx, error) { reportError('sql', error.message); }); }); } </script> <style> label { display:block; } </style> </head> <body> <form> <label for="mytitle">Title:</label> <input name="mytitle"> <label for="mytext">Text:</label> <textarea name="mytext"></textarea> <!-- There is no submit button because I want to save the info on every keystroke --> </form> </body> </html> I also know that I have to incorporate this in there somewhere: if (navigator.onLine) { // Send data using XMLHttpRequest } else { // Queue data locally to send later } But I'm not sure what even I would tie that too.

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  • Associated models in Rails?

    - by dannymcc
    Hi Everyone, In my rails application I have two models called Kases and Notes. They work in the same way comments do with blog posts, I.e. each Kase entry can have multiple notes attached to it. I have got everything working, but for some reason I cannot get the destroy link to work for the Notes. I think I am overlooking something that is different with associated models to standard models. Notes Controller class NotesController < ApplicationController # POST /notes # POST /notes.xml def create @kase = Kase.find(params[:kase_id]) @note = @kase.notes.create!(params[:note]) respond_to do |format| format.html { redirect_to @kase } format.js end end end Kase Model class Kase < ActiveRecord::Base validates_presence_of :jobno has_many :notes Note Model class Note < ActiveRecord::Base belongs_to :kase end In the Kase show view I call a partial within /notes called _notes.html.erb: Kase Show View <div id="notes"> <h2>Notes</h2> <%= render :partial => @kase.notes %> <% form_for [@kase, Note.new] do |f| %> <p> <h3>Add a new note</h3> <%= f.text_field :body %><%= f.submit "Add Note" %> </p> <% end %> </div> /notes/_note.html.erb <% div_for note do %> <div id="sub-notes"> <p> <%= h(note.body) %><br /> <span style="font-size:smaller">Created <%= time_ago_in_words(note.created_at) %> ago on <%= note.created_at %></span> </p> <%= link_to "Remove Note", kase_path(@kase), :confirm => 'Are you sure?', :method => :delete, :class => 'important' %> </div> <% end %> As you can see, I have a Remove Note destroy link, but that destroys the entire Kase the note is associated with. How do I make the destroy link remove only the note? <%= link_to "Remove Note", kase_path(@kase), :confirm => 'Are you sure?', :method => :delete, :class => 'important' %> Any help would, as always, be greatly appreciated! Thanks, Danny

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  • Zaypay alternatives for payments using call or sms

    - by JohannesH
    We are currently trying to implement a payment provider in zaypay for paying for services using sms or by calling a number. We already have google checkout and paypal working for regular payments but zaypay is rather inflexible, poorly documented and a pain to setup when you have hundreds of products with varying prices. So my question is, do you know of any other european payment providers that take sms and call payments? As a response to Roberts answer/question Hi Robert, I must say that the Zaypay solution is the best and only I've seen thus far regarding phoned payments. However, since its now 2 months ago I finished the implementation of our custom Zaypay UI I can't remember much of the the details of the problems we were having. I'll try to give a brief of them anyways the best I can. First of all I would like to see a redirection type scenario for payalogues. From what I remember you guys are using the JS framework "Prototype" which doesn't play nice with jQuery which we are using so we weren't able to use the popup-type scenario supported by payalogues. Furthermore when implementing our custom interface I remember a lot of missing translations, like words that were codes instead of a word or a phrase. This meant we ended up writing/translating all the messages we needed ourselves. Also, another point of annoyance was the setup of prices and items. I wish we could just send in the order items/prices as a part of the interface like you can in Google Checkout or PayPal (not that they're flawless either), instead of having to define ALL the items you will ever sell through your admin interface beforehand. As far as I can remember it is virtually impossible to use Zaypay for a multi-item order in its current form. Finally there are, as far as I can tell, some security issues that you have to think about when you implement a custom solution... especially a ajax driven one. As I said in my original post you do mention this in the documentation but I believe the documentation wasn't that comprehensive regarding security issues. Again I wish I could give more details but the code & client is long since gone, so I can't look up the comments I wrote. Sorry! Oh yeah, the general API documentation weren't exactly comprehensive and 100% correct either. Again, I don't want to advice people against using Zaypay, I just want to advice that they should try it out first on a realistic prototype and think about their implementation before releasing to production. Maybe its just me who misunderstood a lot of things but I generally had a difficult time using your framework and I was left with a feeling that the API was very new and not thought through from the beginning.

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  • JPA Entity Manager resource handling

    - by chiragshahkapadia
    Every time I call JPA method its creating entity and binding query. My persistence properties are: <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/> <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.SingletonEhCacheProvider"/> <property name="hibernate.cache.use_second_level_cache" value="true"/> <property name="hibernate.cache.use_query_cache" value="true"/> And I am creating entity manager the way shown below: emf = Persistence.createEntityManagerFactory("pu"); em = emf.createEntityManager(); em = Persistence.createEntityManagerFactory("pu").createEntityManager(); Is there any nice way to manage entity manager resource instead create new every time or any property can set in persistence. Remember it's JPA. See below binding log every time : 15:35:15,527 INFO [AnnotationBinder] Binding entity from annotated class: * 15:35:15,527 INFO [QueryBinder] Binding Named query: * = * 15:35:15,527 INFO [QueryBinder] Binding Named query: * = * 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [EntityBinder] Bind entity com.* on table * 15:35:15,542 INFO [HibernateSearchEventListenerRegister] Unable to find org.hibernate.search.event.FullTextIndexEventListener on the classpath. Hibernate Search is not enabled. 15:35:15,542 INFO [NamingHelper] JNDI InitialContext properties:{} 15:35:15,542 INFO [DatasourceConnectionProvider] Using datasource: 15:35:15,542 INFO [SettingsFactory] RDBMS: and Real Application Testing options 15:35:15,542 INFO [SettingsFactory] JDBC driver: Oracle JDBC driver, version: 9.2.0.1.0 15:35:15,542 INFO [Dialect] Using dialect: org.hibernate.dialect.Oracle10gDialect 15:35:15,542 INFO [TransactionFactoryFactory] Transaction strategy: org.hibernate.transaction.JDBCTransactionFactory 15:35:15,542 INFO [TransactionManagerLookupFactory] No TransactionManagerLookup configured (in JTA environment, use of read-write or transactional second-level cache is not recomm ended) 15:35:15,542 INFO [SettingsFactory] Automatic flush during beforeCompletion(): disabled 15:35:15,542 INFO [SettingsFactory] Automatic session close at end of transaction: disabled 15:35:15,542 INFO [SettingsFactory] JDBC batch size: 15 15:35:15,542 INFO [SettingsFactory] JDBC batch updates for versioned data: disabled 15:35:15,542 INFO [SettingsFactory] Scrollable result sets: enabled 15:35:15,542 INFO [SettingsFactory] JDBC3 getGeneratedKeys(): disabled 15:35:15,542 INFO [SettingsFactory] Connection release mode: auto 15:35:15,542 INFO [SettingsFactory] Default batch fetch size: 1 15:35:15,542 INFO [SettingsFactory] Generate SQL with comments: disabled 15:35:15,542 INFO [SettingsFactory] Order SQL updates by primary key: disabled 15:35:15,542 INFO [SettingsFactory] Order SQL inserts for batching: disabled 15:35:15,542 INFO [SettingsFactory] Query translator: org.hibernate.hql.ast.ASTQueryTranslatorFactory 15:35:15,542 INFO [ASTQueryTranslatorFactory] Using ASTQueryTranslatorFactory 15:35:15,542 INFO [SettingsFactory] Query language substitutions: {} 15:35:15,542 INFO [SettingsFactory] JPA-QL strict compliance: enabled 15:35:15,542 INFO [SettingsFactory] Second-level cache: enabled 15:35:15,542 INFO [SettingsFactory] Query cache: enabled 15:35:15,542 INFO [SettingsFactory] Cache region factory : org.hibernate.cache.impl.bridge.RegionFactoryCacheProviderBridge 15:35:15,542 INFO [RegionFactoryCacheProviderBridge] Cache provider: net.sf.ehcache.hibernate.SingletonEhCacheProvider 15:35:15,542 INFO [SettingsFactory] Optimize cache for minimal puts: disabled 15:35:15,542 INFO [SettingsFactory] Structured second-level cache entries: disabled 15:35:15,542 INFO [SettingsFactory] Query cache factory: org.hibernate.cache.StandardQueryCacheFactory 15:35:15,542 INFO [SettingsFactory] Statistics: disabled 15:35:15,542 INFO [SettingsFactory] Deleted entity synthetic identifier rollback: disabled 15:35:15,542 INFO [SettingsFactory] Default entity-mode: pojo 15:35:15,542 INFO [SettingsFactory] Named query checking : enabled 15:35:15,542 INFO [SessionFactoryImpl] building session factory 15:35:15,542 INFO [SessionFactoryObjectFactory] Not binding factory to JNDI, no JNDI name configured 15:35:15,542 INFO [UpdateTimestampsCache] starting update timestamps cache at region: org.hibernate.cache.UpdateTimestampsCache 15:35:15,542 INFO [StandardQueryCache] starting query cache at region: org.hibernate.cache.StandardQueryCache

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  • Linq to sql C# updating reference Tables

    - by Laurence Burke
    ok reclarification I am adding a new address and I know the structure as AddressID = PK and all other entities are non nullable. Now on insert of a new row the addrID Pk is autogened and I am wondering if I would have to get that to create a new row in the referencing table or does that automatically get generated also. also I want to be able to repopulate the dropdownlist that lists the current employee's addresses with the newly created address. static uint _curEmpID; protected void btnAdd_Click(object sender, EventArgs e) { if (txtZip.Text != "" && txtAdd1.Text != "" && txtCity.Text != "") { TestDataClassDataContext dc = new TestDataClassDataContext(); Address addr = new Address() { AddressLine1 = txtAdd1.Text, AddressLine2 = txtAdd2.Text, City = txtCity.Text, PostalCode = txtZip.Text, StateProvinceID = Convert.ToInt32(ddlState.SelectedValue) }; dc.Addresses.InsertOnSubmit(addr); lblSuccess.Visible = true; lblErrMsg.Visible = false; dc.SubmitChanges(); // // TODO: add reference from new address to CurEmp Table // SetAddrList(); } else { lblErrMsg.Text = "Invalid Input"; lblErrMsg.Visible = true; } } protected void ddlAddList_SelectedIndexChanged(object sender, EventArgs e) { lblErrMsg.Visible = false; lblSuccess.Visible = false; TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; if (ddlAddList.SelectedValue != "-1") { var addr = (from a in dc.Addresses where a.AddressID == Convert.ToInt32(ddlAddList.SelectedValue) select a).FirstOrDefault(); txtAdd1.Text = addr.AddressLine1; txtAdd2.Text = addr.AddressLine2; txtCity.Text = addr.City; txtZip.Text = addr.PostalCode; ddlState.SelectedValue = addr.StateProvinceID.ToString(); btnSubmit.Visible = true; btnAdd.Visible = false; } else { txtAdd1.Text = ""; txtAdd2.Text = ""; txtCity.Text = ""; txtZip.Text = ""; btnAdd.Visible = true; btnSubmit.Visible = false; } } protected void SetAddrList() { TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; var addList = from addr in dc.Addresses from eaddr in dc.EmployeeAddresses where eaddr.EmployeeID == _curEmpID && addr.AddressID == eaddr.AddressID select new { AddValue = addr.AddressID, AddText = addr.AddressID, }; ddlAddList.DataSource = addList; ddlAddList.DataValueField = "AddValue"; ddlAddList.DataTextField = "AddText"; ddlAddList.DataBind(); ddlAddList.Items.Add(new ListItem("<Add Address>", "-1")); } OK I am hoping that I did not include too much code. I would really appreciate any other comments about I could otherwise improve this code in any other ways also.

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  • How safe is my safe rethrow?

    - by gustafc
    (Late edit: This question will hopefully be obsolete when Java 7 comes, because of the "final rethrow" feature which seems like it will be added.) Quite often, I find myself in situations looking like this: do some initialization try { do some work } catch any exception { undo initialization rethrow exception } In C# you can do it like this: InitializeStuff(); try { DoSomeWork(); } catch { UndoInitialize(); throw; } For Java, there's no good substitution, and since the proposal for improved exception handling was cut from Java 7, it looks like it'll take at best several years until we get something like it. Thus, I decided to roll my own: (Edit: Half a year later, final rethrow is back, or so it seems.) public final class Rethrow { private Rethrow() { throw new AssertionError("uninstantiable"); } /** Rethrows t if it is an unchecked exception. */ public static void unchecked(Throwable t) { if (t instanceof Error) throw (Error) t; if (t instanceof RuntimeException) throw (RuntimeException) t; } /** Rethrows t if it is an unchecked exception or an instance of E. */ public static <E extends Exception> void instanceOrUnchecked( Class<E> exceptionClass, Throwable t) throws E, Error, RuntimeException { Rethrow.unchecked(t); if (exceptionClass.isInstance(t)) throw exceptionClass.cast(t); } } Typical usage: public void doStuff() throws SomeException { initializeStuff(); try { doSomeWork(); } catch (Throwable t) { undoInitialize(); Rethrow.instanceOrUnchecked(SomeException.class, t); // We shouldn't get past the above line as only unchecked or // SomeException exceptions are thrown in the try block, but // we don't want to risk swallowing an error, so: throw new SomeException("Unexpected exception", t); } private void doSomeWork() throws SomeException { ... } } It's a bit wordy, catching Throwable is usually frowned upon, I'm not really happy at using reflection just to rethrow an exception, and I always feel a bit uneasy writing "this will not happen" comments, but in practice it works well (or seems to, at least). What I wonder is: Do I have any flaws in my rethrow helper methods? Some corner cases I've missed? (I know that the Throwable may have been caused by something so severe that my undoInitialize will fail, but that's OK.) Has someone already invented this? I looked at Commons Lang's ExceptionUtils but that does other things. Edit: finally is not the droid I'm looking for. I'm only interested to do stuff when an exception is thrown. Yes, I know catching Throwable is a big no-no, but I think it's the lesser evil here compared to having three catch clauses (for Error, RuntimeException and SomeException, respectively) with identical code. Note that I'm not trying to suppress any errors - the idea is that any exceptions thrown in the try block will continue to bubble up through the call stack as soon as I've rewinded a few things.

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  • Choosing the right .NET architecture. WCF? WPF/Forms, ASP.NET (MVC)?

    - by Tommy Jakobsen
    I’m in the situation that I have to design and implement a rather big system from the bottom. I’m having some (a lot actually) questions about the architecture that I would like your comments and thoughts on. I don’t hope that I’ve written too much here, but I wanted to give you all an idea of what the system is. Quick info about the applications, read if you want: I can’t share much detail about the project, but basically it’s a system where we offer our customer a service to manage their users. We have a hotline where the users call and our hotline uses an (windows) application (intranet) to manage the user’s data, etc. The customer also has a web application where they can see reports, information about their business and users, and the ability to modify their data. Modifying data is not just user data like address and so, but also information about the products/services the user has, which can be complicated. The applications will be built on Microsoft .NET Framework 4, with a MS SQL Server 2008 database. There will be a few applications that have to access this database, such as: Intranet application (used by us and our hotline) Customer web application type 1 Customer web application type 2 Customer web application type n different applications) … Now my big problem is what .NET parts I should use for such a system. For the “backend” I’ve considered using Windows Communication Foundation: Would WCF be a good choice? The intranet application will be an application that has to edit lots of records in the database. It has to be easy to navigate using the keyboard (fast to work with). Has a feature such as “find customer, find that, lookup this, choose this and update that”. What would be the best choice to develop this application in? Would it be WPF or good old Windows Forms? I don’t need all of the fancy graphics features in WPF, like 3D, but the application has to look nice (maybe something like the new Visual Studio/Office tools). And the same question goes for the web pages. They have much the same work to do, but not as many features as the intranet application, and not the same amount of data (much less). That is my questions for now. I’m hoping to get a discussion going that will open my eyes to some of these technologies, helping me decide architecture to go with. I would like to say thanks in advance, and let you all know that any thoughts will be much appreciated.

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  • Adding rows with linq trouble with reference table

    - by Laurence Burke
    I am adding a new address and I know the structure as AddressID = PK and all other entities are non nullable. Now on insert of a new row the addrID Pk is autogened and I am wondering if I would have to get that to create a new row in the referencing table EmployeeAddress or does that automatically get generated also. also I want to be able to repopulate the dropdownlist that lists the current employee's addresses with the newly created address. static uint _curEmpID; protected void btnAdd_Click(object sender, EventArgs e) { if (txtZip.Text != "" && txtAdd1.Text != "" && txtCity.Text != "") { TestDataClassDataContext dc = new TestDataClassDataContext(); Address addr = new Address() { AddressLine1 = txtAdd1.Text, AddressLine2 = txtAdd2.Text, City = txtCity.Text, PostalCode = txtZip.Text, StateProvinceID = Convert.ToInt32(ddlState.SelectedValue) }; dc.Addresses.InsertOnSubmit(addr); lblSuccess.Visible = true; lblErrMsg.Visible = false; dc.SubmitChanges(); // // TODO: insert new row in EmployeeAddress to reference CurEmp to newly created address // SetAddrList(); } else { lblErrMsg.Text = "Invalid Input"; lblErrMsg.Visible = true; } } protected void ddlAddList_SelectedIndexChanged(object sender, EventArgs e) { lblErrMsg.Visible = false; lblSuccess.Visible = false; TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; if (ddlAddList.SelectedValue != "-1") { var addr = (from a in dc.Addresses where a.AddressID == Convert.ToInt32(ddlAddList.SelectedValue) select a).FirstOrDefault(); txtAdd1.Text = addr.AddressLine1; txtAdd2.Text = addr.AddressLine2; txtCity.Text = addr.City; txtZip.Text = addr.PostalCode; ddlState.SelectedValue = addr.StateProvinceID.ToString(); btnSubmit.Visible = true; btnAdd.Visible = false; } else { txtAdd1.Text = ""; txtAdd2.Text = ""; txtCity.Text = ""; txtZip.Text = ""; btnAdd.Visible = true; btnSubmit.Visible = false; } } protected void SetAddrList() { TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; var addList = from addr in dc.Addresses from eaddr in dc.EmployeeAddresses where eaddr.EmployeeID == _curEmpID && addr.AddressID == eaddr.AddressID select new { AddValue = addr.AddressID, AddText = addr.AddressID, }; ddlAddList.DataSource = addList; ddlAddList.DataValueField = "AddValue"; ddlAddList.DataTextField = "AddText"; ddlAddList.DataBind(); ddlAddList.Items.Add(new ListItem("<Add Address>", "-1")); } OK I am hoping that I did not include too much code. I would really appreciate any other comments about I could otherwise improve this code in any other ways also.

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  • Django Multi-Table Inheritance VS Specifying Explicit OneToOne Relationship in Models

    - by chefsmart
    Hope all this makes sense :) I'll clarify via comments if necessary. Also, I am experimenting using bold text in this question, and will edit it out if I (or you) find it distracting. With that out of the way... Using django.contrib.auth gives us User and Group, among other useful things that I can't do without (like basic messaging). In my app I have several different types of users. A user can be of only one type. That would easily be handled by groups, with a little extra care. However, these different users are related to each other in hierarchies / relationships. Let's take a look at these users: - Principals - "top level" users Administrators - each administrator reports to a Principal Coordinators - each coordinator reports to an Administrator Apart from these there are other user types that are not directly related, but may get related later on. For example, "Company" is another type of user, and can have various "Products", and products may be supervised by a "Coordinator". "Buyer" is another kind of user that may buy products. Now all these users have various other attributes, some of which are common to all types of users and some of which are distinct only to one user type. For example, all types of users have to have an address. On the other hand, only the Principal user belongs to a "BranchOffice". Another point, which was stated above, is that a User can only ever be of one type. The app also needs to keep track of who created and/or modified Principals, Administrators, Coordinators, Companies, Products etc. (So that's two more links to the User model.) In this scenario, is it a good idea to use Django's multi-table inheritance as follows: - from django.contrib.auth.models import User class Principal(User): # # # branchoffice = models.ForeignKey(BranchOffice) landline = models.CharField(blank=True, max_length=20) mobile = models.CharField(blank=True, max_length=20) created_by = models.ForeignKey(User, editable=False, blank=True, related_name="principalcreator") modified_by = models.ForeignKey(User, editable=False, blank=True, related_name="principalmodifier") # # # Or should I go about doing it like this: - class Principal(models.Model): # # # user = models.OneToOneField(User, blank=True) branchoffice = models.ForeignKey(BranchOffice) landline = models.CharField(blank=True, max_length=20) mobile = models.CharField(blank=True, max_length=20) created_by = models.ForeignKey(User, editable=False, blank=True, related_name="principalcreator") modified_by = models.ForeignKey(User, editable=False, blank=True, related_name="principalmodifier") # # # Please keep in mind that there are other user types that are related via foreign keys, for example: - class Administrator(models.Model): # # # principal = models.ForeignKey(Principal, help_text="The supervising principal for this Administrator") user = models.OneToOneField(User, blank=True) province = models.ForeignKey( Province) landline = models.CharField(blank=True, max_length=20) mobile = models.CharField(blank=True, max_length=20) created_by = models.ForeignKey(User, editable=False, blank=True, related_name="administratorcreator") modified_by = models.ForeignKey(User, editable=False, blank=True, related_name="administratormodifier") I am aware that Django does use a one-to-one relationship for multi-table inheritance behind the scenes. I am just not qualified enough to decide which is a more sound approach.

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  • Possible bug with tabified QDockWidget and setFloating()

    - by krunk
    I've run into some odd behavior with tabified QDockWidgets, below is an example program with comments that demonstrates the behavior. Is this a bug or is it expected behavior and I'm missing some nuance in QDockWidget that causes this? Directly, since this does not work, how would one properly "undock" a hidden QDockWidget then display it? #include <QApplication> #include <QMainWindow> #include <QAction> #include <QDockWidget> #include <QMenu> #include <QSize> #include <QMenuBar> using namespace std; int main (int argc, char* argv[]) { QApplication app(argc, argv); QMainWindow window; QDockWidget dock1(&window); QDockWidget dock2(&window); QMenu menu("View"); dock1.setAllowedAreas(Qt::LeftDockWidgetArea | Qt::RightDockWidgetArea); dock2.setAllowedAreas(Qt::LeftDockWidgetArea | Qt::RightDockWidgetArea); dock1.setWindowTitle("Dock One"); dock2.setWindowTitle("Dock Two"); window.addDockWidget(Qt::RightDockWidgetArea, &dock1); window.addDockWidget(Qt::RightDockWidgetArea, &dock2); window.menuBar()->addMenu(&menu); window.setMinimumSize(QSize(800, 600)); window.tabifyDockWidget(&dock1, &dock2); dock1.hide(); dock2.hide(); menu.addAction(dock1.toggleViewAction()); menu.addAction(dock2.toggleViewAction()); window.show(); // Below is where the oddness starts. It seems to only exhibit the // behavior if the dock widgets are tabified. // Odd behavior here // This does not work. the window never shows, though its menu action shows // checked. Not only does this window not show up, but all toggle actions // for all dock windows (e.g. dock1 and dock2) are broken for the duration // of the application loop. // dock1.setFloating(true); // dock1.show(); // This does work. . . of course only if you do _not_ run the above first. // however, you can often get a little lag or "blip" in the rendering as // the dock is shown docked before setFloating is set to true. dock1.show(); dock1.setFloating(true); return app.exec(); }

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  • What Regex can strip e.g. "note:" and "firstName: " from the left of a string?

    - by Edward Tanguay
    I need to strip the "label" off the front of strings, e.g. note: this is a note needs to return: note and this is a note I've produced the following code example but am having trouble with the regexes. What code do I need in the two ???????? areas below so that I get the desired results shown in the comments? using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Text.RegularExpressions; namespace TestRegex8822 { class Program { static void Main(string[] args) { List<string> lines = new List<string>(); lines.Add("note: this is a note"); lines.Add("test: just a test"); lines.Add("test:\t\t\tjust a test"); lines.Add("firstName: Jim"); //"firstName" IS a label because it does NOT contain a space lines.Add("She said this to him: follow me."); //this is NOT a label since there is a space before the colon lines.Add("description: this is the first description"); lines.Add("description:this is the second description"); //no space after colon lines.Add("this is a line with no label"); foreach (var line in lines) { Console.WriteLine(StringHelpers.GetLabelFromLine(line)); Console.WriteLine(StringHelpers.StripLabelFromLine(line)); Console.WriteLine("--"); //note //this is a note //-- //test //just a test //-- //test //just a test //-- //firstName //Jim //-- // //She said this to him: follow me. //-- //description //this is the first description //-- //description //this is the first description //-- // //this is a line with no label //-- } Console.ReadLine(); } } public static class StringHelpers { public static string GetLabelFromLine(this string line) { string label = line.GetMatch(@"^?:(\s)"); //??????????????? if (!label.IsNullOrEmpty()) return label; else return ""; } public static string StripLabelFromLine(this string line) { return ...//??????????????? } public static bool IsNullOrEmpty(this string line) { return String.IsNullOrEmpty(line); } } public static class RegexHelpers { public static string GetMatch(this string text, string regex) { Match match = Regex.Match(text, regex); if (match.Success) { string theMatch = match.Groups[0].Value; return theMatch; } else { return null; } } } }

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  • maven-compiler-plugin exclude

    - by easyrider
    Hi, I have a following Problem. I would like to exclude some .java files (*/jsfunit/.java) during test-compile phace and on the other side i would like to include them during compile phace (id i start tomact with tomcat:run goal) My pom.xml <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.6</source> <target>1.6</target> <!-- <excludes> <exclude>**/*JSFIntegration*.java</exclude> </excludes> --> </configuration> <executions> <!-- <execution> <id>default-compile</id> <phase>compile</phase> <goals> <goal>compile</goal> </goals> <configuration> <includes> <include>**/jsfunit/*.java</include> </includes> </configuration> </execution>--> <execution> <id>default-testCompile</id> <phase>test-compile</phase> <configuration> <excludes> <exclude>**/jsfunit/*.java</exclude> </excludes> </configuration> <goals> <goal>testCompile</goal> </goals> </execution> </executions> </plugin> But it does not work : exclude in default-testCompile execution does not filter these classes. If i remove the comments then all classes matched */jsfunit/.java would be compiled but only if i touch them! Please help! Thanx in advance

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  • Keeping track of business rules within IT department?

    - by evaldas-alexander
    I am looking for the best way to keep track of the business rules for both developers and everybody else (support staff / management) in a startup enviroment. The challenge is that our business model requires quite a lot of different business rules, which are created pretty much on the fly and evolving organically after that. After running this project for 3+ years, we have so many of such rules that often the only way to be sure about what the application is supposed to do in a certain situation is to go find the module responsible for that process and analyze its code and comments. That is all fine as long as you have one single developer who created the entire application from the scratch, but every new developer needs to go over pretty much entire codebase in order to understand how the application works. Even bigger problem is that non technical employees don't even have that option and therefore are forced to ask me pretty much every day how some certain case would be handled by the application. Quick example - we only start charging for our customer campaigns once they have been active for at least 72 hours, but at the same time we stop creating invoices for campaigns that belong to insolvent accounts and close such accounts within a month of the first failed charge. That does not apply to accounts that are set to "non-chargeable" which most commonly belongs to us since we are using the service ourselves. The invoices are created on the 1st of each month and include charges from the previous month + any current balance that the account might have. However, some customers are charged only 4 days after their invoice has been generated due to issues with their billing department. In addition to that, invoices are also created when customer deactivates his campaign, but that can only be done once the campaign is not longer under mandatory 6 month contract, unless account manager approves early deactivation. I know, that's quite a lot of rules that need to be taken into account when answering a question "when do we bill our customers", but actually I could still append an asterisk at the end of each sentence in order to disclose some rare exceptions. Of course, it would be easiest just to keep the business rules to the minimum, but we need to adapt to changing marketplace - i.e. less than a year ago we had no contracts whatsoever. One idea that I had so far was a simplistic wiki with categories corresponding to areas such as "Account activation", "Invoicing", "Collection procedures" and so on. Another idea would be to have giant interactive flowchart showing the entire customer "life cycle" from prospecting to account deactivation. What are your experiences / suggestions?

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  • The Math of a Jump in a 2D game.

    - by ONi
    I have been all around with this question and I can't find the correct answer! So, behold, the description of my question: I'm working in J2ME, I have my gameloop that do the following: public void run() { Graphics g = this.getGraphics(); while (running) { long diff = System.currentTimeMillis() - lastLoop; lastLoop = System.currentTimeMillis(); input(); this.level.doLogic(); render(g, diff); try { Thread.sleep(10); } catch (InterruptedException e) { stop(e); } } } so it's just a basic gameloop, the doLogic() function calls for all the logic functions of the characters in the scene and render(g, diff) calls the animateChar function of every character on scene, following this, the animChar function in the Character class sets up everything in the screen as this: protected void animChar(long diff) { this.checkGravity(); this.move((int) ((diff * this.dx) / 1000), (int) ((diff * this.dy) / 1000)); if (this.acumFrame > this.framerate) { this.nextFrame(); this.acumFrame = 0; } else { this.acumFrame += diff; } } This ensures me that everything must to move according to the time that the machine takes to go from cycle to cycle (remember it's a phone, not a gaming rig). I'm sure it's not the most efficient way to achieve this behavior so I'm totally open for criticism of my programming skills in the comments, but here my problem: When I make I character jump, what I do is that I put his dy to a negative value, say -200 and I set the boolean jumping to true, that makes the character go up, and then I have this function called checkGravity() that ensure that everything that goes up has to go down, checkGravity also checks for the character being over platforms so I will strip it down a little for the sake of your time: public void checkGravity() { if (this.jumping) { this.jumpSpeed += 10; if (this.jumpSpeed > 0) { this.jumping = false; this.falling = true; } this.dy = this.jumpSpeed; } if (this.falling) { this.jumpSpeed += 10; if (this.jumpSpeed > 200) this.jumpSpeed = 200; this.dy = this.jumpSpeed; if (this.collidesWithPlatform()) { this.falling = false; this.standing = true; this.jumping = false; this.jumpSpeed = 0; this.dy = this.jumpSpeed; } } } So, the problem is, that this function updates the dy regardless of the diff, making the characters fly like Superman in slow machines, and I have no idea how to implement the diff factor so that when a character is jumping, his speed decrement in a proportional way to the game speed. Can anyone help me fix this issue? or give me pointers on how to make a 2D Jump in J2ME the right way. Thank you very much for your time.

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  • How can I structure and recode messy categorical data in R?

    - by briandk
    I'm struggling with how to best structure categorical data that's messy, and comes from a dataset I'll need to clean. The Coding Scheme I'm analyzing data from a university science course exam. We're looking at patterns in student responses, and we developed a coding scheme to represent the kinds of things students are doing in their answers. A subset of the coding scheme is shown below. Note that within each major code (1, 2, 3) are nested non-unique sub-codes (a, b, ...). What the Raw Data Looks Like I've created an anonymized, raw subset of my actual data which you can view here. Part of my problem is that those who coded the data noticed that some students displayed multiple patterns. The coders' solution was to create enough columns (reason1, reason2, ...) to hold students with multiple patterns. That becomes important because the order (reason1, reason2) is arbitrary--two students (like student 41 and student 42 in my dataset) who correctly applied "dependency" should both register in an analysis, regardless of whether 3a appears in the reason column or the reason2 column. How Can I Best Structure Student Data? Part of my problem is that in the raw data, not all students display the same patterns, or the same number of them, in the same order. Some students may do just one thing, others may do several. So, an abstracted representation of example students might look like this: Note in the example above that student002 and student003 both are coded as "1b", although I've deliberately shown the order as different to reflect the reality of my data. My (Practical) Questions Should I concatenate reason1, reason2, ... into one column? How can I (re)code the reasons in R to reflect the multiplicity for some students? Thanks I realize this question is as much about good data conceptualization as it is about specific features of R, but I thought it would be appropriate to ask it here. If you feel it's inappropriate for me to ask the question, please let me know in the comments, and stackoverflow will automatically flood my inbox with sadface emoticons. If I haven't been specific enough, please let me know and I'll do my best to be clearer.

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  • Design Technique: How to design a complex system for processing orders, products and units.

    - by Shyam
    Hi, Programming is fun: I learned that by trying out simple challenges, reading up some books and following some tutorials. I am able to grasp the concepts of writing with OO (I do so in Ruby), and write a bit of code myself. What bugs me though is that I feel re-inventing the wheel: I haven't followed an education or found a book (a free one that is) that explains me the why's instead of the how's, and I've learned from the A-team that it is the plan that makes it come together. So, armed with my nuby Ruby skills, I decided I wanted to program a virtual store. I figured out the following: My virtual Store will have: Products and Services Inventories Orders and Shipping Customers Now this isn't complex at all. With the help of some cool tools (CMapTools), I drew out some concepts, but quickly enough (thanks to my inferior experience in designing), my design started to bite me. My very first product-line were virtual "laptops". So, I created a class (Ruby): class Product attr_accessor :name, :price def initialize(name, price) @name = name @price = price end end which can be instantiated by doing (IRb) x = Product.new("Banana Pro", 250) Since I want my virtual customers to be able to purchase more than one product, or various types, I figured out I needed some kind of "Order" mechanism. class Order def initialize(order_no) @order_no = order_no @line_items = [] end def add_product(myproduct) @line_items << myproduct end def show_order() puts @order_no @line_items.each do |x| puts x.name.to_s + "\t" + x.price.to_s end end end that can be instantiated by doing (IRb) z = Order.new(1234) z.add_product(x) z.show_order Splendid, I have now a very simple ordering system that allows me to add products to an order. But, here comes my real question. What if I have three models of my product (economy, business, showoff)? Or have my products be composed out of separate units (bigger screen, nicer keyboard, different OS)? Surely I could make them three separate products, or add complexity to my product class, but I am looking for are best practices to design a flexible product object that can be used in the real world, to facilitate a complex system. My apologies if my grammar and my spelling are with error, as english is not my first language and I took the time to check as far I could understand and translate properly! Thank you for your answers, comments and feedback!

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  • Creating a music catalog and extracting first 30 seconds as soon as the first words are sung

    - by Rad
    I already read a question: Separation of singing voice from music. I don’t need this complex audio processing. I only need some detection mechanism that would detect that there is some voice/vocal playing while the music is playing (or not playing) I need to extract first 30 seconds when a vocalist starts singing along with full band music. See question 2 below. I want to create a music catalog using ASP.NET MVC 2 and Silverlight clients and C#.NET 4.0 programming language that would be front store. On the backend I would also like to create a desktop WPF/Windows application to create the music catalog from already existing music files, most of which have metadata in them ID3v1, ID3v2.3, ID3v2.4, iTunes MP4, WMA, Vorbis Comments and APE Tags etc. I would possibly like to create a web service that would allow catalog contributors to upload a zipped album and trigger metadata extraction of music data and extraction of music segments as described below. I would be happy if I achieve no. 1 below. Let's say I have 1000ths of songs in mp3 (or other formats) grouped in subfolders using some classification (Genre, Artists, Albums, Composers or other groupings). I want to create tables in DB that would organize songs so they can be searched based on different criteria (year, length, above classification or by song title, description etc) like what iTune store allows to their customers. I want to extract metadata from various formats (I will try to get songs in mp3 format, but there may be other popular formats) and allow music Catalog manager person to add missing data from either desktop or web applications. He or other contributors can upload zipped music via an HTML or Silverlight upload or WPF. Can anybody suggest open source libraries, articles, code snippets that can do that in an automatic way using .NET and possibly SQL Server DB? My main questions are these. This is an audio processing challenge. I want to extract 2 segments of music (questions 1 and 2): 1. How to extract a music segment: 1-2 seconds before a vocal starts singing and up to 30 seconds from that point in time and 2. Much more challenging is to find repeating segments (One would usually find or recognize the names of the songs and songs are usually known by these refrains. How would I go about creating a list of songs that go great together like what Genius from iTune does? Is there any characteristics of music that can be used to match songs? The goal is for people quickly scan and recognize songs i.e. associate melody, words with a title/album so they can make intelligent decisions like buying a song, create similar mood songs.

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  • transforming binary data using ssis and sql server 2008

    - by Rick
    Hello All - I have a task to import/transform and extract zipped binary files that contain both text data as well as embeded binary data. Within the data is data that is relational in nature and needs to be processed into a defined database structure. Currently I have a C# single threaded app that essentially grabs all the files from the directory (currently there is 13K files of varying sizes) and extracts the data on a single thread line by line inserts to the database. As you could imagine this is a very slow process and unacceptable. There are several different parsing routines used depending on the header record in the file. There are potentially upto a million rows per file when all the data is extracted to the row level of detail. Follow on task is to parse those rows into their appropriate tables based on is content. i.e. the textual content has to be parsed further into "buckets" of like data in the database. That about sums up the big picture. Now for the problem task list. How do i iterate through a packet of data using SSIS? In the app the file is decompressed and then is parsed using streams data type and byte arrays and is routed to the required parsing routine based on the header data of each packet. There is bit swapping involved as well. Should i wrap up the app code into a script task(s) and let it do the custom processing? The data is seperated by year and the sql server tables is partitioned by year as well. I need to be able to "catch" bad file data as well and process by hand most likely. Should i simply load the zipped file to sql as a blob and parse the file with T-SQL? Would that be multi threaded if done that way? Not sure how to do the parsing in tsql that is involved here. Which do you think would be faster? Potentially the data that is currently processed via files could come to us via a socket. Can SSIS collect that data in real time? How would i go about setting that up? Processing these new files from the directorys will become a daily task. I can manage the data once i get it to sql server. Getting it there in a timely fashion seems to be the long pole in the tent for me. I would appreciate any comments or suggestions from the group. Rick

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  • Instagram API and Zend/Loader.php

    - by Jaemin Kim
    I want to use Instagram API and I found this code. <html> <head></head> <body> <h1>Popular on Instagram</h1> <?php // load Zend classes require_once 'Zend/Loader.php'; Zend_Loader::loadClass('Zend_Http_Client'); // define consumer key and secret // available from Instagram API console $CLIENT_ID = 'YOUR-CLIENT-ID'; $CLIENT_SECRET = 'YOUR-CLIENT-SECRET'; try { // initialize client $client = new Zend_Http_Client('https://api.instagram.com/v1/media/popular'); $client->setParameterGet('client_id', $CLIENT_ID); // get popular images // transmit request and decode response $response = $client->request(); $result = json_decode($response->getBody()); // display images $data = $result->data; if (count($data) > 0) { echo '<ul>'; foreach ($data as $item) { echo '<li style="display: inline-block; padding: 25px"><a href="' . $item->link . '"><img src="' . $item->images->thumbnail->url . '" /></a> <br/>'; echo 'By: <em>' . $item->user->username . '</em> <br/>'; echo 'Date: ' . date ('d M Y h:i:s', $item->created_time) . '<br/>'; echo $item->comments->count . ' comment(s). ' . $item->likes->count . ' likes. </li>'; } echo '</ul>'; } } catch (Exception $e) { echo 'ERROR: ' . $e->getMessage() . print_r($client); exit; } ?> </body> </html> In here, I found Zender/Load.php, and I've never heard about that. Is it okay to go http://www.zend.com/en/products/guard/downloads here, and download Zend for linux?? And for another question, is this code available to use Instagram API?? For last, could you let me know that is there any simple code to use Instagram API? Thank you.

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  • mounting ext4 fs with block size of 65536

    - by seaquest
    I am doing some benchmarking on EXT4 performance on Compact Flash media. I have created an ext4 fs with block size of 65536. however I can not mount it on ubuntu-10.10-netbook-i386. (it is already mounting ext4 fs with 4096 bytes of block sizes) According to my readings on ext4 it should allow such big block sized fs. I want to hear your comments. root@ubuntu:~# mkfs.ext4 -b 65536 /dev/sda3 Warning: blocksize 65536 not usable on most systems. mke2fs 1.41.12 (17-May-2010) mkfs.ext4: 65536-byte blocks too big for system (max 4096) Proceed anyway? (y,n) y Warning: 65536-byte blocks too big for system (max 4096), forced to continue Filesystem label= OS type: Linux Block size=65536 (log=6) Fragment size=65536 (log=6) Stride=0 blocks, Stripe width=0 blocks 19968 inodes, 19830 blocks 991 blocks (5.00%) reserved for the super user First data block=0 1 block group 65528 blocks per group, 65528 fragments per group 19968 inodes per group Writing inode tables: done Creating journal (1024 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 37 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. root@ubuntu:~# tune2fs -l /dev/sda3 tune2fs 1.41.12 (17-May-2010) Filesystem volume name: <none> Last mounted on: <not available> Filesystem UUID: 4cf3f507-e7b4-463c-be11-5b408097099b Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 19968 Block count: 19830 Reserved block count: 991 Free blocks: 18720 Free inodes: 19957 First block: 0 Block size: 65536 Fragment size: 65536 Blocks per group: 65528 Fragments per group: 65528 Inodes per group: 19968 Inode blocks per group: 78 Flex block group size: 16 Filesystem created: Sat Feb 5 14:39:55 2011 Last mount time: n/a Last write time: Sat Feb 5 14:40:02 2011 Mount count: 0 Maximum mount count: 37 Last checked: Sat Feb 5 14:39:55 2011 Check interval: 15552000 (6 months) Next check after: Thu Aug 4 14:39:55 2011 Lifetime writes: 70 MB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 Default directory hash: half_md4 Directory Hash Seed: afb5b570-9d47-4786-bad2-4aacb3b73516 Journal backup: inode blocks root@ubuntu:~# mount -t ext4 /dev/sda3 /mnt/ mount: wrong fs type, bad option, bad superblock on /dev/sda3, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so

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  • Why does Scala apply thunks automatically, sometimes?

    - by Anonymouse
    At just after 2:40 in ShadowofCatron's Scala Tutorial 3 video, it's pointed out that the parentheses following the name of a thunk are optional. "Buh?" said my functional programming brain, since the value of a function and the value it evaluates to when applied are completely different things. So I wrote the following to try this out. My thought process is described in the comments. object Main { var counter: Int = 10 def f(): Int = { counter = counter + 1; counter } def runThunk(t: () => Int): Int = { t() } def main(args: Array[String]): Unit = { val a = f() // I expect this to mean "apply f to no args" println(a) // and apparently it does val b = f // I expect this to mean "the value f", a function value println(b) // but it's the value it evaluates to when applied to no args println(b) // and the evaluation happens immediately, not in the call runThunk(b) // This is an error: it's not println doing something funny runThunk(f) // Not an error: seems to be val doing something funny } }   To be clear about the problem, this Scheme program (and the console dump which follows) shows what I expected the Scala program to do. (define counter (list 10)) (define f (lambda () (set-car! counter (+ (car counter) 1)) (car counter))) (define runThunk (lambda (t) (t))) (define main (lambda args (let ((a (f)) (b f)) (display a) (newline) (display b) (newline) (display b) (newline) (runThunk b) (runThunk f)))) > (main) 11 #<procedure:f> #<procedure:f> 13   After coming to this site to ask about this, I came across this answer which told me how to fix the above Scala program: val b = f _ // Hey Scala, I mean f, not f() But the underscore 'hint' is only needed sometimes. When I call runThunk(f), no hint is required. But when I 'alias' f to b with a val then apply it, it doesn't work: the evaluation happens in the val; and even lazy val works this way, so it's not the point of evaluation causing this behaviour.   That all leaves me with the question: Why does Scala sometimes automatically apply thunks when evaluating them? Is it, as I suspect, type inference? And if so, shouldn't a type system stay out of the language's semantics? Is this a good idea? Do Scala programmers apply thunks rather than refer to their values so much more often that making the parens optional is better overall? Examples written using Scala 2.8.0RC3, DrScheme 4.0.1 in R5RS.

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