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  • Is writing a reference atomic on 64bit VMs

    - by Steffen Heil
    Hi The java memory model mandates that writing a int is atomic: That is, if you write a value to it (consisting of 4 bytes) in one thread and read it in another, you will get all bytes or none, but never 2 new bytes and 2 old bytes or such. This is not guaranteed for long. Here, writing 0x1122334455667788 to a variable holding 0 before could result in another thread reading 0x112233440000000 or 0x0000000055667788. Now the specification does not mandate object references to be either int or long-sized. For type safety reasons I suspect they are guaranteed to be written atomiacally, but on a 64bit VM these references could be very well 64bit values (merely memory addresses). No here are my question: Are there any memory model specs covering this (that I haven't found)? Are long-writes suspect to be atomic on 64bit VMs? Are VMs forced to map references to 32bit? Regards, Steffen

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  • clear view of box model

    - by Abhimanyu
    As far as i know every element in HTML associated with padding(left, right, top, bottom) , margin(left, right, top, bottom) which will create the box model for that so that we can figure it out its actual position with respect to document. any idea over it?

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  • Codeigniter Best Practices for Model functions

    - by user270797
    Say my application has a "Posts" model, and one of the function is add_post(), it might be something like: function add_post($data) { $this-db-insert('posts',$data); } Where $data is an array: $data = array ('datetime'='2010-10-10 01:11:11', 'title'='test','body'='testing'); Is this best practice? It means if you use that function you need to know the names of the database fields where as my understanding of OOP is that you shouldnt need to know how the method works etc etc

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  • Odd ActiveRecord model dynamic initialization bug in production

    - by qfinder
    I've got an ActiveRecord (2.3.5) model that occasionally exhibits incorrect behavior that appears to be related to a problem in its dynamic initialization. Here's the code: class Widget < ActiveRecord::Base extend ActiveSupport::Memoizable serialize :settings VALID_SETTINGS = %w(show_on_sale show_upcoming show_current show_past) VALID_SETTINGS.each do |setting| class_eval %{ def #{setting}=(val); self.settings[:#{setting}] = (val == "1"); end def #{setting}; self.settings[:#{setting}]; end } end def initialize_settings self.settings ||= { :show_on_sale => true, :show_upcoming => true } end after_initialize :initialize_settings # All the other stuff the model does end The idea was to use a single record field (settings) to persist a bunch of configuration data for this object, but allow all the settings to seamlessly work with form helpers and the like. (Why this approach makes sense here is a little out of scope, but let's assume that it does.) Net-net, Widget should end up with instance methods (eg #show_on_sale= #show_on_sale) for all the entires in the VALID_SETTINGS array. Any default values should be specified in initialize_settings. And indeed this works, mostly. In dev and staging, no problems at all. But in production, the app sometimes ends up in a state where a) any writes to the dynamically generated setters fail and b) none of the default values appear to be set - although my leading theory is that the dynamically generated reader methods are just broken. The code, db, and environment is otherwise identical between the three. A typical error message / backtrace on the fail looks like: IndexError: index 141145 out of string (eval):2:in []=' (eval):2:inshow_on_sale=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2746:in send' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2746:inattributes=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2742:in each' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2742:inattributes=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2634:in `update_attributes!' ...(then controller and all the way down) Ideas or theories as to what might be going on? My leading theory is that something is going wrong in instance initialization wherein the class instance variable settings is ending up as a string rather than a hash. This explains both the above setter failure (:show_on_sale is being used to index into the string) and the fact that getters don't work (an out of bounds [] call on a string just returns nil). But then how and why might settings occasionally end up as a string rather than hash?

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  • Creating a nested model form

    - by Elliot
    Hey Guys, I'm trying to build a multi model form - but one of the issues, is I need to link the models within the form. For example, lets say the form I have has the following models: Users, Profiles When creating a new user, I'd like to create a new profile simultaneously, and then link the two. The issue is, if neither have been created yet, they don't have ID's yet - so how can I assign linking values? Thanks! -Elliot

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  • Java Frameworks that support Entity-Attribute-Value Models

    - by jm04469
    I am interested in developing a portal-based application that works with EAV models and would like to know if there are any Java frameworks that aid in this type of development? salesforce.com uses EAV and currently has twenty tables. The framework I seek should allow it to be configurable to different EAV implementations

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  • Reporting Services 2005 Model using WCF Service for data

    - by Stu
    I am trying to use WCF Services as models for SQL Server Reporting Services 2005 reports. I can do this if I design the reports in the designer but cannot do it for a Reporting Model project which I think I need to make reports in the Report Builder. My full requirement is to have a report builder that the users can use building reports based on DTOs supplied from my WCF service. Thanks

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  • Java JList model

    - by Alaa
    How can I make a list model from a JList in order to be able to insert an item into it. I want to use this method: addElement(java.lang.Object item) I found an explanation here, but the problem is that ListModel is an interface and even if I write an implementation and override its method, I can't use the addElement() method

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  • Model Validation for record creation in rails

    - by Elliot
    Hey Guys, Lets say the model for books is: created_at user_id (int) author_id (int) genre_id (int) pages (int) I want to let people change the "created_at" field upon record creation. I also want to make sure that a record can't have the exact same created_at, user_id, and author_id as any other record (i.e. each needs its own date). Whats the best to perform this type of validation, and how should I go about doing it? Best, Elliot

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  • How to monkeypatch Issue model in Redmine from a plugin, specifically redmine_task_board

    - by armmer
    I'm trying to add a custom sort method to the Issue.rb model in Redmine from the redmine_task_board plugin. My commit on github I don't know if this is a lack of knowledge about Rails plugins on my part or something specific I have to do with Redmine. Redmine 0.8.6.stable I want this method so that when I show the Task Board show method from tasks_board_controller I can sort the tickets in each column by Issue.priority.position. Thank you for any help.

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  • Save simple data in Magento's DB w/o Model

    - by Joseph Mastey
    I'm looking to save some data in the Magento database without hassling with creating a new EAV object (or even a DB table if I can avoid it). Is there any place that you all know about that Magento will let you store serialized data? If it matters, the data is a serialized set of SKUs that I need to retrieve. I know that I could create a new model, or possibly even create an attribute as a flag on each product, but those are both really overkill for my purposes. Thanks, Joe

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  • WPF/MVVM: Delegating a domain Model collection to a ViewModel

    - by msfanboy
    A domain model collection (normally a List or IEnumerable) is delegated to a ViewModel. Thats means my CustomerViewModel has a order collection of type List or IEnumerable. No change in the list is recognized by the bound control. But with ObservableCollection it is. This is a problem in the MVVM design pattern. How do you cope with it?

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  • What situations does a Monostate pattern model?

    - by devoured elysium
    I know what both a Singleton or a Monostate are and how to implement them. Although I can see many uses for a Singleton, I can't imagine a situation where I would want to let the user create as many instances of my class although in reality only one really exists behind the scenes. Can anybody help me here? I know that for several reasons one should stay away from both patterns, but in theory, what kind of problems does the Monostate model? Thanks

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  • List of Django model instance foreign keys losing consistency during state changes.

    - by Joshua
    I have model, Match, with two foreign keys: class Match(model.Model): winner = models.ForeignKey(Player) loser = models.ForeignKey(Player) When I loop over Match I find that each model instance uses a unique object for the foreign key. This ends up biting me because it introduces inconsistency, here is an example: >>> def print_elo(match_list): ... for match in match_list: ... print match.winner.id, match.winner.elo ... print match.loser.id, match.loser.elo ... >>> print_elo(teacher_match_list) 4 1192.0000000000 2 1192.0000000000 5 1208.0000000000 2 1192.0000000000 5 1208.0000000000 4 1192.0000000000 >>> teacher_match_list[0].winner.elo = 3000 >>> print_elo(teacher_match_list) 4 3000 # Object 4 2 1192.0000000000 5 1208.0000000000 2 1192.0000000000 5 1208.0000000000 4 1192.0000000000 # Object 4 >>> I solved this problem like so: def unify_refrences(match_list): """Makes each unique refrence to a model instance non-unique. In cases where multiple model instances are being used django creates a new object for each model instance, even if it that means creating the same instance twice. If one of these objects has its state changed any other object refrencing the same model instance will not be updated. This method ensure that state changes are seen. It makes sure that variables which hold objects pointing to the same model all hold the same object. Visually this means that a list of [var1, var2] whose internals look like so: var1 --> object1 --> model1 var2 --> object2 --> model1 Will result in the internals being changed so that: var1 --> object1 --> model1 var2 ------^ """ match_dict = {} for match in match_list: try: match.winner = match_dict[match.winner.id] except KeyError: match_dict[match.winner.id] = match.winner try: match.loser = match_dict[match.loser.id] except KeyError: match_dict[match.loser.id] = match.loser My question: Is there a way to solve the problem more elegantly through the use of QuerySets without needing to call save at any point? If not, I'd like to make the solution more generic: how can you get a list of the foreign keys on a model instance or do you have a better generic solution to my problem? Please correct me if you think I don't understand why this is happening.

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  • Fluent: Table name different from entity name

    - by Matt
    I am trying to use the automapping feature of Fluent with nHinbernate to map a class with a different name than the table itself is name. (This is purely for stylistic reasons we have a class named Foo which contains an object named Bar but the table name is FooBar. We would rather not have a property Foo.FooBar.) I can't find anything detailing how to give Fluent a clue on this change.

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  • Removing associated entity JPA

    - by Marcel
    Hi I have a question regarding JPA persistence in Glassfish. Situation: I have a Supplier class that has a 1:n bidirectional relation to SupplierAddress. I would like to have the following behaviour: If I remove the SupplierAddress object from the List in the Supplier object and update it via the merge(supplierobject), the SupplierAddress tupel/object should be deleted. Is there an annotation do configure it like this or do I have to delete it manually. Any help would be very appreciated. Greetings Marcel

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  • How do I write this as an expression?

    - by itchi
    I'm trying to rewrite a linq to entities query to an expression. My model is a School can have many Persons where Persons are inherited out to teachers, students, etc. The following query works for me: IQueryable<DAL.TEACHER> teacher = from p in School select p.PERSON as ESBDAL.TEACHER; How would I write this as a query expression? I thought something like: IQueryable<DAL.TEACHER> teacher = School.Select(x=>x.PERSON) as IQueryable<DAL.TEACHER>; ...but it does not. Am I misunderstanding the .Select()?

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  • partial entity loading and management in silverlight / wcf ria

    - by Dan Wray
    I have a Silverlight 4 app which pulls entities down from a database using WCF RIA services. These data objects are fairly simple, just a few fields but one of those fields contains binary data of an arbitrarily size. The application needs access to this data basically asap after a user has logged in, to display in a list, enable selection etc. My problem is because of the size of this data, the load times are not acceptable and can approach the default timeout of the RIA service. I'd like to somehow partially load the objects into my local data context so that I have the IDs, names etc but not the binary data. I could then at a later point (ie when it's actually needed) populate the binary fields of those objects I need to display. Any suggestions on how to accomplish this would be welcome. Another approach which has occurred to me whilst writing this question (how often does that happen?!) is that I could move the binary data into a seperate database table joined to the original record 1:1 which would allow me to make use of RIA's lazy loading on that binary data. again.. comments welcome! Thanks.

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  • J2ME HTTPS Connection Problem: Certificate was issued by an unrecognized entity

    - by Mustafa
    I am developing a little J2ME application that will read our grades from our university's server. With Desktop Applications, It is fine, I can do it but in J2ME, it always gives me this error, even I use well-known services like HTTPS Google, I still get the same error. urlConn = (HttpsConnection) Connector.open("https://stars.bilkent.edu.tr/srs/ajax/login.php"); urlConn.setRequestMethod(HttpsConnection.POST); urlConn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); o = urlConn.openOutputStream(); // Sending my POST requests to server input = urlConn.openDataInputStream(); In the last line I always get the error I mentioned above. What should I do about it?

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  • How entity edit URL from within plug-in in MS Dyanmics CRM 4.0

    - by Greg McGuffey
    I would like to have a workflow create a task, then email the assigned user that they have a new task and include a link to the newly created task in the body of the email. I have client side code that will correctly create the edit URL, using the entities GUID and stores it in a custom attribute. However, when the task is created from within a workflow, the client script isn't run. So, I think a plug-in should work, but I can't figure out how to determine the URL of the CRM installation. I'm authoring this in a test environment and definitely don't want to have to change things when I move to production. I'm sure I could use a config file, but seems like the plug-in should be able to figure this out at runtime. Anyone have any ideas how to access the URL of the crm service from within a plug-in? Any other ideas? Thanks!

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  • XML file as model for django project

    - by Ankur Chauhan
    Hi, I have a XML file that is managed by other programs, I am writing a web service such that users are able to query this file. In essence i am using a xml based database instead of using sql as the model database in Django. how do i do this? all the tutorials that i find use a sql database in the backend. is there a way to use the xml file as a database.

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  • Data Modeling of Entity with Attributes

    - by StackOverflowNewbie
    I'm storing some very basic information "data sources" coming into my application. These data sources can be in the form of a document (e.g. PDF, etc.), audio (e.g. MP3, etc.) or video (e.g. AVI, etc.). Say, for example, I am only interested in the filename of the data source. Thus, I have the following table: DataSource Id (PK) Filename For each data source, I also need to store some of its attributes. Example for a PDF would be "numbe of pages." Example for audio would be "bit rate." Example for video would be "duration." Each DataSource will have different requirements for the attributes that need to be stored. So, I have modeled "data source attribute" this way: DataSourceAttribute Id (PK) DataSourceId (FK) Name Value Thus, I would have records like these: DataSource->Id = 1 DataSource->Filename = 'mydoc.pdf' DataSource->Id = 2 DataSource->Filename = 'mysong.mp3' DataSource->Id = 3 DataSource->Filename = 'myvideo.avi' DataSourceAttribute->Id = 1 DataSourceAttribute->DataSourceId = 1 DataSourceAttribute->Name = 'TotalPages' DataSourceAttribute->Value = '10' DataSourceAttribute->Id = 2 DataSourceAttribute->DataSourceId = 2 DataSourceAttribute->Name = 'BitRate' DataSourceAttribute->Value '16' DataSourceAttribute->Id = 3 DataSourceAttribute->DataSourceId = 3 DataSourceAttribute->Name = 'Duration' DataSourceAttribute->Value = '1:32' My problem is that this doesn't seem to scale. For example, say I need to query for all the PDF documents along with thier total number of pages: Filename, TotalPages 'mydoc.pdf', '10' 'myotherdoc.pdf', '23' ... The JOINs needed to produce the above result is just too costly. How should I address this problem?

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