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• How would you create a notification system like on SO or Facebook in RoR?

  - by Justin Meltzer

  I'm thinking that notifications would be it's own resource and have a has_many, through relationship with the user model with a join table representing the associations. A user having many notifications is obvious, and then a notification would have many users because there would be a number of standardized notifications (a commenting notification, a following notification etc.) that would be associated with many users. Beyond this setup, I'm unsure how to trigger the creation of notifications based on certain events in your application. I'm also a little unsure of how I'd need to set up routing - would it be it's own separate resource or nested in the user resource? I'd find it very helpful if someone could expand on this. Lastly, ajax polling would likely improve such a feature. There's probably some things I'm missing, so please fill this out so that it is a good general resource.

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• 'Recursive' LINQ calls

  - by Sir Psycho

  Hi, I'm trying to build an XML tree of some data with a parent child relationship, but in the same table. The two fields of importance are CompetitionID ParentCompetitionID Some data might be CompetitionID=1, ParentCompetitionID=null CompetitionID=2, ParentCompetitionID=1 CompetitionID=3, ParentCompetitionID=1 The broken query I have simply displays results in a flat format. Seeing that I'm working with XML, some sort of recursive functionality is required. I can do this using recursion, but would like to see the linq version. Any help appreciated. var results = from c1 in comps select new { c.CompetitionID, SubComps= from sc in comps.Where (c2 => c2.CompetitionID == c1.CompetitionID) select sc };

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• Accessing individual HABTM records in a form

  - by Pichan

  I'm building a form in my CakePHP project that lets you edit a company's information. Among all other things, every company has at least one geographical area in which the company operates, but it may have more. The areas are selected individually using select dropdowns. The relationship between companies and areas is HABTM, because I need to be able to change the amount of associated areas without modifying the database. Currently the associations and corresponding data are handled separately, which isn't really a problem but I was wondering how it could be done using as much Cake's own 'automagic' functionality as possible?

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• AutoMapper: How to transform object graph to into?

  - by epitka

  If I have a one-to-many relationship and I want to transorm this into a list of flat Dto-s where some attributes of parent and some of child appear in a dto, is this something that is supported out-of-box with AutoMapper? For example if I have something like this Parent 1. ParentId 2. ParentAttr1 3. List<Child> Child 1. ChildId 2. ChildAttr1 2. ChildAttr2 Dto 1. ParentId 2. ChildId 2. ChildAttr1 3. ChildAttr2 How do I project Parent into a Dto where for each child in parent I will get an instace of Dto? I've setup two maps Parent-Dto and Child-Dto but just doing _mapper.Map(parentInstance) only projects parents attributes. Does this have to be done in two steps, where I would iterate children myself?

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• Grails - Need to restrict fetched rows based on condition on join table

  - by sector7

  Hi guys, I have these two domains Car and Driver which have many-to-many relationship. This association is defined in table tblCarsDrivers which has, not surprisingly, primary keys of both the tables BUT additionally also has a new boolean field deleted. Herein lies the problem. When I find/get query on domain Car, I am fetched all related drivers irrespective of their deleted status in tblCarsDrivers, which is expected. I need to put a clause/constraint to exclude the deleted drivers from the list of fetched records. PS: I tried using an association domain CarDriver in joinTable name but that seems not to work. Apparently it expects only table names, not maps. PPS: I know its unnatural to have any other fields besides the mapping keys in mapping table but this is how I got it and it cant be changed. Car domain is defined as such - class Car { Integer id String name static hasMany = [drivers:Driver] static mapping = { table 'tblCars' version false drivers joinTable:[name: 'tblCarsDrivers',column:'driverid',key:'carid'] } } Thanks!

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• What is your approach to draw a representation of your network ?

  - by Kartoch

  Hello, I'm looking to the community to see how people are drawing their networks, i.e. using symbols to represent complex topology. You can have hardware approach, where every hardware unit are represented. You can also have "entity" approach, where each "service" is shown. Both are interesting but it is difficult to have both on the same schema (but this is needed, especially using virtualization environment). Furthermore, it is difficult to have complex informations on such representation. For instance security parameters (encrypted link, need for authentication) or specific details (protocol type, ports, encapsulation). So my question is: where your are drawing a representation of your network, what is your approach ? Are you using methodology and/or specific softwares ? What is your recommendations for information to put (or not) ? How to deal with the complexity when the network becomes large and/or you want to put a lot of information on it ? Examples and links to good references will be appreciated.

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• Hibernate one-to-one: getId() without fetching entire object

  - by Rob

  I want to fetch the id of a one-to-one relationship without loading the entire object. I thought I could do this using lazy loading as follows: class Foo { @OneToOne(fetch = FetchType.LAZY, optional = false) private Bar bar; } Foo f = session.get(Foo.class, fooId); // Hibernate fetches Foo f.getBar(); // Hibernate fetches full Bar object f.getBar().getId(); // No further fetch, returns id I want f.getBar() to not trigger another fetch. I want hibernate to give me a proxy object that allows me to call .getId() without actually fetching the Bar object. What am I doing wrong?

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• Rails - Why is my custom validation being triggered for only a build command.

  - by adam

  I have a sentence and correction model with a has_one and belongs_to relationship respectively. For some reason when I do def create @sentence = Sentence.find(params[:sentence_id]) @correction = @sentence.build_correction(params[:correction]) a custom validation I wrote for Correction is being called at the build_correction point. the validation is below class Correction < ActiveRecord::Base attr_accessible :text, :sentence_id, :user_id belongs_to :sentence belongs_to :user validate :correction_is_different_than_sentence def correction_is_different_than_sentence errors.add(:text, "can't be the same as the original sentence.") if (text == self.sentence.text) end the problem is for some reason on validation the correction object doesn't have the sentence id set (despite I used the build_correction method) and so it complains "you have nil object .... while executing nil.text" in the if clause in the validation above. So my question is why is the validation occuring for a build command, i thought it only triggers on a create or update. And why isnt the sentence_id getting set?

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• Best practice in Rails when editing scaffold made pages

  - by abegbg

  I have a best practice question. I have two classes, company and category. They have a many-to-many relationship. When clicking a category I shall go to a page showing all companies with the chosen category. Pretty straight forward. My question is: Should I list all the companies on the companies/index.html.erb after filtering the companies in the controller? or Should I list all the companies on the categories/show.html.erb page? or Should I do a completely new page, since it doesn't really fit into any of the two above? Do you generally make a new page when your goal doesn't fit the scaffold made pages or do you use them quite freely? I am working/learning alone with rails, so there are a lot of best practice questions popping up all the time. Cheers Carl

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• Rails object inheritence with belongs_to

  - by Rabbott

  I have a simple has_many/belongs_to relationship between Report and Chart. The issue I'm having is that my Chart model is a parent that has children. So in my Report model I have class Report < ActiveRecord::Base has_many :charts end And my Chart model is a parent, where Pie, Line, Bar all inherit from Chart. I'm not sure where the belongs_to :report belongs within the chart model, or children of chart model. I get errors when I attempt to access chart.report because the object is of type "Class" undefined local variable or method `report' for #< Class:0x104974b90 The Chart model uses STI so its pulling say.. 'Pie' from the chart_type column in the charts table.. what am I missing?

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• Cakephp, Retreive Data for HABTM Models using conditional find

  - by ion

  There are 2 Models: Project & Category that are bind with HABTM relationship. I would like to perform a search from projects controller that can do the following: FIND all DISTINCT Project.scedule WHERE Category.slug != 'uncategorised' Apologies for the syntax, I'm no sequel expert. What I have managed to do is to retrieve all projects that do not belong to Category uncategorised into an array however I'm not sure as to how to search again the array result for DISTINCT Project.schedule values (needed to fill out a form drop down) I hope I made myself clear.

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• How Do I Update a Table From Another Table Only If the Result Count is 1?

  - by Russ Bradberry

  I have a table of 2 tables in a one to many relationship. I want to run an update script that will update the table with the FK of the related table only if there is one result (because if there is multiple then we need to decide which one to use, in another method) Here is what I have so far: UPDATE import_hourly_event_reports i SET i.banner_id = b.banner_id FROM banner b JOIN plan p ON b.plan_id = p.id WHERE b.campain_id = i.campaign_id AND b.size_id = i.size_id AND p.site_id = i.site_id HAVING COUNT(b.banner_id) = 1 As you can see, the HAVING clause doesn't quite work as I'd expect it. I only want to update the row in the import table with the id of the banner from the banner table if the count is equal to 1.

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• Circular Reference for Parent Link on Work Item cannot be resolved by Retry

  - by Atters

  I receive the following error; OH-TFS-Connector-0051: Operation failed getCollectionMetaData. Server Error : TF201063: Adding a Parent link to work item 1737 would result in a circular relationship. To create this link, evaluate the existing links, and remove one of the other links in the cycle. I have completely flattened out the Work Items in the source project. When retrying the migration the timestamp is modified on the pending errors however the issues are not resolved. These Work Items now have no parents or children in the source project. So I'm wondering if the retry list is no longer valid but there doesn't appear to be a away to have it update? I can run the whole migration again, however it takes 5-7 hours to just do the work items so it would be great if there is a quick fix.

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• After C++ - Python or Java?

  - by carleeto

  I'm fast approaching the point in my coding where I would like to quickly write object oriented code in languages other than C++ for a variety of reasons. After a lot of research, my choices have pretty much narrowed down to Python and Java. I'm leaning towards Python because of its relationship to C, but with Java, from what I can see, I get a good introduction to using and creating test suites with Eclipse - there is also Processing which is pulling me towards Java. I'm not the kind of guy to tackle two languages at once, so which one would you recommend and why? What I want at the end is to have an additional language I can use for rapid development. Ease of learning isn't important to me as I'm willing to put in the time regardless. Ability to use the new language widely is.

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• how do I integrate the aspnet_users table that comes with asp.net membership into my existing databa

  - by ooo

  i have a database that already has a users table COLUMNS: userID - int loginName - string First - string Last - string i just installed the asp.net membership table. Right now all of my tables are joined into my users table foreign keyed into the "userId" field How do i integrate asp.net_users table into my schema? here are the ideas i thought of: Add a membership_id field to my users table and on new inserts, include that new field in my users table. This seems like the cleanest way as i dont need to break any existing relationships. break all existing relationship and move all of the fields in my user table into the asp.net_users table. This seems like a pain but ultimately will lead to the most simple, normalized solution any thoughts?

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• Want to save data field from form into two columns of two models.

  - by vette982

  I have a Profile model with a hasOne relationship to a Detail model. I have a registration form that saves data into both model's tables, but I want the username field from the profile model to be copied over to the usernamefield in the details model so that each has the same username. function new_account() { if(!empty($this->data)) { $this->Profile->modified = date("Y-m-d H:i:s"); if($this->Profile->save($this->data)) { $this->data['Detail']['profile_id'] = $this->Profile->id; $this->data['Detail']['username'] = $this->Profile->username; $this->Profile->Detail->save($this->data); $this->Session->setFlash('Your registration was successful.'); $this->redirect(array('action'=>'index')); } } } This code in my Profile controller gives me the error: Undefined property: Profile::$username Any ideas?

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• UML binary association aggregatee has access to aggregator

  - by user314172

  Firstly, I'd like to thank those who answered my previous question ages ago. Currently I'm engaging more in the design phase UMLs, as this is my first medium scale deployment I'm entrusted with. This is extremely simple, but it bugs me so. If (Component) owns (Manager of Component), and (Manager of Component) has a reference to (Component) through which it manages it; how do you fully describe the relationship? I know it is aggregative, but how do you describe (Manager of Component) possessing a reference/pointer to the (Component) that physically owns the (Manager of Component) ? Example: Lidar owns a LidarManager

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• Rails: Best practice to store user settings?

  - by ole_berlin

  Hi, I'm wondering what the best way is to store user settings? For a web 2.0 app I want users to be able to select certain settings. At the moment is it only when to receive email notifications. The easiest way would be to just create a Model "Settings" and have a column for every setting and then have a 1-1 relationship with users. But is there a pattern to solve this better? Is it maybe better to store the info in the user table itself? Or should I use a table with "settings_name" and "settings_value" to be completely open about the type of settings stored there (without having to run any migrations when adding options)? What is your opinion? Thanks

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• Manually Building a Tree in CakePHP

  - by mabwi

  I'm currently working on building an application in CakePHP. There's a quite extensive existing data set that's conceptually a tree, but wasn't previously stored as one. What I mean by that, is there's no real relationship defined in the data. The problem I'm having is getting it to work correctly with the CakePHP tree behaviour. Because I have to set all the values on existing data - as opposed to Cake setting up the structure as elements are inserted - I need to understand how the lft/rght values work. So, I guess the question is: How does the structure data work, specifically the lft/rght values? How do I set it up so that the data comes out rationally, without inserting them one at a time? It's a 2 level tree, with Sections and sub-sections. Thanks for the help

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• has_many conditions

  - by user305270

  c = "(f.profile_id = #{self.id} OR f.friend_id = #{self.id})" c += AND + "(CASE WHEN f.profile_id=#{self.id} THEN f.friend_id ELSE f.profile_id END = p.id)" c += AND + "(CASE WHEN f.profile_id=#{self.id} THEN f.profile_rejected ELSE f.friend_rejected END = 1)" c += AND + "(p.banned = 0)" I need this to be used in a has_many relationship like this: has_many :removed_friends, :conditions => ??? how do i set there the self.id?, or how do i pass there the id? Then i want to use the will_paginate plugin: @profile.removed_friends.paginate(:page => 1, :per_page => 20) Thanks for your help

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• nsfetchedresultscontroller with empty sections

  - by WearyMonkey

  I have a database of People and pets, with a one to many relationship Person Pet Name Name Pet <----- Owner I am using a UITableView backed by Core data and a nsfetchedresultscontroller to display the list of pets, grouped into sections by the owner. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; fetchRequest.entity = [NSEntityDescription entityFromName:@"Pet" inManagedObjectContext:context] NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Owner.name" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSFetchedResultsController *controller = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:@"Owner.name" cacheName:@"Root"]; This works to display all pets under their owners section, however I also want to display the empty sections of People who do not have any pets? Is this possible? Thanks for any help.

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• save object associate to another object automatically

  - by Luca Romagnoli

  Hi i have these classes: class Core < ActiveRecord::Base belongs_to :resource, :polymorphic => true belongs_to :image, :class_name => 'Multimedia', :foreign_key => 'image_id' end class Place < ActiveRecord::Base has_one :core, :as => :resource end If i try do launch this: a = Place.find(5) a.name ="a" a.core.image_id = 24 a.save name is saved. image_id no i want save automatically all changes in records in relationship with place class at a.save command. is possible? thanks

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• FileInputStream and FileOutputStream to the same file: Is a read() guaranteed to see all write()s that "happened before"?

  - by user946850

  I am using a file as a cache for big data. One thread writes to it sequentially, another thread reads it sequentially. Can I be sure that all data that has been written (by write()) in one thread can be read() from another thread, assuming a proper "happens-before" relationship in terms of the Java memory model? Is this behavior documented? EDIT: In my JDK, FileOutputSream does not override flush(), and OutputStream.flush() is empty. That's why I'm wondering... EDIT^2: The streams in question are owned exclusively by a class that I have full control of. Each stream is guaranteed to be accesses by one thread only. My tests show that it works as expected, but I'm still wondering if this is guaranteed and documented. See also this related discussion: http://chat.stackoverflow.com/rooms/17598/discussion-between-hussain-al-mutawa-and-user946850

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• Rails 2.3.5: How does one add an error when it doesn't make sense to put it in a validation?

  - by randombits

  I recently was trying to add errors.add_to_base code in the middle of some model logic and was wondering why it wasn't showing up in my view that was iterating over all errors. I then ran across this e-mail which explains why: http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/e045ec1dead1ff06?pli=1 The question is then, how does one add errors with add_to_base if it doesn't make sense to put them into a validate method? I have some complex logic. The model needs to talk to a has_many relationship which has its own relationships that go through a myriad of conditionals to figure out if a request makes sense. It's nothing that can be tied to a validate method easily. How does one add errors then accordingly?

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• SQL SELECT using in() but excluding others.

  - by Pickledegg

  I have a table called 'countries' linked to another table 'networks' with a many to many relationship: countries countries_networks networks +-------------+----------+ +-------------+----------+ +-------------+---------------+ | Field | Type | | Field | Type | | Field | Type | +-------------+----------+ +-------------+----------+ +-------------+---------------+ | id | int(11) | | id | int(11) | | id | int(11) | | countryName | char(35) | | country_id | int(11) | | name | varchar(100) | +-------------+----------+ | network_id | int(11) | | description | varchar(255) | To retrieve all countries that have a network_id of 6 & 7, I just do the following: ( I could go further to use the networks.name but I know the countries_networks.network_id so i just use those to reduce SQL.) SELECT DISTINCT countryName FROM countries AS Country INNER JOIN countries_networks AS n ON Country.id = n.country_id WHERE n.network_id IN (6,7) This is fine, but I then want to retrieve the countries with a network_id of JUST 8, and no others. I'ver tried the following but its still returning networks with 6 & 7 in. Is it something to do with my JOIN? SELECT DISTINCT countryName FROM countries AS Country INNER JOIN countries_networks AS n ON Country.id = n.country_id WHERE n.network_id IN (8) AND n.network_id not IN(6,7) Thanks.

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