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  • Should this even be a has_many :through association?

    - by GoodGets
    A Post belongs_to a User, and a User has_many Posts. A Post also belongs_to a Topic, and a Topic has_many Posts. class User < ActiveRecord::Base has_many :posts end class Topic < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base belongs_to :user belongs_to :topic end Well, that's pretty simple and very easy to set up, but when I display a Topic, I not only want all of the Posts for that Topic, but also the user_name and the user_photo of the User that made that Post. However, those attributes are stored in the User model and not tied to the Topic. So how would I go about setting that up? Maybe it can already be called since the Post model has two foreign keys, one for the User and one for the Topic? Or, maybe this is some sort of "one-way" has_many through assiociation. Like the Post would be the join model, and a Topic would has_many :users, :through = :posts. But the reverse of this is not true. Like a User does NOT has_many :topics. So would this even need to be has_many :though association? I guess I'm just a little confused on what the controller would look like to call both the Post and the User of that Post for a give Topic. Edit: Seriously, thank you to all that weighed in. I chose tal's answer because I used his code for my controller; however, I could have just as easily chosen either j.'s or tim's instead. Thank you both as well. This was so damn simple to implement, and I think today marks the day that I'm beginning to fall in love with rails.

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  • Why is it bad to use boolean flags in databases? And what should be used instead?

    - by David Chanin
    I've been reading through some of guides on database optimization and best practices and a lot of them suggest not using boolean flags at all in the DB schema (ex http://forge.mysql.com/wiki/Top10SQLPerformanceTips). However, they never provide any reason as to why this is bad. Is it a peformance issue? is it hard to index or query properly? Furthermore, if boolean flags are bad, what should you use to store boolean values in a database? Is it better to store boolean flags as an integer and use a bitmask? This seems like it would be less readable.

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  • The finest way to store the HardCore Data i android

    - by david
    Hi All! I am working on an application where I have a long listing of different states approximately 20 states and each state consisting of several zones in addition to the weather forcast of each zone eventually. Now the thing is that I have already created the Listing of hardcore data in a list view of all the states. Again I need to add the hardcore data of several zones for each state(min 4 to 5 zones/ state). So , now I am wondering that whether I have to create the separate classes with hardcore names of all the zones in each state or is there any easy way out for doing the same. It would be great if anyone having the idea can tell me. Thanks, david

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  • Testing system where App-level and Request-level IoC containers exist

    - by Bobby
    My team is in the process of developing a system where we're using Unity as our IoC container; and to provide NHibernate ISessions (Units of work) over each HTTP Request, we're using Unity's ChildContainer feature to create a child container for each request, and sticking the ISession in there. We arrived at this approach after trying others (including defining per-request lifetimes in the container, but there are issues there) and are now trying to decide on a unit testing strategy. Right now, the application-level container itself is living in the HttpApplication, and the Request container lives in the HttpContext.Current. Obviously, neither exist during testing. The pain increases when we decided to use Service Location from our Domain layer, to "lazily" resolve dependencies from the container. So now we have more components wanting to talk to the container. We are also using MSTest, which presents some concurrency dilemmas during testing as well. So we're wondering, what do the bright folks out there in the SO community do to tackle this predicament? How does one setup an application that, during "real" runtime, relies on HTTP objects to hold the containers, but during test has the flexibility to build-up and tear-down the containers consistently, and have the ServiceLocation bits get to those precise containers. I hope the question is clear, thanks!

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  • Reasons to start a new project in COBOL

    - by luvieere
    Are there any feasible reasons to start a new project in COBOL? What benefits of this language one would find convincing enough to start a new project in it? I'm thinking more about viewing the language in terms of Behavior Driven Development, something related to the steps involved in using a framework such as Cucumber, only that behavior description and step definition would be integrated into one unit by using tha language's features.

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  • Best solution for a comment table for multiple content types

    - by KRTac
    I'm currently designing a comments table for a site I'm building. Users will be able to upload images, link videos and add audio files to the profile. Each of these types of content must be commentable. Now I'm wondering what's the best approach to this. My current options are: 1. to have one big comments table and a link tables for every content type (comments_videos, ...) with comment_id and _id. 2. to have comments separated by the type of content their for. So each type of content would have his own comments table with the comments for that type.

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  • Options for keeping models and the UI in sync (in a desktop application context)

    - by Benju
    In my experience I have only had 2 patterns work for large-scale desktop application development when trying to keep the model and UI in sync. 1-An eventbus approach via a shared eventbus command objects are fired (ie:UserDemographicsUpdatedEvent) and have various parts of the UI update if they are bound to the same user object updated in this event. 2-Attempt to bind the UI directly to the model adding listeners to the model itself as needed. I find this approach rather clunky as it pollutes the domain model. Does anybody have other suggestions? In a web application with something like JSP binding to the model is easy as you ussually only care about the state of the model at the time your request comes in, not so in a desktop type application. Any ideas?

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  • Collaborative Filtering Program: What to do for a Pearson Score When There Isn't Enough Data

    - by Mike
    I'm building a recommendation engine using collaborative filtering. For similarity scores, I use a Pearson correlation. This is great most of the time, but sometimes I have users that only share a 1 or 2 fields. For example: User 1{ a: 4 b: 2 } User 2{ a: 4 b: 3 } Since this is only 2 data points, a Pearson correlation would always be 1 (a straight line or perfect correlation). This obviously isn't what I want, so what value should I use instead? I could just throw away all instances like this (give a correlation of 0), but my data is really sparse right now and I don't want to lose anything. Is there any similarity score I could use that would fit in with the rest of my similarity scores (all Pearson)?

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  • Bejeweled Blitz - How does it assert there is always a move?

    - by EvilTeach
    I have been playing Bejeweled Blitz for a while now. Yes, it is an addiction. In thinking about the game, I have observed that on some boards, the bottom runs dry (no moves) leaving only the top part of the board playable. Frequently that part of the board drys up, and one is left with moves in area cleared by the last move. The board never runs completely dry, so clearly the program is doing some sorts of calculation that allows it to choose what to drop to prevent it from running dry. I have noticed in this 'mode' that it is very common for the algorithm to drop jewels which causes more non-dry area to appear in the horizontal area. Perhaps less frequent is a drop which seems designed to open up the bottom part of the board again. So my question is "How would one go about designing an algorithm guarantee that there is always a move available.?"

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  • How to properly name record creation(insertion) datetime field ?

    - by alpav
    If I create a table with datetime default getdate() field that is intended to keep date&time of record insertion, which name is better to use for that field ? I like to use Created and I've seen people use DateCreated or CreateDate. Other possible candidates that I can think of are: CreatedDate, CreateTime, TimeCreated, CreateDateTime, DateTimeCreated, RecordCreated, Inserted, InsertedDate, ... From my point of view anything with Date inside name looks bad because it can be confused with date part in case if I have 2 fields: CreateDate,CreateTime, so I wonder if there are any specific recommendations/standards in that area based on real reasons, not just style, mood or consistency. Of course, if there are 100 existing tables and this is table 101 then I would use same naming convention as used in those 100 tables for the sake of consistency, but this question is about first table in first database in first server in first application.

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  • Is Multiple Iterators is possible in php?

    - by artvolk
    Good day! I know that C# allows multiple iterators using yield, like described here: http://stackoverflow.com/questions/1754041/is-multiple-iterators-is-possible-in-c In PHP there is and Iterator interface. Is it possible to implement more than one iteration scenario for a class?

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  • Producer/consumer in Grails?

    - by Mulone
    Hi all, I'm trying to implement a Consumer/Producer app in Grails, after several unsuccessful attempts at implementing concurrent threads. Basically I want to store all the events coming from a clients (through separate AJAX calls) in a single queue and then process such a queue in a linear way as soon as new events are added. This looks like a Producer/Consumer problem: http://en.wikipedia.org/wiki/Producer-consumer_problem How can I implement this in Grails (maybe with a timer or even better by generating an event 'process queue')? Basically I'd like to a have a singleton service waiting for new events in the queue and processing them linearly (even if the queue is loaded by several concurrent processes). Any hints? Cheers!

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  • Storing old previous year data in Rails?

    - by Millisami
    Hi, I'm developing an app which has massive data entries. Its like Campaign which has attrs like rate_per_sq_feet, start_date, end_date. i.e it will have max date of around 30 days. Once the campaign is finished, its done and another starts. Now I'm confused that how to store those campaigns as reports so that its not accessed regurlarly. What I mean is to store in such a way that it will act like report on later years to come? Its something like fiscal year on accounts where the previous year reports are stored with all the calculations done so that when retrieved later, all the algorithms and calculations shouldn't be performed. Something like frozen data??

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  • GORM ID generation and belongsTo association ?

    - by fabien-barbier
    I have two domains : class CodeSetDetail { String id String codeSummaryId static hasMany = [codes:CodeSummary] static constraints = { id(unique:true,blank:false) } static mapping = { version false id column:'code_set_detail_id', generator: 'assigned' } } and : class CodeSummary { String id String codeClass String name String accession static belongsTo = [codeSetDetail:CodeSetDetail] static constraints = { id(unique:true,blank:false) } static mapping = { version false id column:'code_summary_id', generator: 'assigned' } } I get two tables with columns: code_set_detail: code_set_detail_id code_summary_id and code_summary: code_summary_id code_set_detail_id (should not exist) code_class name accession I would like to link code_set_detail table and code_summary table by 'code_summary_id' (and not by 'code_set_detail_id'). Note : 'code_summary_id' is define as column in code_set_detail table, and define as primary key in code_summary table. To sum-up, I would like define 'code_summary_id' as primary key in code_summary table, and map 'code_summary_id' in code_set_detail table. How to define a primary key in a table, and also map this key to another table ?

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  • Reference platform specific System.Data.SQLite

    - by Dmitriy Nagirnyak
    I am using SQLite for the unit testing and might use it as a database for local development/staging. The System.Data.SQLite has basically 2 versions: x86 and x64. Correct one should be used for the specific platform. I have 64 bit Win7, other guys in the team might use 32-bit OSs. The server's platform is not known at this stage. If I use 32-bit version of the assembly on 64-bit platform I get BadImageFormatException: Could not load file or assembly 'System.Data.SQLite'. I believe similar will happen trying to use 64-bit assembly on 32-bit platform. So my question is what is the best way to reference the SQLite assembly so that it does not depend on the platform and people can just use it? It is ok to use 32-bit version of assembly on a 64-bit platform (Maybe there is a switch for that somewhere?).

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  • Getting website data into Adobe InDesign

    - by Magnus Smith
    I'd like our magazine team to be able to download website data in a file that Adobe InDesign can read. They can then import/open the file, make a few tweaks, and cut out a vast deal of repetitive manual labour (they currently use copy&paste for a few hours). After a brief Google I note that v2 of InDesign can import/export XML so perhaps that is my best bet? Are there any alternatives, and can anyone offer any advice on them? I am using a PC, and the magazine team are on Macs; testing will be tiresome I fear. The data we wish to format is fairly simple - a title followed by a short chunk of text (repeated about 50 times, say). I'll ask about importing images later. Thanks for your help. I will return to Google now, but it would be great if anyone can point me in a more specific direction first!

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  • Efficient algorithm for creating an ideal distribution of groups into containers?

    - by Inshim
    I have groups of students that need to be allocated into classrooms of a fixed capacity (say, 100 chairs in each). Each group must only be allocated to a single classroom, even if it is larger than the capacity (ie there can be an overflow, with students standing up) I need an algorithm to make the allocations with minimum overflows and under-capacity classrooms. A naive algorithm to do this allocation is horrendously slow when having ~200 groups, with a distribution of about half of them being under 20% of the classroom size. Any ideas where I can find at least some good starting point for making this algorithm lightning fast? Thanks!

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  • What is your custom exception hierrarchy?

    - by bonefisher
    My question is: how would you create exception hierarchy in your application? Designing the architecture of an application, from my perspective, we could have three types of exceptions: the built-in (e.g.: InvalidOperationException) custom internal system faults (DB transaction failed on commit, DbTransactionFailedException) custom business exceptions (BusinessRuleViolationException) Class hierarchy: Exception MyAppInternalException DbTransactionFailedException MyServerTimeoutException ... MyAppBusinessRuleViolationException UsernameAlreadyExistsException ... where only MyAppInternalException & MyAppBusinessRuleViolationException would be catched.

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  • Data sync solution?

    - by user321088
    For some security issues I'm in an envorinment where third party apps can't access my DB. For this reason I should have some service/tool/script (dunno what yet... i'm open to the best option, still reading to see what I'm gonna do...) which enables me to generate on a regular basis(daily, weekly, monthly) some csv file with all new/modified records for a certain application. I should be able to automate this process and also export at any time a new file. So it should keep track for each application which records he still needs. Each application will need some data in some other format (csv/xls/sql), also some fields will be needed for some application and some aren't... It should be fairly flexible... What is the best option for me? Creating some custom tables for each application? Based on that extracting modified data?

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  • CSS for top right corner of the page

    - by user102533
    How would I have a top right corner div as shown in the image. I want to do something similar though not exactly the same. I think the text is not an image. Also, I have seen some websites that has a page hover effect when a mouse is over the top right section. Any idea how to do that?

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