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• Creating relationship between two model instances

  - by Lowgain

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

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• Where to start when doing a Domain Model?

  - by devoured elysium

  Let's say I've made a list of concepts I'll use to draw my Domain Model. Furthermore, I have a couple of Use Cases from which I did a couple of System Sequence Diagrams. When drawing the Domain Model, I never know where to start from: Designing the model as I believe the system to be. This is, if I am modelling a the human body, I start by adding the class concepts of Heart, Brain, Bowels, Stomach, Eyes, Head, etc. Start by designing what the Use Cases need to get done. This is, if I have a Use Case which is about making the human body swallow something, I'd first draw the class concepts for Mouth, Throat, Stomatch, Bowels, etc. The order in which I do things is irrelevant? I'd say probably it'd be best to try to design from the Use Case concepts, as they are generally what you want to work with, not other kind of concepts that although help describe the whole system well, much of the time might not even be needed for the current project. Is there any other approach that I am not taking in consideration here? How do you usually approach this? Thanks

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• When should I use a struct instead of a class?

  - by Esteban Araya

  MSDN says that you should use structs when you need lightweight objects. Are there any other scenarios when a struct is preferable over a class? Edit: Some people have forgotten that: 1. structs can have methods! 2. structs have no inheritance capabilites. Another Edit: I understand the technical differences, I just don't have a good feel for WHEN to use a struct.

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• What's the recommended way to declare fields of a class in JavaScript?

  - by Bytecode Ninja

  Is it better to declare fields of a class in this way: function MyClass() { this.aMethod = function() { // code } } Or this way: function MyClass() { } MyClass.prototype.aMethod = function() { // code } Any why? Thanks in advance.

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• How to properly name classes inside a domain namespace?

  - by devoured elysium

  Let's say I'm trying to implement a Chess Game. I'd create my Chess classes in a Chess namespace. Now, should I prefix all my Chess related classes with the Chess word, or as they are already inside that namespace, should I just call them by what they are? Example: ChessGame vs Game ChessPiece vs Piece

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• In Drools Rules, how to use two different ArrayList objects,obj1 is used in rule 1 and obj2 used in rule2?

  - by Jenn

  I am doing ksession.insert(list) and after that I have to fire rule 1 in the drl file, then ksession.insert(list) and fire rule 2 in the drl. Could someone tell me how to achieve this. I read about agenda filters and facthandles but do not really know how to get this to work Below is some code: ArrayList list = new ArrayList(); list.add(product1); list.add(product2); list.add(product3); ksession.insert(list); ksession.fireAllRules("fire rule 1 in drl"); //remove list? ArrayList list2 = new ArrayList(); list2.add(str1); list2.add(str2); list2.add(str3); ksession.insert(list2); ksession.fireAllRules("fire rule 2 in drl");

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• Free object/widget in GTK?

  - by wag2639

  I've got a pack box in my GTK application and I'm replacing it every once in a while with a completely new entry (at least for now cause I'm in a hurry). Since I'm replacing it with a new instance, do I need to explicitly free from memory the old pack box contents or is there some garbage collection in GTK? If I do need to explicitly need to free the object, is there a command that will recursively go to all objects in that tree (like will it clear my button in a box container inside my main pack box)? I'm using C/GTK-2.0 (gcc v4.4.3 and GTK 2.20.0).

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• Compromising design & code quality to integrate with existing modules

  - by filip-fku

  Greetings! I inherited a C#.NET application I have been extending and improving for a while now. Overall it was obviously a rush-job (or whoever wrote it was seemingly less competent than myself). The app pulls some data from an embedded device & displays and manipulates it. At the core is a communications thread in the main application form which executes a 600+ lines of code method which calls functions all over the place, implementing a state machine - lots of if-state-then-do type code. Interaction with the device is done by setting the state/mode globally and letting the thread do it's thing. (This is just one example of the badness of the code - overall it is not very OO-like, it reminds of the style of embedded C code the device firmware is written in). My problem is that this piece of code is central to the application. The software, communications protocol or device firmware are not documented at all. Obviously to carry on with my work I have to interact with this code. What I would like some guidance on, is whether it is worth scrapping this code & trying to piece together something more reasonable from the information I can reverse engineer? I can't decide! The reason I don't want to refactor is because the code already works, and changing it will surely be a long, laborious and unpleasant task. On the flip side, not refactoring means I have to sometimes compromise the design of other modules so that I may call my code from this state machine! I've heard of "If it ain't broke don't fix it!", so I am wondering if it should apply when "it" is influencing the design of future code! Any advice would be appreciated! Thanks!

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• Custom link on embedded youtube video

  - by 0plus1

  I'm looking to direct the user on the channell webpage instead of the video url that I'm embedding. I've read the api and I didn't see any way to achieve this. I tried enclosing the embedded video in a and I added this code: $('#youtube').click(function() { document.write('http://www.youtube.com/user/trasportareoggi'); return false; }); And surprise it won't work. How, if it's even possible I can do this?

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• How to add an additional field to a queryset?

  - by Mark

  I've got a list of affiliates (users who have referred someone to the site): affiliates = User.objects.annotate(referral_count=Count('referrals')).filter(referral_count__gt=0) And a count of the number of users each affiliate has referred within a time frame: new_users = User.objects.filter(date_joined__gt=sd, date_joined__lte=ed) new_referrals = User.objects.filter(referrals__user__in=new_users).annotate(referral_count=Count('referrals')) How can I do something like new_referrals['affiliate.username'].referral_count from within my template? Note that this is not just a syntax issue, I also need to index new_referrals somehow so that I'm able to do this. Either this, or if I can somehow add a new_referral_count to the first query, that'd work too.

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• Designing a chain of states

  - by devoured elysium

  I want to model a kind of FSM(Finite State Machine). I have a sequence of states (let's say, from StateA to StateZ). This sequence is called a Chain and is implemented internally as a List. I will add states by the order I want them to run. My purpose is to be able to make a sequence of actions in my computer (for example, mouse clicks). (I know this has been done a zillion times). So a state is defined as a: boolean Precondition() <- Checks to see if for this state, some condition is true. For example, if I want to click in the Record button of a program, in this method I would check if the program's process is running or not. If it is, go to the next state in the chain list, otherwise, go to what was defined as the fail state (generally is the first state of them all). IState GetNextState() <- Returns the next state to evaluate. If Precondition() was sucessful, it should yield the next state in the chain otherwise it should yield the fail state. Run() Simply checks the Precondition() and sets the internal data so GetNextState() works as expected. So, a naive approach to this would be something like this: Chain chain = new Chain(); //chain.AddState(new State(Precondition, FailState, NextState) <- Method structure chain.AddState(new State(new WinampIsOpenCondition(), null, new <problem here, I want to referr to a state that still wasn't defined!>); The big problem is that I want to make a reference to a State that at this point still wasn't defined. I could circumvent the problem by using strings when refrering to states and using an internal hashtable, but isn't there a clearer alternative? I could just pass only the pre-condition and failure states in the constructor, having the chain just before execution put in each state the correct next state in a public property but that seems kind of awkward.

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• Modules vs. Classes and their influence on descendants of ActiveRecord::Base

  - by Chris

  Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario: class Product < ActiveRecord::Base has_many(:prices) # define private helper methods end module PrintProduct attr_accessor(:isbn) # override methods in ActiveRecord::Base end class Book < Product include PrintProduct end Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior: After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found. Why is that? Book is a direct descendant of Product! More interesting is the following.. As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such: class Product < ActiveRecord::Base end class PrintProduct < Product end class Book < PrintProduct end All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module. Any insight would be appreciated. I'm dying to know why these errors are occurring!

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• Hibernate - EhCache - Which region to Cache associations/sets/collections ??

  - by lifeisnotfair

  Hi all, I am a newcomer to hibernate. It would be great if someone could comment over the following query that i have: Say i have a parent class and each parent has multiple children. So the mapping file of parent class would be something like: parent.hbm.xml <hibernate-mapping > <class name="org.demo.parent" table="parent" lazy="true"> <cache usage="read-write" region="org.demo.parent"/> <id name="id" column="id" type="integer" length="10"> <generator class="native"> </generator> </id> <property name="name" column="name" type="string" length="50"/> <set name="children" lazy="true"> <cache usage="read-write" region="org.demo.parent.children" /> <key column="parent_id"/> <one-to-many class="org.demo.children"/> </set> </class> </hibernate-mapping> children.hbm.xml <hibernate-mapping > <class name="org.demo.children" table="children" lazy="true"> <cache usage="read-write" region="org.demo.children"/> <id name="id" column="id" type="integer" length="10"> <generator class="native"> </generator> </id> <property name="name" column="name" type="string" length="50"/> <many-to-one name="parent_id" column="parent_id" type="integer" length="10" not-null="true"/> </class> </hibernate-mapping> So for the set children, should we specify the region org.demo.parent.children where it should cache the association or should we use the cache region of org.demo.children where the children would be getting cached. I am using EHCache as the 2nd level cache provider. I tried to search for the answer to this question but couldnt find any answer in this direction. It makes more sense to use org.demo.children but I dont know in which scenarios one should use a separate cache region for associations/sets/collections as in the above case. Kindly provide your inputs also let me know if I am not clear in my question. Thanks all.

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• Rowwise iteration of a dictionay object

  - by mono

  I have a dictionary object like: Dictionary<string, HashSet<int>> dict = new Dictionary<string, HashSet<int>>(); dict.Add("foo", new HashSet<int>() { 15,12,16,18}); dict.Add("boo", new HashSet<int>() { 16,47,45,21 }); I have to print in such a way such that result would be as following at each iteration: It1: foo boo //only the key in a row It2: 15 16 It3: 16 47 Can anyone help me to achieve this. Thanks.

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• Inheritence and usage of dynamic_cast

  - by Mewzer

  Hello, Suppose I have 3 classes as follows (as this is an example, it will not compile!): class Base { public: Base(){} virtual ~Base(){} virtual void DoSomething() = 0; virtual void DoSomethingElse() = 0; }; class Derived1 { public: Derived1(){} virtual ~Derived1(){} virtual void DoSomething(){ ... } virtual void DoSomethingElse(){ ... } virtual void SpecialD1DoSomething{ ... } }; class Derived2 { public: Derived2(){} virtual ~Derived2(){} virtual void DoSomething(){ ... } virtual void DoSomethingElse(){ ... } virtual void SpecialD2DoSomething{ ... } }; I want to create an instance of Derived1 or Derived2 depending on some setting that is not available until run-time. As I cannot determine the derived type until run-time, then do you think the following is bad practice?... class X { public: .... void GetConfigurationValue() { .... // Get configuration setting, I need a "Derived1" b = new Derived1(); // Now I want to call the special DoSomething for Derived1 (dynamic_cast<Derived1*>(b))->SpecialD1DoSomething(); } private: Base* b; }; I have generally read that usage of dynamic_cast is bad, but as I said, I don't know which type to create until run-time. Please help!

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• JPA query many to one association

  - by Random Joe

  I want to build the following pseudo query Select a From APDU a where a.group.id= :id group is a field in APDU class of the type APDUGroup.class. I just want to get a list of APDUs based on APDUGroup's id. How do i do that using a standard JPA query?

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• Replace singletons with what?

  - by fig-gnuton

  Singletons are so often said to be a bad design choice, so how should you design an application when you want to avoid them?

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• Handling Timeouts In A Website SQLCommand Object and c#

  - by user341684

  I'm using visual studio 2008 and sql server 2005 and everything is working just fine under normal use. However if a user is on a page for a while several minutes with no activity then clicks a button on occassion the site throws the following exception ... Procedure or Function "sp_name" parameter '@SomeParameterName', which was not supplied I'm also encountering this error in Visual Studio while debugging the application, in otherwords run the site from visual studio then make some change to the html in VS save the changes and refresh the page. The error is not consistent nor is the time the page has to stay idle in order for it to occur.... The current sql command object timeout is 30 secs and the website timeout is 30 minutes. Has anyone else experienced this scenario and what is the fix as I would not except anything to go out of scope until the website timeout occurs ... Any insight will be appreciated.

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• rails: has_many :through + polymorphism validation?

  - by ramonrails

  I am trying to achieve this. Any hints? A project has many users through join model A user has many projects through join model Admin class inherits User class. It also has some Admin specific stuff. Admin like inheritance for Supervisor and Operator Project has one Admin, One supervisor and many operators. Now I want to 1. submit data for project, admin, supervisor and operator in a single project form 2. validate all and show errors on the project form. Project has_many :users, :through = :projects_users User has_many :projects, :through = :projects_users ProjectsUser = :id integer, :user_id :integer, :project_id :integer, :user_type :string ProjectUser belongs_to :project, belongs_to :user, :polymorphic = true Admin < User Supervisor < User Operator < User Is the approach correct? Any and all suggestions are welcome.

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• Forcing a templated object to construct from a pointer

  - by SalamiArmi

  I have a fictional class: template<typename T> class demonstration { public: demonstration(){} ... T *m_data; } At some point in the program's execution, I want to set m_data to a big block of allocated memory and construct an object T there. At the moment, I've been using this code: void construct() { *m_data = T(); } Which I've now realised is probably not the best idea... wont work under certain cirumstances, if T has a private assignment operator for example. Is there a normal/better way to do what I'm attempting here?

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• Stupid java question: Is it a method?

  - by Stefan

  Hello, I'm no Java guy, so I ask myself what this means: public Button(Light light) { this.light = light; } Is Button a method? I ask myself, because it takes an input parameter light. But if it was a method, why would it begin with a capital letter and has no return data type? Here comes the full example: public class Button { private Light light; public Button(Light light) { this.light = light; } public void press() { light.turnOn(); } } I know, this question is really trivial. However, I have nothing to do with Java and haven't found a description for the Button thing above. I'm just interested.

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• Using DAO's or static methods in Domain Object with nHibernate

  - by mickyjtwin

  I am using nHibernate for the first time, and after alot of reading/researching, plus looking at other projects done with nHibernate, have seen a couple of implementation practices. I am looking for opinions about which would be best to use and why. Essentially the two methods are as follows: Using Data Access Objects and a DAO Factory. Example usage: INotificationListDAO nListDAO = NHDaoFactory.GetNotificationListDAO(); NotificationList list = nListDAO.GetByListID(""); Use Static methods in the Domain Object. Example usage: NotificationList list = NotificationList.GetByListID(""); NHHelper.Session.Get(id); NHHelper.Session basically calls the NHibernateSessionManager.Instace.GetSessionFrom(""). While both look similar, it is more to do with best practice. From what I understand, the first option is more so if you are developing enterprise level applications, where my requirements are more for mid-range websites.

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• @Transient property should be added in equals/hashCode/toString

  - by Castanho

  Hi there, this is a quick question........... In objects from JPA that is mapping a table, I have some properties that is @Transient, shall I add this properties into equals/hashCode/toString methods? My first thought is NO but.... I don't know why. Tips? Ideas? Explanations? Thanks in advance

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• Passing a string when starting a class in PHP

  - by Francesc

  Hi. First I have to say: Happy Christmas to All! I'm starting learning classes in PHP. I coded that: class User { function getFbId($authtoken) { } function getFbFirstName ($authtoken) { } } What I want to do is something like that: $user=new User($authtoken); And pass the $authtoken to the class. It's possible to define that when starting the class. It's possible to retrive that value inside a function of that class?

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• When to define SDD operations System->Actor?

  - by devoured elysium

  I am having some trouble understanding how to make SDDs, as I don't fully grasp why in some cases one should define operations for System - Actor and in others don't. Here is an example: 1) The User tells the System that wants to buy some tickets, stating his client number. 2) The System confirms that the given client number is valid. 3) The User tells the System the movie that wants to see. 4) The System shows the set of available sessions and seats for that movie. 5) The System asks the user which session/seat he wants. 6) The user tells the System the chosen session/seat. This would be converted to: a) -----> tellClientNumber(clientNumber) b) <----- validClientNumber c) -----> tellMovieToSee(movie) d) <----- showsAvailableSeatsHours e) -----> tellSystemChosenSessionSeat(session, seat) I know that when we are dealing with SDD's we are still far away from coding. But I can't help trying to imagine how it how it would have been had I to convert it right away to code: I can understand 1) and 2). It's like if it was a C#/Java method with the following signature: boolean tellClientNumber(clientNumber) so I put both on the SDD. Then, we have the pair 3) 4). I can imagine that as something as: SomeDataStructureThatHoldsAvailableSessionsSeats tellSystemMovieToSee(movie) Now, the problem: From what I've come to understand, my lecturer says that we shouldn't make an operation on the SDD for 5) as we should only show operations from the Actor to the System and when the System is either presenting us data (as in c)) or validating sent data (such as in b)). I find this odd, as if I try to imagine this like a DOS app where you have to put your input sequencially, it makes sense to make an arrow even for 5). Why is this wrong? How should I try to visualize this? Thanks

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