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• SQL Get Latest Unique Rows

  - by Simpleton

  I have a log table, each row representing an object logging its state. Each object has a unique, unchanging GUID. There are multiple objects logging their states, so there will be thousands of entries, with objects continually inserting new logs. Everytime an object checks in, it is via an INSERT. I have the PrimaryKey, GUID, ObjectState, and LogDate columns in tblObjects. I want to select the latest (by datetime) log entry for each unique GUID from tblObjects, in effect a 'snapshot' of all the objects. How can this be accomplished?

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• Get unique artist names from MPMediaQuery

  - by Akash Malhotra

  I am using MPMediaQuery to get all artists from library. Its returning unique names I guess but the problem is I have artists in my library like "Alice In Chains" and "Alice In Chains ". The second "Alice In Chains" has some white spaces at the end, so it returns both. I dont want that. Heres the code... MPMediaQuery *query=[MPMediaQuery artistsQuery]; NSArray *artists=[query collections]; artistNames=[[NSMutableArray alloc]init]; for(MPMediaItemCollection *collection in artists) { MPMediaItem *item=[collection representativeItem]; [artistNames addObject:[item valueForProperty:MPMediaItemPropertyArtist]]; } uniqueNames=[[NSMutableArray alloc]init]; for(id object in artistNames) { if(![uniqueNames containsObject:object]) { [uniqueNames addObject:object]; } } Any ideas?

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• Obtaining reference to Class instance by string name - VB.NET

  - by Jeff Williams

  Is it possible using Reflection or some other method to obtain a reference to a specific class instance from the name of that class instance? For example the framework for the applications i develop heavily uses public class instances such as: Public bMyreference as MyReference = new MyReference Then throughout the application bMyReference is used by custom controls and code. One of the properties of the custom controls is the "FieldName" which references a Property in these class instances (bMyReference.MyField) as a string. What i would like to be able to do is analyze this string "bMyReference.MyField" and then refer back to the actual Instance/Property. In VB6 I would use an EVAL or something simular to convert the string to an actual object but this obviously doesn't work in VB.net What I'm picturing is something like this Dim FieldName as String = MyControl.FieldName ' sets FielName to bMyReference.MyField Dim FieldObject() as String = FieldName.Split(".") ' Split into the Object / Property Dim myInstance as Object = ......... ' Obtain a reference to the Instance and set as myInstance Dim myProperty = myInstance.GetType().GetProperty(FieldObject(1))

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• Passing a JavaScript variable to a helper method

  - by Brendan Vogt

  I am using ASP.NET MVC 3 and the YUI library. I created my own helper method to redirect to an edit view by passing in the item's ID from the Model as such: window.location = '@Url.RouteUrl(Url.NewsEdit(@Model.NewsId))'; Now I am busy populating my YUI data table and would like to call my helper method like above, not sure if it is possible because I get the item's ID by JavaScript like: var formatActionLinks = function (oCell, oRecord, oColumn, oData) { var newsId = oRecord.getData('NewsId'); oCell.innerHTML = '<a href="/News/Edit/' + newsId + '">Edit</a>'; };

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• Can anyone give me some information about crystalreport?

  - by hcemp

  One of my projects needs to use crystalreport,so i want some information about it. ps:push model

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• Cocoa : Remove Item from NSArrayController

  - by Holli

  I have a NSArrayController bound to a NSTableView. With this I have the typical Add/Remove buttons. While Adding an item is very straight forward (I call a method, create an object with default values and add it) I have problems deleting objects from the controller. I know I can do this the easy way when connecting the button with the remove action from the ArrayController. But this is not what I want. I need to remove the object manually because I have some additional code to process. Anway, removing objects seems far more complcated then I expected. It already tried: NSArray *items = [doToItemsArrayController selectedObjects]; [doToItemsArrayController removeSelectedObjects:items]; or NSIndexSet *iSet = [doToItemsArrayController selectionIndexes]; [doToItemsArrayController removeSelectionIndexes:iSet]; None of them seems to work. How do I remove the selected Object from an NSArrayController with Objective-C code?

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• Reading int from a hidden field in .aspx

  - by vikp

  Hi, I'm struggling to read an int from the hidden field on aspx page. <input type = "hidden" id = "myIntegerId" name = "integerId" value= "<%: Model.MyObjectId %>" runat = "server" /> The value is definately on the form, I can see it in the debugger and print it with <%: % When I read the form values in the controller, instead of an int I recieve a following string: <%: Model.MyObjectId % I have tried casting data in the hidden field to string and calling ToString() method on that field, neither has worked. The data is submitted using the post event. I have a feeling that I'm missing something very basic... Any help is greately appreciated. Thanks

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• Should I use Enumeration or Class stereotype in UML to represent a type directory table?

  - by Ivan

  Let's take 2 UML class model entities: One represents an actual Order and another represents an Orede Type. Any Order corresponds to one Type. A 2-way-naviglabe many Orders to one Type relation is meant. Order Type instances are, for example, "Request availability", "Request price", "Preorder", "Buy", "Cancel", "Request support", etc. Order Types are to be addable and editable in the resulting application. Should I model Order Type as Class or as Enumeration? From the data perspective I can't see the difference actually.

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• Communication between (Desktop/Smartphone) Application and Web Application

  - by erlord

  Hi all I wonder what is the commonly used method and protocol for a, say, smartphone application to send its data to a web application (where these data should be proceeded and stored). My naive beginner's approach would be something like this: From my smartphone app, use a framework encoding my data object into a json object Send this object via http to a listener addressed by a dedicated URL On the server side, use a JSON parser and store it via ORM etc. into a database Questions: Is this too naive? 2a. If yes: What is the appropiate way to tackle this workflow? 2b. If no: What frameworks to use in JAVA for serializing/deserializing to/from JSON objects? Any example for a json listener in the web? Tutorial for a http-protocol based Java listener? Thanks for all answers and suggestions in advance. Regs Me

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• ProgrammingError: (1146, "Table 'test_<DB>.<TABLE>' doesn't exist") when running unit test for Djang

  - by abigblackman

  I'm running a unit test using the Django framework and get this error. Running the actual code does not have this problem, running the unit tests creates a test database on the fly so I suspect the issue lies there. The code that throws the error looks like this member = Member.objects.get(email=email_address) and the model looks like class Member(models.Model): member_id = models.IntegerField(primary_key=True) created_on = models.DateTimeField(editable=False, default=datetime.datetime.utcnow()) flags = models.IntegerField(default=0) email = models.CharField(max_length=150, blank=True) phone = models.CharField(max_length=150, blank=True) country_iso = models.CharField(max_length=6, blank=True) location_id = models.IntegerField(null=True, blank=True) facebook_uid = models.IntegerField(null=True, blank=True) utc_offset = models.IntegerField(null=True, blank=True) tokens = models.CharField(max_length=3000, blank=True) class Meta: db_table = u'member' there's nothing too odd there i can see. the user running the tests has the same permissions to the database server as the user that runs the website where else can I look to see what's going wrong, why is this table not being created?

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• Django many-to-many relationship to self with extra data, how do I select from a certain direction?

  - by Jake

  I have some hierarchical data where each Set can have many members and can belong to more than one Set(group) Here are the models: class Set(models.Model): ... groups = models.ManyToManyField('self', through='Membership', symmetrical=False) members = models.ManyToManyField('self', through='Membership', symmetrical=False) class Membership(models.Model): group = models.ForeignKey( Set, related_name='Members' ) member = models.ForeignKey( Set, related_name='Groups' ) order = models.IntegerField( default=-1 ) I want to know how to get all the members or all the groups for a Set instance. I think I can do it as follows, but it's not very logical, can anyone tell me what's going on and how I should be doing it? # This gives me a set of Sets # Which seems to be the groups this Set belongs to set_instance.set_set.all() # These give me a set of Memberships, not Sets set_instance.Members.all() set_instance.Groups.all() # These they both return a set of Sets # which seem to be the members of this one set_instance.members.all() set_instance.groups.all()

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• Data scheme question

  - by Matt

  I am designing a data model for a local city page, more like requirements for it. So 4 tables: Country, State, City, neighbourhood. Real life relationships is: Country owns multiple State which owns multiple cities which ows multiple neighbourhoods. In the data model: Do we link these with FK the same way or link each with each? Like in each table there will even be a Country ID, State ID, CityID and NeighbourhoodID so each connected with each? Other wise to reach neighbourhood from country we need to join 2 other tables in between? There are more tables I need to maintain for IP addess of cities, latitude/longitude, etc.

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• String intern puzzles

  - by Yob

  On this blog I found interesting String puzzles: --- Quote --- String te = "te", st = "st"; //"test".length(); String username = te + st; username.intern(); System.out.println("String object the same is: " + (username == "test")); prints String object the same is: true but uncomment the "test".length(); line and it prints String object the same is: false --- EoQ --- Being honest I don't understand why the outputs are different. Could you please explain me what's the cause of such behaviour?

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• EF 4.x generated entity classes (POCO) and Map files

  - by JBeckton

  I have an MVC 4 app that I am working on and using the code first implementation except I cheated a bit and created my database first then generated my entity classes (poco) from my database using the EF power tools (reverse engineer). I guess you can say I did database first method but I have no edmx file just the context class and my entity classes (poco) I have a few projects in the works using MVC and EF with pocos but just the one project I used the tool to generate my pocos from the database. My question is about the mapping files that get created when I generate my pocos using the tool. What is the purpose of these Map files? I figured the map files are needed when generating the db from the model like with the true code first method, in my case where I am using a tool to generate my model from the database do the map files have any influence on how my app uses the entity classes?

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• Using ASP.NET Session for Lifetime Management (Unity)

  - by Sigray

  I am considering using Unity to manage the lifetime of a custom user class instance. I am planning on extending the LifetimeManager with a custom ASP.NET session manager. What I want to be able to do is store and retrieve the currently logged in user object from my custom classes, and have Unity get the instance of User from the session object in ASP.NET, or (when in a Win32 project) retrieve it statically or from the current thread. So far my best solution is to create a static instance of my Unity container on startup, and use the Resolve method to get my User object from each of my classes. However, this seems to create a dependency on the unity container in my other classes. What is the more "Unity" way of accomplishing this goal? I would like to be able to read/replace the current User instance from any class.

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• RIA Services - Two entity models share an entity name

  - by Alex

  I have two entity models hooked up to two different databases. However, the two databases both have a table named 'brand', for example. As such, there is a naming conflict in my models. Now, I've been able to add a namespace to each model, via Custom Tool Namespace in the model's properties, but the generated code in my Silverlight project will try to use both namespaces, and come up with this, Imports MyProject.ModelA Imports MyProject.ModelB Public ReadOnly Property brands() As EntitySet(Of brand) Get Return MyBase.EntityContainer.GetEntitySet(Of brand) End Get End Property giving me this exception: 'Error 1 'brand' is ambiguous, imported from the namespaces or types 'MyProject.ModelA,MyProject.ModelB'. Has anyone had experience with naming conflicts like this using RIA services? How did you solve it?

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• [Cocoa] Temporarily disabled NSArrayController filterPredicate, or consult ManagedObjectContext?

  - by ndg

  I have an NSArrayController which is bound to a class in my Managed Object Context. During runtime the NSArrayController can have a number of different filter predicates applied. At certain intervals, I want to iterate through my NSArrayController's contents regardless of the filter predicate applied to it. To do this, I set the filterPredicate to nil and then reinstate it after having iterated through my array. This seems to work, but I'm wondering if it's best practice? Should I instead be polling my Managed Object Context manually? NSPredicate *predicate = nil; predicate = [myArrayController filterPredicate]; [myArrayController setFilterPredicate:nil]; for(MyManagedObject *object in [myArrayController arrangedObjects]) { // ... } [myArrayController setFilterPredicate:predicate];

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• Django: way to test what class a generic relation content_object is?

  - by bitbutter

  In my project I have a class, NewsItem. Instances of NewsItem act like a wrapper. They can be associated with either an ArtWork instance, or an Announcement instance. Here's how the NewsItem model looks: class NewsItem(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') date = models.DateTimeField(default=datetime.datetime.now,) class Meta: ordering = ('-date',) def __unicode__(self): return (self.title()) In a template I'm dealing with a NewsItem instance, and would like to output a certain bunch of html it it's 'wrapping' an Artwork instance, and a different bunch of html if it's wrapping an Announcement instance. Could someone explain how I can write a conditional to test for this? My first naive try looked like this: {% if news_item.content_object.type=='Artwork' %}do this{% else %}do that{% endif %}

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• Testing a (big) collection retrieved from a db

  - by Bas

  I'm currently doing integration testing on a live database and I have the following sql statement: var date = DateTime.Parse("01-01-2010 20:30:00"); var result = datacontext.Repository<IObject>().Where(r => r.DateTime > date).First(); Assert.IsFalse(result.Finished); I need to test if the results retrieved from the statement, where the given date is less then the date of the object, have Finished set to False. I do not know how many results I get back and currently I'm getting the first object of the list and check if that object has Finished set to false. I know testing only the first item of the list is not valid testing, as a solution for that I could iterate through the list and check all items on Finished, but putting logic in a Test is kinda going against the concept of writing 'good' tests. So my question is: Does anyone have a good solution of how to properly test the results of this list?

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• tricky SQL when joining

  - by Erik

  I've two tables, shows and objects. I want to print out the latest objects, and the shownames for them. Right now I'm doing it this way: SELECT MAX(objects.id) as max_id, shows.name, shows.id FROM shows, objects WHERE shows.id = objects.showId GROUP BY shows.name however, if I also want to fetch the episode of the object I can't put it like SELECT object.episode [...], because then wont automatically select the object which is MAX(objects.id), so my question is how to do that? If you haven't already figured out my tables they're like this: Shows id name and also: Objects id name episode season showId Using MySQL. Thanks!

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• Delphi constants and references

  - by Sambatyon

  I want to pass constant references to functions in delphi, so I am sure that the referenced object won't change and to save time and memory. So I want to declare a function like function foo(var const Value : Bar) : Boolean; however this is not allowed. I thought constant values would be automatically sent as references. However I found out that it is not the case (getting the address of an object before sending it to the function gives me $12F50C and the address of the same object inside the function is $12F564) What can I do to send constant references?

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• MVVM where does the code to load the data belong?

  - by cody

  As I wrap my head around the mvvm thing, the view is the view, and the viewmodel is 'a modal of a view' and the model are the entities we are dealing with (or at least that is my understanding). But I'm unclear as to what and when the model entities are populated. So for example: Lets say I have app that needs to create a new record in a DB. And that record should have default values to start with. Who is responsible for the new record, and getting the default values. Does this have anything to do with MVVM or is that part of a data access layer? Who calls the the viewmodel? Or for existing records when\where are the records retrieved? And saved if altered? Thanks

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• Form Inheritance in Visual Studios designer implementations

  - by CooPzZ

  I'm in the process of Moving a project from Visual Studio 2003 to 2005 and have just seen the The event Click is read-only and cannot be changed when using inherited forms regardless of the Modifier on the Base Forms Controls will make all the Controls from the Base Readonly in the designer (Though in 2003 it didn't work this way). I found this post metioning that this functionality has been temporarily" disabled http://social.msdn.microsoft.com/Forums/en-US/winformsdesigner/thread/c25cec28-67a5-4e30-bb2d-9f8dbd41eb3a Can anyone confirm whether this feature is used anymore? or how to program around it to be able to use the Base Control Events and still have a designer? This is one way I've found but quite painfull when it used to do the plumbing for you. even just hiding one of the controls you have manually do now. Public Class BFormChild Friend Overrides Sub cmdApply_Click(ByVal sender As Object, ByVal e As System.EventArgs) MyBase.cmdApply_Click(sender, e) End Sub Friend Overrides Sub cmdCancel_Click(ByVal sender As Object, ByVal e As System.EventArgs) MyBase.cmdCancel_Click(sender, e) End Sub Friend Overrides Sub cmdOk_Click(ByVal sender As Object, ByVal e As System.EventArgs) MyBase.cmdOk_Click(sender, e) End Sub End Class

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• How to handle failure to release a resource which is contained in a smart pointer?

  - by cj

  How should an error during resource deallocation be handled, when the object representing the resource is contained in a shared pointer? Smart pointers are a useful tool to manage resources safely. Examples of such resources are memory, disk files, database connections, or network connections. // open a connection to the local HTTP port boost::shared_ptr<Socket> socket = Socket::connect("localhost:80"); In a typical scenario, the class encapsulating the resource should be noncopyable and polymorphic. A good way to support this is to provide a factory method returning a shared pointer, and declare all constructors non-public. The shared pointers can now be copied from and assigned to freely. The object is automatically destroyed when no reference to it remains, and the destructor then releases the resource. /** A TCP/IP connection. */ class Socket { public: static boost::shared_ptr<Socket> connect(const std::string& address); virtual ~Socket(); protected: Socket(const std::string& address); private: // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; But there is a problem with this approach. The destructor must not throw, so a failure to release the resource will remain undetected. A common way out of this problem is to add a public method to release the resource. class Socket { public: virtual void close(); // may throw // ... }; Unfortunately, this approach introduces another problem: Our objects may now contain resources which have already been released. This complicates the implementation of the resource class. Even worse, it makes it possible for clients of the class to use it incorrectly. The following example may seem far-fetched, but it is a common pitfall in multi-threaded code. socket->close(); // ... size_t nread = socket->read(&buffer[0], buffer.size()); // wrong use! Either we ensure that the resource is not released before the object is destroyed, thereby losing any way to deal with a failed resource deallocation. Or we provide a way to release the resource explicitly during the object's lifetime, thereby making it possible to use the resource class incorrectly. There is a way out of this dilemma. But the solution involves using a modified shared pointer class. These modifications are likely to be controversial. Typical shared pointer implementations, such as boost::shared_ptr, require that no exception be thrown when their object's destructor is called. Generally, no destructor should ever throw, so this is a reasonable requirement. These implementations also allow a custom deleter function to be specified, which is called in lieu of the destructor when no reference to the object remains. The no-throw requirement is extended to this custom deleter function. The rationale for this requirement is clear: The shared pointer's destructor must not throw. If the deleter function does not throw, nor will the shared pointer's destructor. However, the same holds for other member functions of the shared pointer which lead to resource deallocation, e.g. reset(): If resource deallocation fails, no exception can be thrown. The solution proposed here is to allow custom deleter functions to throw. This means that the modified shared pointer's destructor must catch exceptions thrown by the deleter function. On the other hand, member functions other than the destructor, e.g. reset(), shall not catch exceptions of the deleter function (and their implementation becomes somewhat more complicated). Here is the original example, using a throwing deleter function: /** A TCP/IP connection. */ class Socket { public: static SharedPtr<Socket> connect(const std::string& address); protected: Socket(const std::string& address); virtual Socket() { } private: struct Deleter; // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; struct Socket::Deleter { void operator()(Socket* socket) { // Close the connection. If an error occurs, delete the socket // and throw an exception. delete socket; } }; SharedPtr<Socket> Socket::connect(const std::string& address) { return SharedPtr<Socket>(new Socket(address), Deleter()); } We can now use reset() to free the resource explicitly. If there is still a reference to the resource in another thread or another part of the program, calling reset() will only decrement the reference count. If this is the last reference to the resource, the resource is released. If resource deallocation fails, an exception is thrown. SharedPtr<Socket> socket = Socket::connect("localhost:80"); // ... socket.reset();

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• Should I skip authorization, with CanCan, of an action that instantiates a resource?

  - by irkenInvader

  I am writing a web app to pick random lists of cards from larger, complete sets of cards. I have a Card model and a CardSet model. Both models have a full RESTful set of 7 actions (:index, :new, :show, etc). The CardSetsController has an extra action for creating random sets: :random. # app/models/card_set.rb class CardSet < ActiveRecord::Base belongs_to :creator, :class_name => "User" has_many :memberships has_many :cards, :through => :memberships # app/models/card.rb class Card < ActiveRecord::Base belongs_to :creator, :class_name => "User" has_many :memberships has_many :card_sets, :through => :memberships I have added Devise for authentication and CanCan for authorizations. I have users with an 'editor' role. Editors are allowed to create new CardSets. Guest users (Users who have not logged in) can only use the :index and :show actions. These authorizations are working as designed. Editors can currently use both the :random and the :new actions without any problems. Guest users, as expected, cannot. # app/controllers/card_sets_controller.rb class CardSetsController < ApplicationController before_filter :authenticate_user!, :except => [:show, :index] load_and_authorize_resource I want to allow guest users to use the :random action, but not the :new action. In other words, they can see new random sets, but not save them. The "Save" button on the :random action's view is hidden (as designed) from the guest users. The problem is, the first thing the :random action does is build a new instance of the CardSet model to fill out the view. When cancan tries to load_and_authorize_resource a new CardSet, it throws a CanCan::AccessDenied exception. Therefore, the view never loads and the guest user is served a "You need to sign in or sign up before continuing" message. # app/controllers/card_sets_controllers.rb def random @card_set = CardSet.new( :name => "New Set of 10", :set_type => "Set of 10" ) I realize that I can tell load_and_authorize_resource to skip the :random action by passing :except => :random to the call, but that just feels "wrong" for some reason. What's the "right" way to do this? Should I create the new random set without instantiating a new CardSet? Should I go ahead and add the exception?

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