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• Interacting With Class Objects in Ruby

  - by michaelmichael

  How can I interact with objects I've created based on their given attributes in Ruby? To give some context, I'm parsing a text file that might have several hundred entries like the following: ASIN: B00137RNIQ -------------------------Status Info------------------------- Upload created: 2010-04-09 09:33:45 Upload state: Imported Upload state id: 3 I can parse the above with regular expressions and use the data to create new objects in a "Product" class: class Product attr_reader :asin, :creation_date, :upload_state, :upload_state_id def initialize(asin, creation_date, upload_state, upload_state_id) @asin = asin @creation_date = creation_date @upload_state = upload_state @upload_state_id = upload_state_id end end After parsing, the raw text from above will be stored in an object that look like this: [#<Product:0x00000101006ef8 @asin="B00137RNIQ", @creation_date="2010-04-09 09:33:45 ", @upload_state="Imported ", @upload_state_id="3">] How can I then interact with the newly created class objects? For example, how might I pull all the creation dates for objects with an upload_state_id of 3? I get the feeling I'm going to have to write class methods, but I'm a bit stuck on where to start.

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• .NET | Persist multiple objects in minimum number of queries

  - by VarunGupta

  I have a list of objects which needs to be persisted in a SQL Server database table, where each object gets persisted as single record. i.e. List of objects result in insertion of multiple records. Trivial way of saving the objects is to loop over the list and fire a query/stored procedure/etc. for saving that record. But this results in multiple database interactions. Is there a way to persist the list of objects in lesser number of database interactions?

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• Good design of mapping Java Domain objects to Tables (using Hibernate)

  - by M. McKenzie

  Hey guys, I have a question that is more in the realm of design, than implementation. I'm also happy for anyone to point out resources for the answer and I'll gladly, research for myself. Highly simplified Java and SQL: Say I have a business domain POJO called 'Picture' with three attributes. class Picture int idPicture String fileName long size Say I have another business domain POJO called "Item" with 3 attributes Class Item int idItem String itemName ArrayList itemPictures These would be a normal simple relationship. You could say that 'Picture' object, will never exist outside an 'Item' object. Assume a picture belongs only to a specific item, but that an item can have multiple pictures Now - using good database design (3rd Normal Form), we know that we should put items and pictures in their own tables. Here is what I assume would be correct. table Item int idItem (primary key) String itemName table Picture int idPicture (primary key) varchar(45) fileName long size int idItem (foreign key) Here is my question: If you are making Hibernate mapping files for these objects. In the data design, your Picture table needs a column to refer to the Item, so that a foreign key relation can be maintained. However,in your business domain objects - your Picture does not hold a reference/attribute to the idItem - and does not need to know it. A java Picture instance is always instantiated inside an Item instance. If you want to know the Item that the Picture belongs to you are already in the correct scope. Call myItem.getIdItem() and myItem.getItemPictures(),and you have the two pieces of information you need. I know that Hibernate tools have a generator that can auto make your POJO's from looking at your database. My problem stems from the fact that I planned out the data design for this experiment/project first. Then when I went to make the domain java objects, I realized that good design dictated that the objects hold other objects in a nested way. This is obviously different from the way that a database schema is - where all objects(tables) are flat and hold no other complex types within them. What is a good way to reconcile this? Would you: (A) Make the hibernate mapping files so that Picture.hbm.xml has a mapping to the POJO parent's idItem Field (if it's even possible) (B) Add an int attribute in the Picture class to refer to the idItem and set it at instantiation, thus simplifying the hbm.xml mapping file by having all table fields as local attributes in the class (C) Fix the database design because it is wrong, dork. I'd truly appreciate any feedback

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• Moving 2d objects on a 3d plane - AS3

  - by Borkz

  I have a 2d plane rotated on its x axis, with 2d display objects I want to move around on the plane. Its pretty similar to a chess board: http://static.open.salon.com/files/chess011237853612.jpg The board is a rotated rectangle, and the pieces are just 2d display objects. Whats the easiest way to manipulate those objects so they appear to be moving on the board?

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• Struts:JSON:return multiple objects

  - by cp

  Hello Is it possible to return multiple JSON objects in the request header with Struts1? I am presently returning a single JSON objects, however the need now is to return a second data structure. All the client-side processing works perfectly for the single data structure in the single JSON objects, I really do not want to complicate it by putting two hetrogenous data structures in a single return JSON object. tia.

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• Robust way to save/load objects with dependencies?

  - by mrteacup

  I'm writing an Android game in Java and I need a robust way to save and load application state quickly. The question seems to apply to most OO languages. To understand what I need to save: I'm using a Strategy pattern to control my game entities. The idea is I have a very general Entity class which e.g. stores the location of a bullet/player/enemy and I then attach a Behaviour class that tells the entity how to act: class Entiy { float x; float y; Behavior b; } abstract class Behavior { void update(Entity e); {} // Move about at a constant speed class MoveBehavior extends Behavior { float speed; void update ... } // Chase after another entity class ChaseBehavior extends Behavior { Entity target; void update ... } // Perform two behaviours in sequence class CombineBehavior extends Behavior { Behaviour a, b; void update ... } Essentially, Entity objects are easy to save but Behaviour objects can have a semi-complex graph of dependencies between other Entity objects and other Behaviour objects. I also have cases where a Behaviour object is shared between entities. I'm willing to change my design to make saving/loading state easier, but the above design works really well for structuring the game. Anyway, the options I've considered are: Use Java serialization. This is meant to be really slow in Android (I'll profile it sometime). I'm worried about robustness when changes are made between versions however. Use something like JSON or XML. I'm not sure how I would cope with storing the dependencies between objects however. Would I have to give each object a unique ID and then use these IDs on loading to link the right objects together? I thought I could e.g. change the ChaseBehaviour to store a ID to an entity, instead of a reference, that would be used to look up the Entity before performing the behaviour. I'd rather avoid having to write lots of loading/saving code myself as I find it really easy to make mistakes (e.g. forgetting to save something, reading things out in the wrong order). Can anyone give me any tips on good formats to save to or class designs that make saving state easier?

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• Passing objects across Appdomains

  - by MUSTAQ

  My issue is similar to the one posted in "http://stackoverflow.com/questions/981773/moving-objects-across-appdomains-in-net". In one of my application, I am creating a separate appdomain. I need to create an instance of a class (Note: this class is derived by MarshalByRefObject) in my parent domain and invoke a MethodA in that instance. This instance is created using "CreateInstanceAndUnwrap". The problem is that this MethodA takes objects of type class as an argument. These objects are not created in the MethodB where i created the appdomain. It was passed as an argument to the MethodB where i create the appdomain. So is it necessary to create a new instance of these objects using "CreateInstanceAndUnwrap" before passing it to the created domain. Not doing this gives me an error in the created domain mentioning that "MyClass object has no attribute foo" during some invocation. Please let me know how to pass the objects across appdomains and execute the method. My statements might be confusing, please let me know for any specific details required.

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• Finding the heaviest of N objects using M scales

  - by cpprulez

  We have N objects and M scales. It's up to us what the objects are, and we need to position the objects on the scales so that it is undoubtful which is the heaviest object. For example, if we have 3 objects: "a", "b", "c" and 2 scales, one possible solution is "a" "b", "b" = "c" (here "a" is the heaviest). I need an algorithm which generates such solutions given N and M. Also let's assume that "a" is always the heaviest object. I've lost a few hours figuring out how to do it, but no matter what I figure out, there's always cases which I miss. For example, another solution is: "a" + "c" = 2 * "b", "a" "c".

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• Interpreting type codes in sys.objects in SQL Server

  - by fatcat1111

  On SQL Server, the sys.objects table includes "Type" and "Type_Desc" attributes. For example: SELECT DISTINCT [Type], Type_Desc FROM Sys.Objects ORDER BY [Type] Returns: C CHECK_CONSTRAINT D DEFAULT_CONSTRAINT F FOREIGN_KEY_CONSTRAINT FN SQL_SCALAR_FUNCTION FS CLR_SCALAR_FUNCTION IT INTERNAL_TABLE P SQL_STORED_PROCEDURE PK PRIMARY_KEY_CONSTRAINT S SYSTEM_TABLE SQ SERVICE_QUEUE TR SQL_TRIGGER U USER_TABLE UQ UNIQUE_CONSTRAINT V VIEW Is there a comprehensive list of these types somewhere? There isn't a constraint on sys.objects that points me to table of these, and sys.types contains data types. I've searched SQL BOL but haven't found it. Any help would be appreciated. EDIT: Some DBs use only a subset of these types. For example, if I have a database with no views, when I query Sys.Objects as above, there are no "V" rows in the results. I am looking for a list of all possible types and descriptions used by SQL Server.

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• Defining relationship in value objects using Hibernate

  - by kate

  Hi, We have three tables .We need to get data from these tables based upon particular conditions. Like if TableA.columv=TableB.columc=tableC.column then get data. We are using value objects to map Objects to relations. Question is how to maintain these relation ships in value objects. And how to retrieve data from it. We have one value object per table.

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• Using json_encode on objects in PHP

  - by Alan

  Hi, I'm trying to output lists of objects as json and would like to know if there's a way to make objects usable to json_encode? The code I've got looks something like $related = $user->getRelatedUsers(); echo json_encode($related); Right now, I'm just iterating through the array of users and individually exporting them into arrays for json_encode to turn into usable json for me. I've already tried making the objects iterable, but json_encode just seems to skip them anyway.

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• Automatically selecting and creating class objects

  - by Omin

  Lets say that we have a box class: class Box { private int width; private int height; //Box Constructor public Box( int height ) { this.height = height; width = 450; } } and a series of Box objects in our main: Box Box1 = new Box(147); Box Box2 = new Box(178); Box Box3 = new Box(784); Is there a way to use a "for" loop to go through these objects? Also, how would you make the computer create class objects for us? eg. create 10 objects using: for( int i=0; i>10; i++) { //method }

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• Whats the best to way convert a set of Java objects to another set of objects?

  - by HDave

  Basic Java question here from a real newbie. I have a set of Java objects (of class "MyClass") that implement a certain interface (Interface "MyIfc"). I have a set of these objects stored in a private variable in my class that is declared as follows: protected Set<MyClass> stuff = new HashSet<MyClass>(); I need to provide a public method that returns this set as a collection of objects of type "MyIfc". public Collection<MyIfc> getMyStuff() {...} How do I do the conversion? The following line gives me an error that it can't do the conversion. I would have guessed the compiler knew that objects of class MyClass implemented MyIfc and therefore would have handled it. Collection<MyIfc> newstuff = stuff; Any enlightenment is appreciated.

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• Downsides to immutable objects in Java?

  - by parkr

  The advantages of immutable objects in Java seem clear: consistent state automatic thread safety simplicity You can favour immutability by using private final fields and constructor injection. But, what are the downsides to favouring immutable objects in Java? i.e. incompatibility with ORM or web presentation tools? Inflexible design? Implementation complexities? Is it possible to design a large-scale system (deep object graph) that predominately uses immutable objects?

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• c++ delete[] and array of objects

  - by osgx

  Hello I have allocated and array of Objects Objects *array = new Objects[N]; How should I delete this array? Just delete[] array; or with iterating over array's elements? for(int i=0;i<N;i++) delete array[i]; delete[]; Thanks

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• Split Java ArrayList by properties of contained Objects

  - by tzippy

  I have an ArrayList containing Objects that have a date value. Now I want to manage to create a new ArrayList for each year that contains all the Objects from the main ArrayList that have the same year in their date Value. So all Objects from 2010 go in one List, all from 1999 in another.

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• strategy to allocate/free lots of small objects

  - by aaa

  hello I am toying with certain caching algorithm, which is challenging somewhat. Basically, it needs to allocate lots of small objects (double arrays, < 256 elements), with objects accessible through mapped value, map[key] = array. time to initialized array may be quite large, generally more than 10 thousand cpu cycles. By lots I mean around gigabyte in total. objects may need to be popped/pushed as needed, generally in random places, one object at a time. lifetime of an object is generally long, minutes or more, however, object may be subject to allocation/deallocation several times during duration of program. What would be good strategy to avoid memory fragmentation, while still maintaining reasonable allocate deallocate speed? I am using C++, so I can use new and malloc. Thanks. I know there a similar questions on website, http://stackoverflow.com/questions/2156745/efficiently-allocating-many-short-lived-small-objects, are somewhat different, thread safety is not immediate issue for me.

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• System.Security.VerificationException: Operation could destabilize the runtime

  - by Rigobert Song

  I have a web service which is queried using linq to sql but returns an array of objects. I keep getting the following error: System.Security.VerificationException: Operation could destabilize the runtime When I run a method that uses a linq statement to return an array I get this error, but only on my test server, which is windows server 2008. Everything works fine in my win 7 machine. The project is a .net 3.5. Any ideas what the problem might be? Thanks UPDATE: My linq queries return IQueryable.

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• What to put as the Provider for a mocked IQueryable

  - by Vaccano

  I am working with Moles and mocking a System.Data.Linq.Table. I got it constructing fine, but when I use it, it wants IQueryable.Provider to be mocked (moled) as well. I just want it to use normal Linq To Objects. Any idea what that would be? Here is the syntax I can use: MTable<User> userTable = new System.Data.Linq.Moles.MTable<User>(); userTable.Bind(new List<User> { UserObjectHelper.TestUser() }); // this is the line that needs help MolesDelegates.Func<IQueryProvider> provider = //Insert provider here! ^ userTable.ProviderSystemLinqIQueryableget = provider | | | what can I put here? ----------------------------------------+

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• Access Edit Mode Values of BindingSource Control

  - by Christopher Edwards

  I have a BindingSource control (http://msdn.microsoft.com/en-us/library/system.windows.forms.bindingsource.aspx) with a datasource of a (single) Linq object. If I change any of the properties of the underlying Linq-to-Sql object then all the other changes on the bound controls on the form are lost. Does anyone now why and how I work around it? I don't want to call EndEdit because this will commit the changes to the underlying object. I think this might be because my underlying object linq-to-sql object does not implement IEditableObject so the potental new values for the object fields are sort of stored in the forms controls. Can anyone either clarify what is going on and/or suggest a work around. Thanks!

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• Using LinqSql, stored procedure returns datatype image problem

  - by Elias

  Hello! I´ve got a problem when using LINQ to execute a stored procedure and return its values. One of the column that the stored procedure returns is of datatype image and contains a pdf in binary form.(this because the database is deployed on sql server 2000, otherwised i would choose a blob) When including the stored procedure in my linq class its generates that my pdf columns is datatype int in the designer class. I´ve work around the problem and manually changed the datatype in representation of the stored procedure in the designer class. But when adding/removing items in the linq class the designer file re-generates and my changes are lost. Are there any better solution for my problem??

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• Building an application that includes a DB, and need recommendations

  - by Rubys

  I'm going to build a little system for personal use, and I want it to save data to a database. The language is going to be C#, and so I'd like to use this opportunity to get my head around LINQ to SQL. I have some DB experience and I know my SQL, but it was all in school using Access, which is giving me trouble, and so I'd like to use another DB, something that is small in size, easy to install, and should work with LINQ to SQL. The problem is: I don't know any except Access, and am looking for recommendations. To sum it up: I need a lightweight, easy to install, linq-to-sql supporting database for a small system on a home computer, any recommendations?

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• LinqToSql: How can I create a projection to adhere to DRY?

  - by mhutter

  Just wondering if there is a way to take some of the repitition out of a LINQ to SQL projected type. Example: Table: Address Fields: AddressID, HouseNumber, Street, City, State, Zip, +20 more Class MyAddress: AddressID, HouseNumber, Street (Only 3 fields) LINQ: from a in db.Addresses select new MyAddress { AddressID = a.AddressID, HouseNumber = a.HouseNumber, Street = a.Street } The above query works perfectly, and I understand why something like this will return all 20+ fields in each row: from a in db.Addresses select new MyAddress(a); class MyAddress { public MyAddress(Address a) { this.AddressID = a.AddressID, this.HouseNumber = a.HouseNumber, this.Street = a.Street } } Which leads me to my Question: Is it possible to implement some kind of helper function or extension method to "map" from the LINQ model to MyAddress yet only return the necessary fields in the query result rather than all of the fields?

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• How can I keep the the logic to translate a ViewModel's values to a Where clause to apply to a linq query out of My Controller?

  - by Mr. Manager

  This same problem keeps cropping up. I have a viewModel that doesn't have any persistent backing. It is just a ViewModel to generate a search input form. I want to build a large where clause from the values the user entered. If the Action Accepts as a parameter SearchViewModel How do I do this without passing my viewModel to my service layer? Service shouldn't know about ViewModels right? Oh and if I serialize it, then it would be a big string and the key/values would be strongly typed. SearchViewModel this is just a snippet. [Display(Name="Address")] public string AddressKeywords { get; set; } /// <summary> /// Gets or sets the census. /// </summary> public string Census { get; set; } /// <summary> /// Gets or sets the lot block sub. /// </summary> public string LotBlockSub { get; set; } /// <summary> /// Gets or sets the owner keywords. /// </summary> [Display(Name="Owner")] public string OwnerKeywords { get; set; } In my controller action I was thinking of something like this. but I would think all this logic doesn't belong in my Controller. ActionResult GetSearchResults(SearchViewModel model){ var query = service.GetAllParcels(); if(model.Census != null){ query = query.Where(x=>x.Census == model.Census); } if (model.OwnerKeywords != null){ query = query.Where(x=>x.Owners == model.OwnerKeywords); } return View(query.ToList()); }

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• How to get rid of this error in asp.net-mvc?

  - by Pandiya Chendur

  I am using Linq-to-sql as an ORM. I wrote this innerjoin public IQueryable<Material> FindAllMaterials() { var materials=from m in db.Materials join Mt in db.MeasurementTypes on m.MeasurementTypeId equals Mt.Id select new { m.Mat_id, m.Mat_Name, Mt.Name, m.Mat_Type }; return materials; } But when i compile this i got an error Cannot implicitly convert type 'System.Linq.IQueryable<AnonymousType#1>' to 'System.Linq.IQueryable<CrMVC.Models.Material>'. An explicit conversion exists (are you missing a cast?) Am i missing some thing... Any suggestion....

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