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• Initialize virtual attributes

  - by Horace Loeb

  I have an IncomingEmail model with an attachments virtual attribute: class IncomingEmail < ActiveRecord::Base attr_accessor :attachments end I want the attachments virtual attribute to be initialized to [] rather than nil so that I can do: >> i = IncomingEmail.new => #<IncomingEmail id: nil,...) >> i.attachments << "whatever" Without first setting i.attachments to [] (put another way, I want this virtual attribute to default to an empty array rather than nil)

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• What arguments to use to explain why SQL Server is far better then a flat file

  - by jamone

  The higher ups in my company were told by good friends that flat files are the way to go, and we should switch from SQL Server to them for everything we do. We have over 300 servers and hundreds of different databases. From just the few I'm involved with we have 10 billion records in quite a few of them with upwards of 100k new records a day and who knows how many updates... Me and a couple others need to come up with a response saying why we shouldn't do this. Most of our stuff is ASP.NET with some legacy ASP. We thought that making a simple console app that tests/times the same interactions between a flat file (stored on the network) and SQL over the network doing large inserts, searches, updates etc along with things like network disconnects randomly. This would show them how bad flat files can be especially when you are dealing with millions of records. What things should I use in my response? What should I do with my demo code to illustrate this? My sort list so far: Security Concurrent access Performance with large amounts of data Amount of time to do such a massive rewrite/switch Lack of transactions PITA to map relational data to flat files NTFS doesn't support tons of files in a directory well I fear that this will be a great post on the Daily WTF someday if I can't stop it now.

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• Embedding a scripting engine in C++

  - by Jen

  I'm researching how to best extend a C++ application with scripting capability, and I am looking at either Python or JavaScript. User-defined scripts will need the ability to access the application's data model. Have any of you had experiences with embedding these scripting engines? What are some potential pitfalls?

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• MVVM Group Radio Button

  - by LnDCobra

  What is the best way of binding a number of RadioButtons to an enum using MVVM? The only way I can think of is binding each group box's IsChecked to a property, and in the setter of that property assign a value to an enum in the view model. Any help is appreciated.

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• Combobox item style

  - by user373721

  my project is asp.net MVC, using Telerik MVC combobox. I can change the sytle of the first item if I use: var item = combobox.dropDown.$items.first(); item.addClass('test'); Or change all items, using: combobox.dropDown.$items.addClass('test'); But I need to change just specific items (based on a model), I tried: combobox.dropDown.$items[1].addClass('test'); I get this error: Object doesn't support property or method 'addClass'

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• Python modify an xml file

  - by michele

  I have this xml model. link text So I have to add some node (see the text commented) to this file. How I can do it? I have writed this partial code but it doesn't work: xmldoc=minidom.parse(directory) child = xmldoc.createElement("map") for node in xmldoc.getElementsByTagName("Environment"): node.appendChild(child) Thanks in advance.

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• how to specify a BIGINT in a ruby scaffold?

  - by webdestroya

  I am trying to create a model in ruby that uses a BIGINT datatype (as opposed to the INT done by :integer). I have search all over Google, but all I seem to find is "run an SQL statement to alter the table to a BIGINT" - This seems a bit hack-ish to me, so I wanted to know if there was a way to specify a bigint in the ruby system like :big_int or something Any ideas?

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• django: Changing auto_id of ModelForm based form class

  - by Meilo

  Every time I create an instance of the TestForm specified below, I have to overwrite the standard id format with auto_id=True. How can this be done once only in the form class instead? Any hints are very welcome. views.py from django.forms import ModelForm from models import Test class TestForm(ModelForm): class Meta: model = Test def test(request): form = TestForm(auto_id=True)

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• Mapping enum types with Hibernate Annotations

  - by Thiago

  Hi there, I have an enum type on my Java model which I'd like to map to a table on the database. I'm working with Hibernate Annotations and I don't know how to do that. Since the answers I search were rather old, I wonder which way is the best? Thanks in advance

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• Sparse (Pseudo) Infinite Grid Data Structure for Web Game

  - by Ming

  I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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• Is it possible ot mix named pipe with select in perl

  - by Haiyuan Zhang

  I need to write a daemon that supposed to have one TCP socket and one named pipe. Usually if I need to implement a multi IO server with "pure" sockets, the select based multi-IO model is always the one I will choose. so does anyone of you have ever used named pipe in select or you can just tell me it is impossible. thanks in advance.

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• Is MapReduce one form of Continuation-Passing Style (CPS)?

  - by Jeffrey

  As the title says. I was reading Yet Another Language Geek: Continuation-Passing Style and I was sort of wondering if MapReduce can be categorized as one form of Continuation-Passing Style aka CPS. I am also wondering how can CPS utilise more than one computer to perform complex computation. Maybe CPS makes it easier to work with Actor model.

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• HFT strategy coding on hardware

  - by bsobaid

  Hardware accelaration and embedded programming has mostly been used so far to parse datafeed and/or to route orders to exchange. Have there been attempts to write simpler HFT strategies such as equity market-making in hardware? Have they been successful? Which companies are doing this and what kind of programming model is used?

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• ISBNs are used as primary key, now I want to add non-book things to the DB - should I migrate to EAN

  - by fish2000

  I built an inventory database where ISBN numbers are the primary keys for the items. This worked great for a while as the items were books. Now I want to add non-books. some of the non-books have EANs or ISSNs, some do not. It's in PostgreSQL with django apps for the frontend and JSON api, plus a few supporting python command-line tools for management. the items in question are mostly books and artist prints, some of which are self-published. What is nice about using ISBNs as primary keys is that in on top of relational integrity, you get lots of handy utilities for validating ISBNs, automatically looking up missing or additional information on the book items, etcetera, many of which I've taken advantage. some such tools are off-the-shelf (PyISBN, PyAWS etc) and some are hand-rolled -- I tried to keep all of these parts nice and decoupled, but you know how things can get. I couldn't find anything online about 'private ISBNs' or 'self-assigned ISBNs' but that's the sort of thing I was interested in doing. I doubt that's what I'll settle on, since there is already an apparent run on ISBN numbers. should I retool everything for EAN numbers, or migrate off ISBNs as primary keys in general? if anyone has any experience with working with these systems, I'd love to hear about it, your advice is most welcome.

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• Creating a table with an initial element selected

  - by Tony

  I want to create a table which displays in each row a set of data, in addition to a radio button for possible selection. This can be achieved easily by using a simple table model class which extends the DefaultTableModel and a cell renderer and editor class which implements the TableCellRenderer and TableCellEditor interfaces respectively. What I really couldn't manage to do is to make the table to display initially one of the elements (rows) initially selected. It seems straightforward but it isn't...does anybody have a clue about it?

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• Entity Framework foreign relationship issue

  - by Doug Hope

  I've had an entity framework model working for some time. Yesterday, it suddenly started complaining about a foreign key relationship issue during an insert. I've checked the fields and can do a manual insert using the exact field values. But the EF continues to complain. Any ideas what could have happened?

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• Best editor for CodeIgniter?

  - by Rismo

  I'm learning CodeIgniter and I come from Microsoft Visual Studio so I'm used to the auto complete feature. I've been using notepad++ so far but I wonder if anyone knows an editor that works better with CodeIgniter. I would love to see features like: Right-click - Add new model Right-click - Add new view Autocomplete with CodeIgniter helpers and libraries

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• Finding entries belonging to current month (or other months)

  - by dchua

  I have a model (Expense) that contains fields like 'cost'. I'd like to iterate through all my expenses to find the sum of the cost for all entries belonging to a particular month. Is there a way to do it in rails directly? Expense.find(:all, :conditions = .....)

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• Linq to SQL code generator features

  - by Anders Abel

  I'm very fond of Linq to SQL and the programming model it encourages. I think that in many cases when you are in control of both the database schema and the code it is not worth the effort to have different relational and object models for the data. Working with Linq to SQL makes it simple to have type safe data access from .NET, using the partial extension methods to implement business rules. Unfortunately I do not like the dbml designer due to the lack of a schema refresh function. So far I have used SqlMetal, but that lacks the customization options of the dbml designer. Because of that I've started working on a tool which regenerates the whole code file like SqlMetal, but has the ability to do the customizations that are available in the dbml designer (and maybe more in the future). The customizations will be described in an xml file which only contains those parts that shouldn't have default values. This should keep the xml file size down as well as the maintenance burden of it. To help me focus on the right features, I would like to know: What would be your favourite feature in a linq to sql code generator?

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• EF exception: Could not find file CodeGenerationSchema.xsd

  - by DK

  I'm using Entity Framework for a new project (VS 2008, .net 3.5 sp1) and "reasonably happy" with it, especially compared to dataset-based solutions. One of recurring annoyances is "Could not find file CodeGenerationSchema.xsd" exception during application startup. Exception seems to re-appear rather frequently after changes to the model. Googling gives temporary and strange workarounds for this error: Delete .suo file, or Set Options Debugging General Enable Just My Code = On May be someone have more permanent, straightforward fix or can explain the reason of this issue.

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• MongoDB ruby dates

  - by MB

  I have a collection with an index on :created_at (which in this particular case should be a date) From rails what is the proper way to save an entry and then retrieve it by the date? I'm trying something like: Model: field :created_at, :type = Time script: Col.create(:created_at = Time.parse(another_model.created_at).to_s and Col.find(:all, :conditions = { :created_at = Time.parse(same thing) }) and it's not returning anything

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• Html.DropDownList - Disabled/Readonly

  - by ETFairfax

  Hi, What option do I need to set to make a drop down box readonly when using MVCs Html.DropDownList? I've tried things like.... Html.DropDownList("Types", Model.Types, new { _Enabled = "false" }) ...and many different things along this line; alas no joy! I thought this would be an easy.....and it probably is!!!!! Thanks, ETFairfax.

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• need help ,hp class and xml save load edit example.p

  - by jef

  http://www.sendspace.com/file/2zlfgn I have the php files i been trying to get them to save to xml. I have tried $product1=array(); $product1['id'] = new product( "19990","modrl","maf","purpose","war"); only the ID writes to xml. since model,maf etc are sub-elements is there a different way to create the objectarray?

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• How to write a spinlock without using CAS

  - by Martin

  Following on from a discussion which got going in the comments of this question. How would one go about writing a Spinlock without CAS operations? As the other question states: The memory ordering model is such that writes will be atomic (if two concurrent threads write a memory location at the same time, the result will be one or the other). The platform will not support atomic compare-and-set operations.

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• In-app subscription apps

  - by Ron Srebro

  Does anyone know of an app that implemented an in-app subscription? I thought about how the subscription model can be implemented and always ends up with more problems to every possible solution I can think of, so I'm wondering if anyone knows of an app that actually does that. Thanks

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