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• Receive messages for derived types in MVVMLight

  - by Hrvoje

  Shouldn't this test pass: [TestMethod] public void derived_message_subscription() { bool handled = false; Messenger.Default.Register<GenericMessage<baseClass>>(this, true, (msg) => handled = true); Messenger.Default.Send(new GenericMessage<testClass>(new testClass())); Assert.IsTrue(handled); } public abstract class baseClass { } public class testClass : baseClass { } I have to receive all messages for classes that inherits from one base class. MVVMLight has bool property receiveDerivedMessagesToo in Register method, but it seems to me that it isn't working.

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• Does AsEnumerable() cache all result (LINQ)

  - by Akshay

  When we call a query operator on a sequence, a sequence-specific operator gets called. I mean if i call Where<>() operator on IEnumerable<>, the operator that will be called will be defined in Enumerable class and if it's called on IQueryable<>, the one defined in Queryable class will be called. Consider the operator Reverse, defined in the Enumerable class. If i want to call it on Iqueryable<> then I must use the AsEnumerable<>() operator to first convert it into IEnumerable<>. db.Countries.OrderBy(cntry=>cntry.CountryName).AsEnumerable().Reverse() But the Reverse operator got to have all records at the same time so that it can reverse them. In the above code do all the records get loaded in memory first and then the Reverse() operator is reversing it ?

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• DJANGO complex modelling

  - by SledgehammerPL

  Hello. I have such model now: receipt contains components. component contain product. The difference between component and product is, that component has quantity and measure unit: eg. component is 100g sugar - sugar is a product. So I need to make lots of components to satisfy different recipes - 100g sugar is not equal 200g sugar I wonder if I can remodel it to kick off components - in pure sql it's rather easy, but I'm trying to USE django - not making workarounds. class Receipt(models.Model): name = models.CharField(max_length=128) (...) components = models.ManyToManyField(Component) class Component(models.Model): quantity = models.FloatField(max_length=9) unit = models.ForeignKey(Unit) product = models.ForeignKey(Product) class Product(models.Model): name = models.CharField(max_length = 128) TIA

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• runtime/compile time polymorphism

  - by dmadhavaraj

  Hi , In the below code , why b1.subtract() fails . Please explain me the reason ie., what happens in JVM while invoking that method . class Base { public void add() { System.out.println("Base ADD"); } } class Child extends Base { public void add(){ System.out.println("Child ADD"); } public void subtract() { System.out.println("Child Subtract"); } } class MainClass { public static void main(String args[]) { Base b1 = new Base(); Base b2 = new Child(); Child b3 = new Child(); b1.add(); b1.subtract(); // ?????????** b2.add(); b3.subtract(); } }

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• What Can A 'TreeDict' (Or Treemap) Be Used For In Practice?

  - by Seun Osewa

  I'm developing a 'TreeDict' class in Python. This is a basically a dict that allows you to retrieve its key-value pairs in sorted order, just like the Treemap collection class in Java. I've implemented some functionality based on the way unique indexes in relational databases can be used, e.g. functions to let you retrieve values corresponding to a range of keys, keys greater than, less than or equal to a particular value in sorted order, strings or tuples that have a specific prefix in sorted order, etc. Unfortunately, I can't think of any real life problem that will require a class like this. I suspect that the reason we don't have sorted dicts in Python is that in practice they aren't required often enough to be worth it, but I want to be proved wrong. Can you think of any specific applications of a 'TreeDict'? Any real life problem that would be best solved by this data structure? I just want to know for sure whether this is worth it.

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• how to use multiple $_name using extends Zend_Db_Table_Abstract in zend frame work.

  - by karthik

  we tried to give our tables(users,messages) like this in two different abstract classes but it is not working. This is included in a file childconnect1.php ,is there any relation between the file name(childconnect1.php) and the class(Application_Model_childconnect1). class Application_Model_childconnect1 extends Zend_Db_Table_Abstract { protected $_name = 'users'; public function loginvalidation($username,$pwd) { $row = $this->fetchRow('UserName = \'' . $username . '\'and UserPW = \''. $pwd . '\''); if (!$row) { $msg="invalid"; return $msg; } else { return $row->toArray(); } } } class Application_Model_childconnect2 extends Zend_Db_Table_Abstract { protected $_name = 'messages'; public function replymessage($message) { $data=array( 'MessageText'=>$message ); $this->insert($data); } }

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• Push html attribute to array onClick

  - by Hunkeone

  I'm trying to push number attribute of the element to the array onclick with a simple function, but array contains only empty values separated with commas. Here's html code. <button type="button" class="btn btn-success btn-lg" number="12" onclick="basket.push(this.number)">toBakset</button> <button type="button" class="btn btn-success btn-lg" number="15" onclick="basket.push(this.number)">toBakset</button> <button type="button" class="btn btn-success btn-lg" number="18" onclick="basket.push(this.number)">toBakset</button> from the start "basket" array is empty. Seems this question is so dumb but I can't find a solution :(

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• Grails: Duplicates & unique constraint validation

  - by rukoche

  OK here is stripped down version of what I have in my app Artist domain: class Artist { String name Date lastMined def artistService static transients = ['artistService'] static hasMany = [events: Event] static constraints = { name(unique: true) lastMined(nullable: true) } def mine() { artistService.mine(this) } } Event domain: class Event { String name String details String country String town String place String url String date static belongsTo = [Artist] static hasMany = [artists: Artist] static constraints = { name(unique: true) url(unique: true) } } ArtistService: class ArtistService { def results = [ [ name:"name", details:"details", country:"country", town:"town", place:"place", url:"url", date:"date" ] ] def mine(Artist artist) { results << results[0] // now we have a duplicate results.each { def event = new Event(it) if (event.validate()) { if (artist.events.find{ it.name == event.name }) { log.info "grrr! valid duplicate name: ${event.name}" } artist.addToEvents(event) } } artist.lastMined = new Date() if (artist.events) { artist.save(flush: true) } } } In theory event.validate() should return false and event will not be added to artist, but it doesn't.. which results in DB exception on artist.save() Although I noticed that if duplicate event is persisted first everything works as intended. Is it bug or feature? :P

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• jsp update request happens to be invoked by a link

  - by Akshatha

  <tr class="bg-row1"> <td class="td-highlighted-2"> <div align="left"><a href="<%=contextPath%>/jsp/admin/UpdateProject.jsp"><%=searchList1.getProjid()%></a></div> </td> <td class="td-highlighted-2"> <div align="left"><%=searchList1.getProjname()%></div> </td> </tr> here jsp update request happens to be invoked by a link in updateproject.jsp how can i refer projid and projname value in a text box

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• Buffering db inserts in multithreaded program

  - by Winter

  I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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• Custom Sorting (IComparer on three fields)

  - by Kave

  I have a person class with three fields, Title, Name, Gender and I would like to create a Custom Sort for it to sort it first by Title, then by Name and then by Gender ascending: public class SortPerson : IComparer { public int Compare(object x, object y) { (…) } } I know how to do this for only one variable to compare against: But How would I have to proceed with three? public class SortPerson : IComparer { int IComparer.Compare(object a, object b) { Person p1=(Person)a; Person p2=(Person)b; if (p1.Title > p2.Title) return 1; if (p1.Title < p2.Title) return -1; else return 0; } } Many Thanks,

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• When is it safe to do a Response.Redirect() without throwing an exception?

  - by DDechant

  I have an intermediary class extending System.Web.UI.Page for all of my pages that require authentication. The class mostly does custom authentication handling. When a user with insufficient access attempts to visit a page, I try to redirect the user back to the login page while preventing any further page events from being executed (ie. Page_load). The first solution that came to mind was the default implementation of Response.Redirect. Of course the downside to this is the possibility of ThreadAbortExceptions being thrown. So my question is this: When (if at all) during the page life cycle is it actually safe to execute Response.Redirect() without ThreadAbortException ever being thrown? public class CustomPage : System.Web.UI.Page { protected override void OnInit(EventArgs e) { base.OnInit(e); if (!IsValid()) Response.Redirect("login.aspx", true); } }

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• How to persist and load an object which conforms to NSCoding protocol?

  - by mystify

  I have made an class which conforms to the NSCoding protocol and does all the encode and decode stuff. For my app, I simply want to persist an object from that class to the device and the next time when the app launches, I want to load that object back into memory. Basically it's just an class which holds some user input information. For example the user starts writing a text but then quits the app. Next time I want to load that data object. I guess I need NSKeyedArchiver? Is there a good tutorial on this? How do I do that?

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• CSS Selector Issue

  - by YsoL8

  Hello html body .home blog logged-in div #wrapper div #page div .cats I have a problem with selecting unordered lists (i.e ul li.class-name class-name-number) at the above dom location in CSS. I am working with a wordpress theme. Basically could I have suggestions for the correct selector to use in order to influence this tag? I can provide a simplified html structure if it will help. I've tried a number of selectors along the lines of: (sometimes)#page (# or .)cats (sometimes)ul li(sometimes with class name) EDIT: I've tried the selectors suggested in the wordpress docs. Thanks!

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• bulk update/delete entities of different kind in db.run_in_transaction

  - by Ray Yun

  Here goes pseudo code of bulk update/delete entities of different kind in single transaction. Note that Album and Song entities have AlbumGroup as root entity. class AlbumGroup: pass class Album: group = db.ReferenceProperty(reference_class=AlbumGroup,collection_name="albums") class Song: album = db.ReferenceProperty(reference_class=Album,collection_name="songs") def bulk_update_album_group(album_group): updated = [album_group] deleted = [] for album in album_group.albums: updated.append(album) for song in album.songs: if song.is_updated: updated.append(song) if song.is_deleted: deleted.append(song) db.put(updated) db.delete(deleted) a = AlbumGroup.all().filter("...").get() # bulk update/delete album group. for simplicity, album cannot be deleted. db.run_in_transaction(bulk_update_album_group,a) But I met a famous "Only Ancestor Queries in Transactions" error at the iterating reference properties like album.songs or album_group.albums. I guess ancestor() filter does not help because those entities are modified in memory. Should I not to iterate reference property in transaction function and always provide them as function parameters like def bulk_update_album_group(updated,deleted): ??? Is there any good coding pattern for this situation?

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• Generics and reflection in Java

  - by Ragesh

  This is probably a very basic question, but I'm really new to generics in Java and I'm having a hard time altering my thought process from the way things are done in C#, so bear with me. I'm trying to build a generic repository in Java. I've created an IRepository interface that looks like this: public interface IRepository<T extends IEntity> And a Repository class that looks like this: public class Repository<T extends IEntity> implements IRepository<T> Now, from within the constructor of my Repository class, I'd like to be able to "divine" the exact type of T. For example, if I instantiated a repository like this: IRepository<MyClass> repo = new Repository<MyClass>(); I'd like to know that T is actually MyClass. This is trivial in C#, but obviously generics are a totally different beast in Java and I can't seem to find anything that would help me do this.

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• How to have NHibernate persist a String.Empty property value as NULL

  - by Todd

  I have a fairly simple class that I want to save to SQL Server via NHibernate (w/ Fluent mappings). The class is made up mostly of optional string fields. My problem is I default the class fields to string.empty to avoid NullRefExceptions and when NHibernate saves the row to the database each column contains an empty string instead of null. Question: Is there a way for me to get NHibernate to automatically save null when the string property is an empty string? Or do I need to litter my code with if (string.empty) checks?

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• [PHP] Processing custom XML namespace within XSL

  - by sander

  I'm using the php class XSLTProcessor to generate HTML from a xsl. Within the xsl, I'd like all my custom namespace elements to be processed by my own processor class. So for example: <xsl:for-each select="doc/elements/*"> <doc:renderElement element="." /> </xsl:for-each> This should call the method renderElement of an instance of my custom processor class. I know I can enable calling php functions by using the registerPHPFunctions function. However, this only seems to support calling static methods.

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• Exception and Inheritance in JAVA

  - by user1759950

  Suppose we have this problem public class Father{ public void method1(){...} } public class Child1 extends Father{ public void method1() throws Exception{ super.method1(); ... } } Child1 extends Father and override method1 but given implementation Child1.method1 now throws a exception, this wont compile as override method can't throw new exceptions. What is the best solution? Propagate the required exception to the Father.. to me this is against encapsulation, inheritance and general OOP ( the father potentially throw and exception that will never happen ) Use a RuntimeException instead? This solution wont propagate the Exception to the father but I read In Oracle docs and others sources states class of exceptions should be used when "Client code cannot do anything" this is not that case, this exception will b useful to recover blablabla ( why is wrong to use RuntimeException instead? ) Other.. thanks, Federico

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• Ajax response is taking time to populate.

  - by Rachel

  I am having an util class which is not owned by me. I am calling one of the method of that util class which inturn calls one ajax function. And gives me response back. I need to make a decision depending on the response object. The problem is that response object takes some time to populate(mili seconds). var selector = dojo.byId("SelectorId"); var theChart = new chart( selector, 135, 92, style, frequency, time); if(theChart.data ===null){ console.log("No response"); }else{ Console.log("Use response data"); } and chart( selector, 135, 92, style, frequency, time); is not owned by me. chart() is from util class. above snippet works fine with break point. But when I remove the breakpoint it starts going in "if" block always. Hows can I solve this issue.

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• What is the use of reflection in Java/C# etc

  - by zengr

  I was just curious, why should we use reflection in the first place? // Without reflection Foo foo = new Foo(); foo.hello(); // With reflection Class cls = Class.forName("Foo"); Object foo = cls.newInstance(); Method method = cls.getMethod("hello", null); method.invoke(foo, null); We can simply create an object and call the class's method, but why do the same using forName, newInstance and getMthod functions? To make everything dynamic?

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• Fastest/One-liner way to list attr_accessors in Ruby?

  - by viatropos

  What's the shortest, one-liner way to list all methods defined with attr_accessor? I would like to make it so, if I have a class MyBaseClass, anything that extends that, I can get the attr_accessor's defined in the subclasses. Something like this: class MyBaseClass < Hash def attributes # ?? end end class SubClass < MyBaseClass attr_accessor :id, :title, :body end puts SubClass.new.attributes.inspect #=> [id, title, body] What about to display just the attr_reader and attr_writer definitions?

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• Check if a variable is empty

  - by Thomas

  I have some user-submitted variables that I want to display in a different part of my site like this: <div class="pre_box">Term: </div> <div class="entry"><?php $key='term'; echo get_post_meta($post->ID, $key, true); ?></div> Occasionally, these variables might be empty in which case I don't want to display the label for the empty variable. In the example above I would want to hide the <div class="pre_box">Term: </div> part. Is there some simple way to check if a php variable like the one above is empty and prevent the label from being displayed?

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• IRepository with Inherited Classes

  - by Stacey

  In keeping with the Repository pattern of data input, I've a question in regards to using inherited classes. For instance, suppose I would have the class... class Employee IEmployeeRepository { Add(Employee employee); } This works fine, nothing wrong with it so far... but now let's say I continue on.. class Manager : Employee Okay, now let's assume that I never need to enter a manager different than an Employee? What's the best approach here? Would a scenario such as .. IEmployeeRepository { Add<T>(T employee) where T : Employee } Be the best approach, or do I need to abstract a different repository for each type?

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• has_many relation doesn't seems right or logical, some thing like belongs_to_many looks right

  - by Vijendra

  My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below. class Company has_many :employments has_many :users, :through = :employments end class Employment belongs_to :company belongs_to :user end class User has_many :employments has_many :companies, :through = :employments #This doesn't looks correct end User has many companies doesn't looks logically meaningful.It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many? But that also will gives the same meaning. Can some one please suggest the right way for representing these relationships?

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