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• [Rails3] How to do multiple many to many relationships between the same two tables.

  - by Kurt

  Hi. I have a model of a club where I want to model the two entities Meeting and Member. There are actually two many-to-many relationships between these entities though, as for any meeting a Member can either be a Speaker or a Guest. Now I am an OO thinker, so would normally just create the two classes and each one would just have two arrays of the other inside, but rails is making me think a bit more data centric here, so I realise I need to break these M2M relationships up with join tables Speakers and Guests which I have done, but now I am having trouble describing the relationships in the models. The two join table models both have "belongs_to :meeting" and "belongs_to :member" and I think that should be sufficient. I am not however sure about the Meeting and Member models though. Each one has "has_many :guests" and "has_many: speakers" but I am not sure if I also want to go: has_many :members, :through = :guests has_many :members, :through = :speakers But I suspect that this is like declaring two "members" that will clash. I also thought about: has_many :guests, :through = :guests has_many :speakers, :through = :speakers Does that make sense? How would ActiveRecord know that they are in fact Members? I have found heaps of examples of polymorphic m2m relationships and m2m relationships where 1 table references itself, but no good examples to help me mode this situation where two separate tables have two different m2m relationships. Anyone got any tips?

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• Post MIX10 Decompression

  - by Dave Campbell

  With a big dose of reality, I walked into this place this morning and found out "yeah, I really do write .NET web apps and MS Access for a living" :( ... but it pays the bills and I've gotten *way* used to eating 3 times a day :) MIX10 was great, although the buzz didn't seem as big as MIX09, and I'm not sure why. It also seemed like a different crowd and other folks I talked to agreed with that. Of course now I can outwardly admit that the "Windows Phone 7 Series" is programmed with Silverlight ... how cool is that? I've been biting my tongue about that info for over a month! I cloistered myself in Ballroom A for the week, not counting the Keynotes. That's where the phone sessions were located. I tried to collect the full set, but ended up bailing on the last one because it was ending at the time that MIX10 was ending, and I hadn't spent a whole lot of time in 'The Commons'. I met a bunch of folks I've blogged about, or exchanged email with, and that's always fun. Renewed associations with folks I only see once or twice a year and way too long a list and don't want to mention some and leave off others... I did have an opportunity to meet Charles Petzold... wow that was interesting... I got into Windows development through Charles' Programming Windows 3.1 book 'back in the day' ... couldn't find anyone at Honeywell wanted to join my journey, so it was just me and 'Chuck' :) ... read every word of that book more than once... all marked up, tags sticking out of it. And now he's writing a WP7 book ... gotta get it: Free ebook: Programming Windows Phone 7 Series (DRAFT Preview) I went through my Big List-o-BlogsTM last night and it took over 2 hours because of all the new content since MIX10. I've got 90 posts tagged as of 9PM on 3/21. If everybody stopped right now, it would take me 9 days to push what I have now, so you'll have to be patient! I had another event on Thursday that was *extremely* tiring, so I ended up staying over another night. I drove back into the strip on Friday morning to try to find a non-cheesy souvenir for my wife, and didn't find much. Then I went to Blueberry Hill restaurant for 3 eggs, 3 strips of bacon, and 3 awesome potato pancakes. Check them out if you have time! And then hit the road. In case anyone is wondering, the 2-1/2 hour drive I took across Hoover Dam on Sunday afternoon only took 30 minutes on Friday afternoon... that was a more normal trip! I thoroughly enjoyed the time I spent with everyone. Thanks to John Papa and his crew for the great Insider's party on Monday night... the Blues Brothers were a fun surprise and they did a good job! And the swag was great... thanks to all the contributors for a fun evening at their expense! All I can say is stay tuned, go to live.visitmix.com/videos and watch everything, get the phone tools, start working... everything's different and everything's fun... jump in, it's all Silverlight! Stay in the 'Light! Technorati Tags: Silverlight    Silverlight 4    Windows Phone     MIX10

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• PASS: The Legal Stuff

  - by Bill Graziano

  I wanted to give a little background on the legal status of PASS.  The Professional Association for SQL Server (PASS) is an American corporation chartered in the state of Illinois.  In America a corporation has to be chartered in a particular state.  It has to abide by the laws of that state and potentially pay taxes to that state.  Our bylaws and actions have to comply with Illinois state law and United States law.  We maintain a mailing address in Chicago, Illinois but our headquarters is currently in Vancouver, Canada. We have roughly a dozen people that work in our Vancouver headquarters and 4-5 more that work remotely on various projects.  These aren’t employees of PASS.  They are employed by a management company that we hire to run the day to day operations of the organization.  I’ll have more on this arrangement in a future post. PASS is a non-profit corporation.  The term non-profit and not-for-profit are used interchangeably.  In a for-profit corporation (or LLC) there are owners that are entitled to the profits of a company.  In a non-profit there are no owners.  As a non-profit, all the money earned by the organization must be retained or spent.  There is no money that flows out to shareholders, owners or the board of directors.  Any money not spent in furtherance of our mission is retained as financial reserves. Many non-profits apply for tax exempt status.  Being tax exempt means that an organization doesn’t pay taxes on its profits.  There are a variety of laws governing who can be tax exempt in the United States.  There are many professional associations that are tax exempt however PASS isn’t tax exempt.  Because our mission revolves around the software of a single company we aren’t eligible for tax exempt status. PASS was founded in the late 1990’s by Microsoft and Platinum Technologies.  Platinum was later purchased by Computer Associates. As the founding partners Microsoft and CA each have two seats on the Board of Directors.  The other six directors and three officers are elected as specified in our bylaws. As a non-profit, our bylaws layout our governing practices.  They must conform to Illinois and United States law.  These bylaws specify that PASS is governed by a Board of Directors elected by the membership with two members each from Microsoft and CA.  You can find our bylaws as well as a proposed update to them on the governance page of the PASS web site. The last point that I’d like to make is that PASS is completely self-funded.  All of our $4 million in revenue comes from conference registrations, sponsorships and advertising.  We don’t receive any money from anyone outside those channels.  While we work closely with Microsoft we are independent of them and only derive a very small percentage of our revenue from them.

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• How to Link VS2010 Database Project and LINQ to SQL

  - by Jason

  As I am working with the new database projects in VS2010, and as I am learning LINQ to SQL, I am curious as to the best way to link the two groups of information so that when I update one, the other updates along with it. From my research here at SO, as well as in Google, it appears the general rule of thumb is: "Build the database, and then create your LINQ to SQL classes." Of course, if I make a change in my database, the LINQ to SQL doesn't update automatically and I have to do it by hand. This is fairly simple right now as my database is small, but I am curious if there is an easier way for this to happen. In addition, the LINQ to SQL tool is pretty nice. The ability to create tables, add associations, and even create inheritance is very simple. As my second question, I am curious as to whether or not VS2010 can work the other way - I design the database in the DBLM file and then link it back to my database project. I appreciate any help with either of these two questions. I'm really interested in making this as easy as possible to reduce errors during development and improve the speed at which changes can be made.

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• VB6 ImageList Frm Code Generation

  - by DAC

  Note: This is probably a shot in the dark, and its purely out of curiosity that I'm asking. When using the ImageList control from the Microsoft Common Control lib (mscomctl.ocx) I have found that VB6 generates FRM code that doesn't resolve to real property/method names and I am curious as to how the resolution is made. An example of the generated FRM code is given below with an ImageList containing 3 images: Begin MSComctlLib.ImageList ImageList1 BackColor = -2147483643 ImageWidth = 100 ImageHeight = 45 MaskColor = 12632256 BeginProperty Images {2C247F25-8591-11D1-B16A-00C0F0283628} NumListImages = 3 BeginProperty ListImage1 {2C247F27-8591-11D1-B16A-00C0F0283628} Picture = "Form1.frx":0054 Key = "" EndProperty BeginProperty ListImage2 {2C247F27-8591-11D1-B16A-00C0F0283628} Picture = "Form1.frx":3562 Key = "" EndProperty BeginProperty ListImage3 {2C247F27-8591-11D1-B16A-00C0F0283628} Picture = "Form1.frx":6A70 Key = "" EndProperty EndProperty End From my experience, a BeginProperty tag typically means a compound property (an object) is being assigned to, such as the Font object of most controls, for example: Begin VB.Form Form1 Caption = "Form1" ClientHeight = 10950 ClientLeft = 60 ClientTop = 450 ClientWidth = 7215 BeginProperty Font Name = "MS Serif" Size = 8.25 Charset = 0 Weight = 400 Underline = 0 'False Italic = -1 'True Strikethrough = 0 'False EndProperty End Which can be easily seen to resolve to VB.Form.Font.<Property Name>. With ImageList, there is no property called Images. The GUID associated with property Images indicates type ListImages which implements interface IImages. This type makes sense, as the ImageList control has a property called ListImages which is of type IImages. Secondly, properties ListImage1, ListImage2 and ListImage3 don't exist on type IImages, but the GUID associated with these properties indicates type ListImage which implements interface IImage. This type also makes sense, as IImages is in fact a collection of IImage. What doesn't make sense to me is how VB6 makes these associations. How does VB6 know to make the association between the name Images - ListImages purely because of an associated type (provided by the GUID) - perhaps because it's the only property of that type? Secondly, how does it resolve ListImage1, ListImage2 and ListImage3 into additions to the collection IImages, and does it use the Add method? Or perhaps the ControlDefault property? Perhaps VB6 has specific knowledge of this control and no logical resolution exists?

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• Rails Counter Cache and its implementation

  - by Ishu

  Hello All, I am trying to get hold of rails counter cache feature but not able to grasp it completely. Let's say that We have 3 models A B C A belongs to B or C depending upon a field key_type and key_id. key_type tells whether A belongs to B or C so if key_type="B" then the record belongs to B otherwise it belongs to C. In my model a.rb, I have defined following associations: belongs_to :b, :counter_cache => true, :foreign_key => "key_id" belongs_to :c, :counter_cache => true, :foreign_key => "key_id" and in b and c model files has_many :as , :conditions => {:key_type => "B"} has_many :as , :conditions => {:key_type => "C"} Both B and C Models have a column as as_count The problem is every time an object of a is created count is increased in the both the models b and c. Any help is appreciated. Initially i thought that this may work: belongs_to :b, :counter_cache => true, :foreign_key => "key_id", :conditions => {:key_type => "B"} belongs_to :c, :counter_cache => true, :foreign_key => "key_id", :conditions => {:key_type => "C"} But this does not help. Thanks

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• cache_money only writing to memcached on creates and updates, and seemingly never looking in the cac

  - by Shane Liebling

  I seem to be having some extremely odd cache_money interactions. When I am on the console, and I create a new instance of a class and save it I see the cache misses and cache stores on my memcached console output. Then when the create finishes I see a bunch of cache deletions. If I then try to do any kind of find for the newly created object (or any other objects for that matter) I never see any cache access. This is highly confusing. I could kind of understand if all finds never hit the cache (though that in and of itself would be an issue requiring investigation), but finds do seem to hit the cache when the object is being created (checking for associations and such). Anyone have this experience in the past at all? Any thoughts? AFAIK there isn't really much in the way of configuration options for cache_money, and it certainly doesn't seem like there are any that would be on by default and be creating these kinds of symptoms. My cache_money config is basically straight out of the docs. Any help would be greatly appreciated.

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• Lazy Loading Association and Casting

  - by Zuber

  I am using NHibernate 2.0.1 and .NET I am facing issues with Lazy loading an association I have a BusinessObject class that has associations to other BusinessObject in it, and it can go deeper. The following function is in the BusinessObject to read the values of a collection in the BusinessObject. public virtual object GetFieldValue(string fieldName) { var fieldItems = fieldName.Split(AppConstants.DotChar); var objectToRead = this; for (var i = 0; i < fieldItems.Length - 1; i++) { objectToRead = (BusinessObject) objectToRead.GetFieldValue(fieldItems[i]); } //if (objectToRead._data == null) return objectToRead.SystemId + " Error: _data was null"; return objectToRead.FieldValue(fieldName.LastItem()); } The FieldValue function is described below private object FieldValue(string fieldName) { return _data.Contains(fieldName) ? _data[fieldName] : null; } The BusinessObject has a dictionary_data which stores the field values. Assume the fieldName is BusinessDriver.Description and the BusinessObject which has this field is StrategyBusinessDriver This code breaks down the field name into two - BusinessDriver & Description. The first iteration reads the BusinessDriver object from StrategyBusinessDriver. It is cast into a BusinessObject type so that I can call the GetFieldValue again on it to read the next field i.e Description in the BusinessDriver. The problem is that when I read the BusinessDriver in the first iteration and cast it, I get the Ids and all other details of the BusinessObject but the field dictionary _data and other collections are not fetched. This should be fetched lazily when I read the _data of the BusinessObject. However, this does not happen and I get an error that _data is null. Is there something wrongly coded because of which the collection is not fetched lazily? Please ask for more clarifications if needed. Thanks in advance. UPDATE: It works when I don't do Lazy load.

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• nhibernate many to many deletes

  - by asi farran

  I have 2 classes that have a many to many relationship. What i'd like to happen is that whenever i delete one side ONLY the association records will be deleted with no concern which side i delete. simplified model: classes: class Qualification { IList<ProfessionalListing> ProfessionalListings } class ProfessionalListing { IList<Qualification> Qualifications void AddQualification(Qualification qualification) { Qualifications.Add(qualification); qualification.ProfessionalListings.Add(this); } } fluent automapping with overrides: void Override(AutoMapping<Qualification> mapping) { mapping.HasManyToMany(x => x.ProfessionalListings).Inverse(); } void Override(AutoMapping<ProfessionalListing> mapping) { mapping.HasManyToMany(x => x.Qualifications).Not.LazyLoad(); } I'm trying various combinations of cascade and inverse settings but can never get there. If i have no cascades and no inverse i get duplicated entities in my collections. Setting inverse on one side makes the duplication go away but when i try to delete a qualification i get a 'deleted object would be re-saved by cascade'. How do i do this? Should i be responsible for clearing the associations of each object i delete?

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• traversal of multiple separate web services in a ring network

  - by qkrsppopcmpt

  I am facing a design problem, here is some basic requirement: Aggregator 1. Separate service for blog,video,images and associations. 2. Each of the service should be completely separate, that means they run on separate tomcat. 3. And each aggregator must be able to query local database and other aggregators 4. Traversal of services must be asynchronous using a ring network. For example, we have a ring like ws1-ws2-ws3-ws4-ws1. Each node represents one type of one aggregator. The traveral goes in this way: the query from ws1 to ws2, and ws1 is waiting for the response from ws2 asynchronously; ws2 to ws3, also ws2 wait for ws3 asynchronously. If ws3 has the data, reply to ws2 then to ws1, then reply. However if ws3 goes away, the traversal should go back to ws2, then to ws1, then go to ws4, then go to ws3 again. then tells ws4 since ws3 fails. The required technology is axis2 and tomcat 6. Does anybody have any clue about it? If it is clear, I can clarify the question more clearly. Thanks very much.

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• Should the entity framework + self tracking entities be saving me time

  - by sipwiz

  I've been using the entity framework in combination with the self tracking entity code generation templates for my latest silverlight to WCF application. It's the first time I've used the entity framework in a real project and my hope was that I would save myself a lot of time and effort by being able to automatically update the whole data access layer of my project when my database schema changed. Happily I've found that to be the case, updating my database schema by adding a new table, changing column names, adding new columns etc. etc. can be propagated to my business object classes by using the update from database option on the entity framework model. Where I'm hurting is the CRUD operations within my WCF service in response to actions on my Silverlight client. I use the same self tracking entity framework business objects in my Silverlight app but I find I'm continually having to fight against problems such as foreign key associations not being handled correctly when updating an object or the change tracker getting confused about the state of an object at the Silverlight end and the data access operation within the WCF layer throwing a wobbly. It's got to a point where I have now spent more time dealing with this quirks than I have on my previous project where I used Linq-to-SQL as the starting point for rolling my own business objects. Is it just me being hopeless or is the self tracking entities approach something that should be avoided until it's more mature?

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• Non Working Relationship

  - by Dominik K.

  Hello everyone, I got a problem with cake's model architecture. I got a Users-Model and a Metas-Model. Here are the model codes: Users: <?php class User extends AppModel { var $name = 'User'; var $validate = array( 'username' => array('notempty'), 'email' => array('email'), 'password' => array('notempty') ); var $displayField = 'username'; var $hasMany = array( 'Meta' => array( 'className' => 'Meta', 'foreignKey' => 'user_id' ) ); } ?> and the Metas Model: <?php class Meta extends AppModel { var $name = 'Meta'; //The Associations below have been created with all possible keys, those that are not needed can be removed var $belongsTo = array( 'User' => array( 'className' => 'User', 'foreignKey' => 'user_id', 'required' => true ) ); } ?> So now the question is why do I not get the Meta data into the User array? Should I get it in the Auth object? Or where can I work with the meta data? hope you can help me! Have a nice Day! Dom

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• accepts_nested_attributes_for and nested_form plugin

  - by Denis

  Hi folks, I've the following code in a _form.html.haml partial, it's used for new and edit actions. (fyi I use the Ryan Bates' plugin nested_form) .fields - f.fields_for :transportations do |builder| = builder.collection_select :person_id, @people, :id, :name, {:multiple => true} = builder.link_to_remove 'effacer' = f.link_to_add "ajouter", :transportations works fine for the new action... for the edit action, as explain in the doc, I've to add the :id of already existing associations, so, I've to add something like = builder.hidden_field :id, ?the value? if ?.new_record? How can I get the value? Here is the doc of accepts_nested_attributes_for for reference (source: http://github.com/rails/rails/blob/master/activerecord/lib/active_record/nested_attributes.rb#L332) # Assigns the given attributes to the collection association. # # Hashes with an <tt>:id</tt> value matching an existing associated record # will update that record. Hashes without an <tt>:id</tt> value will build # a new record for the association. Hashes with a matching <tt>:id</tt> # value and a <tt>:_destroy</tt> key set to a truthy value will mark the # matched record for destruction. # # For example: # # assign_nested_attributes_for_collection_association(:people, { # '1' => { :id => '1', :name => 'Peter' }, # '2' => { :name => 'John' }, # '3' => { :id => '2', :_destroy => true } # }) # # Will update the name of the Person with ID 1, build a new associated # person with the name `John', and mark the associatied Person with ID 2 # for destruction. # # Also accepts an Array of attribute hashes: # # assign_nested_attributes_for_collection_association(:people, [ # { :id => '1', :name => 'Peter' }, # { :name => 'John' }, # { :id => '2', :_destroy => true } # ]) Thanks for your help.

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• Sharepoint BDC Error: The title property of entity tblStaff is set to an invalid value

  - by Christopher Rathermel

  I am just starting to create our Business Data Catalog(s) for our practice management system and I am running into an issue w/ our staff table. Background: I am using Business Data Catalog Definition Editor to create my ADF. I am using the RevertToSelf Authentication Mode. I have tried a few other tables and they seem to work just fine thus far.. only issue is w/ the staff table. If I removed all the columns for the staff entity except the ID and a few columns for the name it actually works. So it has a problem w/ one of my columns in tblStaff. I receive this error even when I set up an ADF w/ just this one entity. So w/ no associations.. When attempting to view the record: http://servername/ssp/admin/Content/tblstaff.aspx?StaffID={0} w/ {0} replaced w/ an actual staff ID I get the following error: The title property of entity tblStaff is set to an invalid value. Things I have tried: I noticed that I do have a column in my staff table called "Title" and removed it from ADF w/ no luck... Same error.. I tried to use bdc meta man to create my ADF and I got the same error... Any ideas? Chris

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• Templates, and C++ operator for logic: B contained by set A

  - by James Morris

  In C++, I'm looking to implement an operator for selecting items in a list (of type B) based upon B being contained entirely within A. In the book "the logical design of digital computers" by Montgomery Phister jr (published 1958), p54, it says: F11 = A + ~B has two interesting and useful associations, neither of them having much to do with computer design. The first is the logical notation of implication... The second is notation of inclusion... This may be expressed by a familiar looking relation, B < A; or by the statement "B is included in A"; or by the boolean equation F11= A + ~B = 1. My initial implementation was in C. Callbacks were given to the list to use for such operations. An example being a list of ints, and a struct containting two ints, min and max, for selection purposes. There, selection would be based upon B = A-min && B <= A-max. Using C++ and templates, how would you approach this after having implemented a generic list in C using void pointers and callbacks? Is using < as an over-ridden operator for such purposes... <ugh> evil? </ugh> (or by using a class B for the selection criteria, implementing the comparison by overloading ?)

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• Virgin STI Help

  - by Mutuelinvestor

  I am working on a horse racing application and I'm trying to utilize STI to model a horse's connections. A horse's connections is comprised of his owner, trainer and jockey. Over time, connections can change for a variety of reasons: The horse is sold to another owner The owner switches trainers or jockey The horse is claimed by a new owner As it stands now, I have model this with the following tables: horses connections (join table) stakeholders (stakeholder has three sub classes: jockey, trainer & owner) Here are my clases and associations: class Horse < ActiveRecord::Base has_one :connection has_one :owner_stakeholder, :through => :connection has_one :jockey_stakeholder, :through => :connection has_one :trainer_stakeholder, :through => :connection end class Connection < ActiveRecord::Base belongs_to :horse belongs_to :owner_stakeholder belongs_to :jockey_stakeholder belongs_to :trainer_stakeholder end class Stakeholder < ActiveRecord::Base has_many :connections has_many :horses, :through => :connections end class Owner < Stakeholder # Owner specific code goes here. end class Jockey < Stakeholder # Jockey specific code goes here. end class Trainer < Stakeholder # Trainer specific code goes here. end One the database end, I have inserted a Type column in the connections table. Have I modeled this correctly. Is there a better/more elegant approach. Thanks in advance for you feedback. Jim

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• How to nest joins with CakePHP?

  - by Daren Thomas

  I'm trying to behave. So, instead of using following SQL syntax: select * from tableA INNER JOIN tableB on tableA.id = tableB.tableA_id LEFT OUTER JOIN ( tableC INNER JOIN tableD on tableC.tableD_id = tableD.id) on tableC.tableA_id = tableA.id I'd like to use the CakePHP model->find(). This will let me use the Paginator too, since that will not work with custom SQL queries as far as I understand (unless you hardcode one single pagination query to the model which seems a little inflexible to me). What I've tried so far: /* inside tableA_controller.php, inside an action, e.g. "view" */ $this->paginate['recursive'] = -1; # suppress model associations for now $this->paginate['joins'] = array( array( 'table' => 'tableB', 'alias' => 'TableB', 'type' => 'inner', 'conditions' => 'TableB.tableA_id = TableA.id', ), array( 'table' => 'tableC', 'alias' => 'TableC', 'type' => 'left', 'conditions' => 'TableC.tableA_id = TableA.id', 'joins' = array( # this would be the obvious way to do it, but doesn't work array( 'table' => 'tableD', 'alias' => 'TableD', 'type' => 'inner', 'conditions' => 'TableC.tableD_id = TableD.id' ) ) ) ) That is, nesting the joins into the structure. But that doesn't work (CakePHP just ignores the nested 'joins' element which was kind of what I expected, but sad. I have seen hints in comments on how to do subqueries (in the where clause) using a statement builder. Can a similar trick be used here?

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• How can I make this method more Scalalicious

  - by Neil Chambers

  I have a function that calculates the left and right node values for some collection of treeNodes given a simple node.id, node.parentId association. It's very simple and works well enough...but, well, I am wondering if there is a more idiomatic approach. Specifically is there a way to track the left/right values without using some externally tracked value but still keep the tasty recursion. /* * A tree node */ case class TreeNode(val id:String, val parentId: String){ var left: Int = 0 var right: Int = 0 } /* * a method to compute the left/right node values */ def walktree(node: TreeNode) = { /* * increment state for the inner function */ var c = 0 /* * A method to set the increment state */ def increment = { c+=1; c } // poo /* * the tasty inner method * treeNodes is a List[TreeNode] */ def walk(node: TreeNode): Unit = { node.left = increment /* * recurse on all direct descendants */ treeNodes filter( _.parentId == node.id) foreach (walk(_)) node.right = increment } walk(node) } walktree(someRootNode) Edit - The list of nodes is taken from a database. Pulling the nodes into a proper tree would take too much time. I am pulling a flat list into memory and all I have is an association via node id's as pertains to parents and children. Adding left/right node values allows me to get a snapshop of all children (and childrens children) with a single SQL query. The calculation needs to run very quickly in order to maintain data integrity should parent-child associations change (which they do very frequently). In addition to using the awesome Scala collections I've also boosted speed by using parallel processing for some pre/post filtering on the tree nodes. I wanted to find a more idiomatic way of tracking the left/right node values. After looking at the answers listed I have settled on this synthesised version: def walktree(node: TreeNode) = { def walk(node: TreeNode, counter: Int): Int = { node.left = counter node.right = treeNodes .filter( _.parentId == node.id) .foldLeft(counter+1) { (counter, curnode) => walk(curnode, counter) + 1 } node.right } walk(node,1) }

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• Having difficulties in ending Michael Hartl's tutorial. Help?

  - by konzepz

  Following Michael Hartl's (amazing) Ruby on Rails Tutorial, on the final section, I get the following errors: 1) User micropost associations status feed should include the microposts of followed users Failure/Error: @user.feed.should include(mp3) expected [#<Micropost id: 2, content: "Foo bar", user_id: 1, created_at: "2011-01-12 21:22:41", updated_at: "2011-01-12 22:22:41">, #<Micropost id: 1, content: "Foo bar", user_id: 1, created_at: "2011-01-11 22:22:41", updated_at: "2011-01-12 22:22:41">] to include #<Micropost id: 3, content: "Foo bar", user_id: 2, created_at: "2011-01-12 22:22:41", updated_at: "2011-01-12 22:22:41"> Diff: @@ -1,2 +1,2 @@ -#<Micropost id: 3, content: "Foo bar", user_id: 2, created_at: "2011-01-12 22:22:41", updated_at: "2011-01-12 22:22:41"> +[#<Micropost id: 2, content: "Foo bar", user_id: 1, created_at: "2011-01-12 21:22:41", updated_at: "2011-01-12 22:22:41">, #<Micropost id: 1, content: "Foo bar", user_id: 1, created_at: "2011-01-11 22:22:41", updated_at: "2011-01-12 22:22:41">] # ./spec/models/user_spec.rb:214 2) Micropost from_users_followed_by should include the followed user's microposts Failure/Error: Micropost.from_users_followed_by(@user).should include(@other_post) expected [#<Micropost id: 1, content: "foo", user_id: 1, created_at: "2011-01-12 22:22:46", updated_at: "2011-01-12 22:22:46">] to include #<Micropost id: 2, content: "bar", user_id: 2, created_at: "2011-01-12 22:22:46", updated_at: "2011-01-12 22:22:46"> Diff: @@ -1,2 +1,2 @@ -#<Micropost id: 2, content: "bar", user_id: 2, created_at: "2011-01-12 22:22:46", updated_at: "2011-01-12 22:22:46"> +[#<Micropost id: 1, content: "foo", user_id: 1, created_at: "2011-01-12 22:22:46", updated_at: "2011-01-12 22:22:46">] # ./spec/models/micropost_spec.rb:75 Finished in 9.18 seconds 153 examples, 2 failures Seems like mp3 is not included in the feed. Any ideas on how to fix it? Or where to look for possible errors in the code? I compared the files with Hartl's original code; seems exact. Thanks.

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• How to restrict text search to a certain subset of the database ?

  - by Nikhil Garg

  I have a large central database of around 1 million heavy records. In my app, for every user I would have a subset of rows from central table, which would be very small (probably 100 records each).When a particular user has logged in , I would want to search on this data set only. Example: Say I have a central database of all cars in the world. I have a user profile for General Motors(GM) , Ferrari etc. When GM is logged in I just want to search(a full text search and not fire a sql query) for those cars which are manufactured by GM. Also GM may launch/withdraw a model in which case central db would be updated & so would be rowset associated with GM. In case of acquisitions, db of certain profiles may change without launch/removal of new car. So central db wont change then , but rowsets may. Whats the best way to implement such a design ? These smaller row sets would need to be dynamic depending on user activities. We are on Rails 2.3.5 and use thinking_sphinx as the connector and Sphinx/MySQL for search and relational associations.

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• How do I model teams and gameplay in this scorekeeping application?

  - by Eric Hill

  I'm writing a scorekeeping application for card game that has a few possibly-interesting constraints. The application accepts user registrations for players, then lets them check-in to a particular game (modeled as Event). After the final player registers, the app should generate teams, singles or doubles, depending on the preference of the person running the game and some validations (can't do doubles if there's an odd number checked in). There are @event.teams.count rounds in the game. To sum up: An event consists of `@event.teams.count` rounds; Teams can have 1 or more players Events have n or n/2 teams (depending on whether it's singles or doubles) Users will be members of different teams at different events Currently I have a rat's nest of associations: class User < ActiveRecord::Base has_many :teams, :through => :players has_many :events, :through => :teams class Event < ActiveRecord::Base has_many :rounds has_many :teams has_many :players, :through => :teams class Player < ActiveRecord::Base belongs_to :user belongs_to :team end class Team < ActiveRecord::Base has_many :players belongs_to :event end class Round < ActiveRecord::Base belongs_to :event belongs_to :user end The sticky part is team generation. I have basically a "start game" button that should freeze the registrations and pair up teams either singly or doubly, and render to Round#new so that the first (and subsequent) matches can be scored. Currently I'm implementing this as a check on Round#new that calls Event#generate_teams and displays the view: # Event#generate_teams def generate_teams # User has_many :events, :through => :registrations # self.doubles is a boolean denoting 2 players per team registrations.in_groups_of(self.doubles ? 2 : 1, nil).each do |side| self.teams << Player.create(self,side) end end Which doesn't work. Should there maybe be a Game model that ties everything together rather than (my current method) defining the game as an abstraction via the relationships between Events, Users, and Rounds (and Teams and Players and etc.)? My head is swimming.

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• Avoiding secondary selects or joins with Hibernate Criteria or HQL query

  - by Ben Benson

  I am having trouble optimizing Hibernate queries to avoid performing joins or secondary selects. When a Hibernate query is performed (criteria or hql), such as the following: return getSession().createQuery(("from GiftCard as card where card.recipientNotificationRequested=1").list(); ... and the where clause examines properties that do not require any joins with other tables... but Hibernate still performs a full join with other tables (or secondary selects depending on how I set the fetchMode). The object in question (GiftCard) has a couple ManyToOne associations that I would prefer to be lazily loaded in this case (but not necessarily all cases). I want a solution that I can control what is lazily loaded when I perform the query. Here's what the GiftCard Entity looks like: @Entity @Table(name = "giftCards") public class GiftCard implements Serializable { private static final long serialVersionUID = 1L; private String id_; private User buyer_; private boolean isRecipientNotificationRequested_; @Id public String getId() { return this.id_; } public void setId(String id) { this.id_ = id; } @ManyToOne @JoinColumn(name = "buyerUserId") @NotFound(action = NotFoundAction.IGNORE) public User getBuyer() { return this.buyer_; } public void setBuyer(User buyer) { this.buyer_ = buyer; } @Column(name="isRecipientNotificationRequested", nullable=false, columnDefinition="tinyint") public boolean isRecipientNotificationRequested() { return this.isRecipientNotificationRequested_; } public void setRecipientNotificationRequested(boolean isRecipientNotificationRequested) { this.isRecipientNotificationRequested_ = isRecipientNotificationRequested; } }

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• Understanding Domain Driven Design

  - by Nihilist

  Hi I have been trying to understand DDD for few weeks now. Its very confusing. I dont understand how I organise my projects. I have lot of questions on UnitOfWork, Repository, Associations and the list goes on... Lets take a simple example. Album and Tracks. Album: AlbumId, Name, ListOf Tracks Tracks: TrackId, Name Question1: Should i expose Tracks as a IList/IEnumerabe property on Album ? If that how do i add an album ? OR should i expose a ReadOnlyCollection of Tracks and expose a AddTrack method? Question2: How do i load Tracks for Album [assuming lazy loading]? should the getter check for null and then use a repository to load the tracks if need be? Question3: How do we organise the assemblies. Like what does each assembly have? Model.dll - does it only have the domain entities? Where do the repositories go? Interfaces and implementations both. Can i define IAlbumRepository in Model.dll? Infrastructure.dll : what shold this have? Question4: Where is unit of work defined? How do repository and unit of work communicate? [ or should they ] for example. if i need to add multiple tracks to album, again should this be defined as AddTrack on Album OR should there a method in the repository? Regardless of where the method is, how do I implement unit of work here? Question5: Should the UI use Infrastructure..dll or should there be ServiceLayer? Do my quesitons make sense? Regards

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• Many to many table design question

  - by user169867

  Originally I had 2 tables in my DB, [Property] and [Employee]. Each employee can have 1 "Home Property" so the employee table has a HomePropertyID FK field to Property. Later I needed to model the situation where despite having only 1 "Home Property" the employee did work at or cover for multiple properties. So I created an [Employee2Property] table that has EmployeeID and PropertyID FK fields to model this many 2 many relationship. Now I find that I need to create other many-to-many relationships between employees and properties. For example if there are multiple employees that are managers for a property or multiple employees that perform maintenance work at a property, etc. My questions are: 1) Should I create seperate many-to-many tables for each of these situations or should I just create 1 more table like [PropertyAssociatonType] that lists the types of associations an emploee can have with a property and just add a FK field to [Employee2Property] such a PropertyAssociationTypeID that explains what the association is? I'm curious about the pros/cons or if there's another better way. 2) Am I stupid and going about this all worng? Thanks for any suggestions :)

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• Delete element from Set

  - by Blitzkr1eg

  Hi. I have 2 classes Tema(Homework) and Disciplina (course), where a Course has a Set of homeworks. In Hibernate i have mapped this to a one-to-many associations like this: <class name="model.Disciplina" table="devgar_scoala.discipline" > <id name="id" > <generator class="increment"/> </id> <set name="listaTeme" table="devgar_scoala.teme"> <key column="Discipline_id" not-null="true" ></key> <one-to-many class="model.Tema" ></one-to-many> </set> </class> <class name="model.Tema" table="devgar_scoala.teme" > <id name="id"> <generator class="increment" /> </id> <property name="titlu" type="string" /> <property name="cerinta" type="binary"> <column name="cerinta" sql-type="blob" /> </property> </class> The problem is that it will add (insert rows in the table 'Teme') but it won't delete any rows and i get no exceptions thrown. Im using the merge() method.

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