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  • Explain "Leader/Follower" Pattern

    - by Alex B
    I can't seem to find a good explanation of "Leader/Follower" pattern. All explanations either simply refer to it in the context of some problem, or are completely meaningless. Can anyone explain to the the mechanics of how this pattern works, and why and how it improves performance over more traditional asynchronous IO models? Examples and links to diagrams are appreciated too.

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  • ASP.NET MVC validation in weakly typed views

    - by Eedoh
    Hello. I have a problem validating data on view that is not strongly typed. I'm updating data from 3 different models on that view, and I have validation methods that work on them, but I don't know how to display the validation message. Where should I put validation messages (on strongly typed views I put them in ModelState, I presume that does not make sense in this case), and how should I display them (I doubt that I will be able to use "validationmessagefor", maybe "validationmessage" somehow)?

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  • Trouble using South with Django and Heroku

    - by Dan
    I had an existing Django project that I've just added South to. I ran syncdb locally. I ran manage.py schemamigration app_name locally I ran manage.py migrate app_name --fake locally I commit and pushed to heroku master I ran syncdb on heroku I ran manage.py schemamigration app_name on heroku I ran manage.py migrate app_name on heroku I then receive this: $ heroku run python notecard/manage.py migrate notecards Running python notecard/manage.py migrate notecards attached to terminal... up, run.1 Running migrations for notecards: - Migrating forwards to 0005_initial. > notecards:0003_initial Traceback (most recent call last): File "notecard/manage.py", line 14, in <module> execute_manager(settings) File "/app/lib/python2.7/site-packages/django/core/management/__init__.py", line 438, in execute_manager utility.execute() File "/app/lib/python2.7/site-packages/django/core/management/__init__.py", line 379, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "/app/lib/python2.7/site-packages/django/core/management/base.py", line 191, in run_from_argv self.execute(*args, **options.__dict__) File "/app/lib/python2.7/site-packages/django/core/management/base.py", line 220, in execute output = self.handle(*args, **options) File "/app/lib/python2.7/site-packages/south/management/commands/migrate.py", line 105, in handle ignore_ghosts = ignore_ghosts, File "/app/lib/python2.7/site-packages/south/migration/__init__.py", line 191, in migrate_app success = migrator.migrate_many(target, workplan, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 221, in migrate_many result = migrator.__class__.migrate_many(migrator, target, migrations, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 292, in migrate_many result = self.migrate(migration, database) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 125, in migrate result = self.run(migration) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 99, in run return self.run_migration(migration) File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 81, in run_migration migration_function() File "/app/lib/python2.7/site-packages/south/migration/migrators.py", line 57, in <lambda> return (lambda: direction(orm)) File "/app/notecard/notecards/migrations/0003_initial.py", line 15, in forwards ('user', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['auth.User'])), File "/app/lib/python2.7/site-packages/south/db/generic.py", line 226, in create_table ', '.join([col for col in columns if col]), File "/app/lib/python2.7/site-packages/south/db/generic.py", line 150, in execute cursor.execute(sql, params) File "/app/lib/python2.7/site-packages/django/db/backends/util.py", line 34, in execute return self.cursor.execute(sql, params) File "/app/lib/python2.7/site-packages/django/db/backends/postgresql_psycopg2/base.py", line 44, in execute return self.cursor.execute(query, args) django.db.utils.DatabaseError: relation "notecards_semester" already exists I have 3 models. Section, Semester, and Notecards. I've added one field to the Notecards model and I cannot get it added on Heroku. Thank you.

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  • AMQP subscriber inside Rails app

    - by Fotios
    Is it possible to start an AMQP subscriber with my Rails app? Possibly through an initializer or something. I'd like to have it running at the same time that can also interact with Rails models. Below is a pseudo-code example of what I mean. queue.subscribe do |msg,body| Foo.create(....) end

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  • Jquery AJAX: How to display the Flash error message when validation on the server side fails?

    - by Shripad K
    I am using the Jquery form plugin to submit the form via ajax. I have set up validations on the server side in my models. Now when the validation fails i want to display the same flash[:error] message to the user using ajax. If the validation succeeds I can display the flash[:notice] as it is available after the request is completed. How do i go about displaying flash[:error]?

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  • How do I use a string as a keyword argument?

    - by Issac Kelly
    Specifically, I'm trying to use a string to arbitrairly filter the ORM. I've tried exec and eval solutions, but I'm running into walls. The code below doesn't work, but it's the best way I know how to explain where I'm trying to go from gblocks.models import Image f = 'image__endswith="jpg"' # Would be scripted in another area, but passed as text <user input> d = Image.objects.filter(f) #for the non-django pythonistas: d = Image.objects.filter(image__endswith="jpg") # would be the non-dynamic equivalent.

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  • django admin site - filtering available objects for user

    - by JPG
    I have models that belong to some 'group' (Company class). I want to add users, who will also belong to a one group and should be able to edit/manage/add objects with membership in associated group. something like: class Company() class Something() company = ForeignKey(Company) user Microsoft_admin company = ForeignKey(Company) and this user should only see and edit objects belonging to associated Company in the Admin Interface. How to acomplish that?

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  • Doctrine-CLI database creation issue.

    - by gokujou
    I have Doctrine setup in my Zend Framework application and I built my schema YAML file. But when I tell Doctrine to build the tables it says it does but it doesn't actually make them. It creates the models, and will create the DB but it will not populate the DB with the tables and throws no errors. Does anyone have a guess or know why this is not working? Thank you.

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  • Trouble with ASP.NET MVC auto-scaffolder template

    - by DanM
    I'm trying to write an auto-scaffolder template for Index views. I'd like to be able to pass in a collection of models or view-models (e.g., IQueryable<MyViewModel>) and get back an HTML table that uses the DisplayName attribute for the headings (th elements) and Html.Display(propertyName) for the cells (td elements). Each row should correspond to one item in the collection. Here's what I have so far: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %> <% var items = (IQueryable<TestProj.ViewModels.TestViewModel>)Model; // How do I make this generic? var properties = items.First().GetMetadata().Properties .Where(pm => pm.ShowForDisplay && !ViewData.TemplateInfo.Visited(pm)); %> <table> <tr> <% foreach(var property in properties) { %> <th> <%= property.DisplayName %> </th> <% } %> </tr> <% foreach(var item in items) { HtmlHelper itemHtml = ????; // What should I put in place of "????"? %> <tr> <% foreach(var property in properties) { %> <td> <%= itemHtml.Display(property.DisplayName) %> </td> <% } %> </tr> <% } %> </table> Two problems with this: I'd like it to be generic. So, I'd like to replace var items = (IQueryable<TestProj.ViewModels.TestViewModel>)Model; with var items = (IQueryable<T>)Model; or something to that effect. A property Html is automatically created for me when the view is created, but this HtmlHelper applies to the whole collection. I need to somehow create an itemHtml object that applies just to the current item in the foreach loop. I'm not sure how to do this, however, because the constructors for HtmlHelper don't take a Model object. How do I solve these two problems?

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  • Rails 3 Abstract Class vs Inherited Class

    - by R. Yanchuleff
    In my rails 3 model, I have two classes: Product, Service. I want both to be of type InventoryItem because I have another model called Store and Store has_many :InventoryItems This is what I'm trying to get to, but I'm not sure how to model this in my InventoryItem model and my Product and Service models. Should InventoryItem just be a parent class that Product and Service inherit from, or should InventoryItem be modeled as a class abstract of which Product and Service extend from. Thanks in advance for the advice!

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  • Ado.net entity model problem

    - by ognjenb
    public ActionResult Index() { using (testEntities korisnici = new testEntities()) { my_aspnet_users user = new my_aspnet_users(); user = from i in korisnici.my_aspnet_users select i; return View(user); } } Error: Cannot implicitly convert type 'System.Linq.IQueryable' to 'MyApp.Models.my_aspnet_users'. An explicit conversion exists (are you missing a cast?)

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  • Metaprogramming ActiveRecord Rails

    - by Dimitar Vouldjeff
    Hi, I have the following code in my project`s lib directory module Pasta module ClassMethods def self.has_coordinates self.send :include, InstanceMethods end end module InstanceMethods def coordinates [longitude ||= 43.0, latitude ||= 25.0] end end ActiveRecord::Base.extend ClassMethods end And it should create a class method for ActiveRecord::Base - has_coordinates - which I can "assign" to models... But I receive the error undefined local variable or method 'has_coordinates' Thanks in advance!

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  • Define Rails Model Persistent Attributes in Model File

    - by Kevin Sylvestre
    I recently played with MongoDB in Rails using Mongoid. I like the ability to define attributes for models within the model file (as opposed to in migrations): class Person include Mongoid::Document field :name, :type => String field :birthday, :type => Date end For projects that cannot use a schema-less database, does a similar feature exist? Any gems or plugins that generate schemas from a similar syntax would be greatly appreciated. Thanks.

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  • Which is more flexible in regards to database changes, EF 4 or Linq to SQL

    - by JBeckton
    Reading about both Linq to SQL and Entity Framework I have developed the impression that EF is more suitable for apps that get data from multiple data sources. But as I am reading about MVC2 models I see an example where EF is more loosely coupled with your data model. If I have to add or remove some columns from a table then what is involved in updating my model or DAL with each of these implementations?

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  • How to implement a caching model without violating MVC pattern?

    - by RPM1984
    Hi Guys, I have an ASP.NET MVC 3 (Razor) Web Application, with a particular page which is highly database intensive, and user experience is of the upmost priority. Thus, i am introducing caching on this particular page. I'm trying to figure out a way to implement this caching pattern whilst keeping my controller thin, like it currently is without caching: public PartialViewResult GetLocationStuff(SearchPreferences searchPreferences) { var results = _locationService.FindStuffByCriteria(searchPreferences); return PartialView("SearchResults", results); } As you can see, the controller is very thin, as it should be. It doesn't care about how/where it is getting it's info from - that is the job of the service. A couple of notes on the flow of control: Controllers get DI'ed a particular Service, depending on it's area. In this example, this controller get's a LocationService Services call through to an IQueryable<T> Repository and materialize results into T or ICollection<T>. How i want to implement caching: I can't use Output Caching - for a few reasons. First of all, this action method is invoked from the client-side (jQuery/AJAX), via [HttpPost], which according to HTTP standards should not be cached as a request. Secondly, i don't want to cache purely based on the HTTP request arguments - the cache logic is a lot more complicated than that - there is actually two-level caching going on. As i hint to above, i need to use regular data-caching, e.g Cache["somekey"] = someObj;. I don't want to implement a generic caching mechanism where all calls via the service go through the cache first - i only want caching on this particular action method. First thought's would tell me to create another service (which inherits LocationService), and provide the caching workflow there (check cache first, if not there call db, add to cache, return result). That has two problems: The services are basic Class Libraries - no references to anything extra. I would need to add a reference to System.Web here. I would have to access the HTTP Context outside of the web application, which is considered bad practice, not only for testability, but in general - right? I also thought about using the Models folder in the Web Application (which i currently use only for ViewModels), but having a cache service in a models folder just doesn't sound right. So - any ideas? Is there a MVC-specific thing (like Action Filter's, for example) i can use here? General advice/tips would be greatly appreciated.

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  • Casting objects in C# (ASP.Net MVC)

    - by Mortanis
    I'm coming from a background in ColdFusion, and finally moving onto something modern, so please bear with me. I'm running into a problem casting objects. I have two database tables that I'm using as Models - Residential and Commercial. Both of them share the majority of their fields, though each has a few unique fields. I've created another class as a container that contains the sum of all property fields. Query the Residential and Commercial, stuff it into my container, cunningly called Property. This works fine. However, I'm having problems aliasing the fields from Residential/Commercial onto Property. It's quite easy to create a method for each property: fillPropertyByResidential(Residential source) and fillPropertyByCommercial(Commercial source), and alias the variables. That also works fine, but quite obviously will copy a bunch of code - all those fields that are shared between the two main Models. So, I'd like a generic fillPropertyBySource() that takes the object, and detects if it's Residential or Commercial, fills the particular fields of each respective type, then do all the fields in common. Except, I gather in C# that variables created inside an If are only in the scope of the if, so I'm not sure how to do this. public property fillPropertyBySource(object source) { property prop = new property(); if (source is Residential) { Residential o = (Residential)source; //Fill Residential only fields } else if (source is Commercial) { Commercial o = (Commercial)source; //Fill Commercial only fields } //Fill fields shared by both prop.price = (int)o.price; prop.bathrooms = (float)o.bathrooms; return prop; } "o" being a Commercial or Residential only exists within the scope of the if. How do I detect the original type of the source object and take action? Bear with me - the shift from ColdFusion into a modern language is pretty..... difficult. More so since I'm used to procedural code and MVC is a massive paradigm shift. Edit: I should include the error: The name 'o' does not exist in the current context For the aliases of price and bathrooms in the shared area.

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  • How can I validate two or more fields in combination?

    - by DR
    I'm using JPA 2.0/Hibernate validation to validate my models. I now have a situation where the combination of two fields has to be validated: public class MyModel { public Integer getValue1() { //... } public String getValue2() { //... } } The model is invalid if both getValue1() and getValue2() are null and valid otherwise. How can I perform this kind of validation with JPA 2.0/Hibernate? With a simple @NotNull annotation both getters must be non-null to pass validation.

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  • MVC 4 Tutorial Error

    - by yiati
    I am currently following along with http://www.asp.net/mvc/tutorials/mvc-4/getting-started-with-aspnet-mvc4/accessing-your-model's-data-from-a-controller to get a grasp of MVC 4. I am trying to add the MoviesController, but whenever I do I receive an error that says... "Unable to retrieve metadata for 'MvcMovie.Models.Movie' unrecognized configuration section entityFramework (C:\Users\User\AppData\Local\Temp\tmp4FFB.tmp line 76)" The last thing I did before this was change the Web.config file from the end of the previous page in the tutorial.

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  • Django context processor gets AnonymousUser

    - by myfreeweb
    instead of User. def myview(request): return render_to_response('tmpl.html', {'user': User.objects.get(id=1}) works fine and passes User to template. But def myview(request): return render_to_response('tmpl.html', {}, context_instance=RequestContext(request)) with a context processor def user(request): from django.contrib.auth.models import User return {'user': User.objects.get(id=1)} passes AnonymousUser, so I can't get the variables I need :( What's wrong?

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  • Creating relationship between two model instances

    - by Lowgain
    This is probably pretty simple, but here: Say I've got two models, Thing and Tag class Thing < ActiveRecord::Base has_and_belongs_to_many :tags end class Tag < ActiveRecord::Base has_and_belongs_to_many :things end And I have an instance of each. I want to link them. Can I do something like: @thing = Thing.find(1) @tag = Tag.find(1) @thing.tags.add(@tag) If not, what is the best way to do this? Thanks!

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