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  • Rating System Database Structure

    - by Harsha M V
    I have two entity groups. Restaurants and Users. Restaurants can be rated (1-5) by users. And rating fromeach user should be retrievable. Resturant(id, name, ..... , total_number_of_votes, total_voting_points ) User (id, name ...... ) Rating (id, restaurant_id, user_id, rating_value) Do i need to store the avg value so that it need not be calculated every time ? which table is the best place to store avg_rating, total_no_of_votes, total_voting_points ?

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  • Core Data: Deleting causes 'NSObjectInaccessibleException' from NSOperation with a reference to a deleted object

    - by Bryan Irace
    My application has NSOperation subclasses that fetch and operate on managed objects. My application also periodically purges rows from the database, which can result in the following race condition: An background operation fetches a bunch of objects (from a thread-specific context). It will iterate over these objects and do something with their properties. A bunch of rows are deleted in the main managed object context. The background operation accesses a property on an object that was deleted from the main context. This results in an 'NSObjectInaccessibleException', reason: 'CoreData could not fulfill a fault' Ideally, the objects that are fetched by the NSOperation can be operated on even if one is deleted in the main context. The best way I can think to achieve this is either to: Call [request setReturnsObjectsAsFaults:NO] to ensure that Core Data won't try to fulfill a fault for an object that no longer exists in the main context. The problem here is I may need to access the object's relationships, which (to my understanding) will still be faulted. Iterate through the managed objects up front and copy the properties I will need into separate non-managed objects. The problem here is that (I think) I will need to synchronize/lock this part, in case an object is deleted in the main context before I can finish copying. Am I missing something obvious? It doesn't seem like what I'm trying to accomplish is too out of the ordinary. Thanks for your help.

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  • Cast LINQ Function Result to Domain Object

    - by Alex
    Hello, I have a table valued function to perform full text search on SQL server. The result type of my full text search function in LINQ is a special autogenerated type which includes KEY and RANK in addition to my regular domain object properties. So, if my regular domain object is PERSONS (with properties FirstName, LastName etc.), I also have a result object PERSONS_FTSResult with the same properties + KEY and RANK. Is there an easy way to cast it back to PERSONS?

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  • Dynamic object property populator (without reflection)

    - by grenade
    I want to populate an object's properties without using reflection in a manner similar to the DynamicBuilder on CodeProject. The CodeProject example is tailored for populating entities using a DataReader or DataRecord. I use this in several DALs to good effect. Now I want to modify it to use a dictionary or other data agnostic object so that I can use it in non DAL code --places I currently use reflection. I know almost nothing about OpCodes and IL. I just know that it works well and is faster than reflection. I have tried to modify the CodeProject example and because of my ignorance with IL, I have gotten stuck on two lines. One of them deals with dbnulls and I'm pretty sure I can just lose it, but I don't know if the lines preceding and following it are related and which of them will also need to go. The other, I think, is the one that pulled the value out of the datarecord before and now needs to pull it out of the dictionary. I think I can replace the "getValueMethod" with my "property.Value" but I'm not sure. I'm open to alternative/better ways of skinning this cat too. Here's the code so far (the commented out lines are the ones I'm stuck on): using System; using System.Collections.Generic; using System.Reflection; using System.Reflection.Emit; public class Populator<T> { private delegate T Load(Dictionary<string, object> properties); private Load _handler; private Populator() { } public T Build(Dictionary<string, object> properties) { return _handler(properties); } public static Populator<T> CreateBuilder(Dictionary<string, object> properties) { //private static readonly MethodInfo getValueMethod = typeof(IDataRecord).GetMethod("get_Item", new [] { typeof(int) }); //private static readonly MethodInfo isDBNullMethod = typeof(IDataRecord).GetMethod("IsDBNull", new [] { typeof(int) }); Populator<T> dynamicBuilder = new Populator<T>(); DynamicMethod method = new DynamicMethod("Create", typeof(T), new[] { typeof(Dictionary<string, object>) }, typeof(T), true); ILGenerator generator = method.GetILGenerator(); LocalBuilder result = generator.DeclareLocal(typeof(T)); generator.Emit(OpCodes.Newobj, typeof(T).GetConstructor(Type.EmptyTypes)); generator.Emit(OpCodes.Stloc, result); int i = 0; foreach (var property in properties) { PropertyInfo propertyInfo = typeof(T).GetProperty(property.Key, BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase | BindingFlags.FlattenHierarchy | BindingFlags.Default); Label endIfLabel = generator.DefineLabel(); if (propertyInfo != null && propertyInfo.GetSetMethod() != null) { generator.Emit(OpCodes.Ldarg_0); generator.Emit(OpCodes.Ldc_I4, i); //generator.Emit(OpCodes.Callvirt, isDBNullMethod); generator.Emit(OpCodes.Brtrue, endIfLabel); generator.Emit(OpCodes.Ldloc, result); generator.Emit(OpCodes.Ldarg_0); generator.Emit(OpCodes.Ldc_I4, i); //generator.Emit(OpCodes.Callvirt, getValueMethod); generator.Emit(OpCodes.Unbox_Any, property.Value.GetType()); generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod()); generator.MarkLabel(endIfLabel); } i++; } generator.Emit(OpCodes.Ldloc, result); generator.Emit(OpCodes.Ret); dynamicBuilder._handler = (Load)method.CreateDelegate(typeof(Load)); return dynamicBuilder; } } EDIT: Using Marc Gravell's PropertyDescriptor implementation (with HyperDescriptor) the code is simplified a hundred-fold. I now have the following test: using System; using System.Collections.Generic; using System.ComponentModel; using Hyper.ComponentModel; namespace Test { class Person { public int Id { get; set; } public string Name { get; set; } } class Program { static void Main() { HyperTypeDescriptionProvider.Add(typeof(Person)); var properties = new Dictionary<string, object> { { "Id", 10 }, { "Name", "Fred Flintstone" } }; Person person = new Person(); DynamicUpdate(person, properties); Console.WriteLine("Id: {0}; Name: {1}", person.Id, person.Name); Console.ReadKey(); } public static void DynamicUpdate<T>(T entity, Dictionary<string, object> properties) { foreach (PropertyDescriptor propertyDescriptor in TypeDescriptor.GetProperties(typeof(T))) if (properties.ContainsKey(propertyDescriptor.Name)) propertyDescriptor.SetValue(entity, properties[propertyDescriptor.Name]); } } } Any comments on performance considerations for both TypeDescriptor.GetProperties() & PropertyDescriptor.SetValue() are welcome...

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  • iPhone: Core Data save Class object

    - by Nic Hubbard
    I have an entity in core data called Location. Inside this I have a few fields, such as date. But, I would also like to save a class object in it that I created called Annotation. What type of attribute would I use for this, since it is a custom class object that I created? Location (object) |__ Date |__ Annotation (MKAnnotation protocol)

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  • phpUnit - mock php extended exception object

    - by awongh
    I'm testing some legacy code that extends the default php exception object. This code prints out a custom HTML error message. I would like to mock this exception object in such a way that when the tested code generates an exception it will just echo the basic message instead of giving me the whole HTML message. I cannot figure out a way to do this. It seems like you can test for explicit exceptions, but you can't change in a general way the behavior of an exception, and you also can't mock up an object that extends a default php functionality. ( can't think of another example of this beyond exceptions... but it would seem to be the case ) I guess the problem is, where would you attach the mocked object?? It seems like you can't interfere with 'throw new' and this is the place that the object method is called.... Or if you could somehow use the existing phpunit exception functionality to change the exception behavior the way you want, in a general way for all your code... but this seems like it would be hacky and bad....

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  • Passing user context to from impersonated thread to outproc COM object

    - by Thumbeti
    Hi, I am writing a CPP program on windows 2k3 where i want to achieve the following thing. Pass the user context from the impersonated thread to a outproc COM component. Steps what i m trying in details are: 1) Start an execution of exe with user USR1 2) Impersonate the current thread with USR2 3) Initiate a API on outproc COM object. And this COM object should run with USR2 What is happening: on 3rd step, COM object is getting started with USR1 only. Can anybody help me in passing the user context to COM object. Thanks in advance, Thumbeti

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  • Database that consumes less disk space

    - by Hugo Palma
    I'm looking at solutions to store a massive quantity of information consuming the less possible disk space. The information structure is very simple and the queries will also be very simple. I've looked at solutions like Apache Cassandra and relations databases but couldn't find a comparison where disk usage is mentioned. Any ideas on this would be great.

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  • Put an object in Handler message

    - by Tsimmi
    Hi! I need to download an image from the internet, in a different thread, and then send that image object in the handler message, to the UI thread. I already have this: ... Message msg = Message.obtain(); Bundle b = new Bundle(); b.putParcelable("MyObject", (Parcelable) object); msg.setData(b); handler.sendMessage(msg); And when I receive this message, I want to extract the object: ... public void handleMessage(Message msg) { super.handleMessage(msg); MyObject objectRcvd = (MyObject) msg.getData().getParcelable("IpTile"); addToCache(ipTile); mapView.invalidate(); } But this is giving me: ...java.lang.ClassCastException... Can anyone help? And by the way, is this the most efficient way to pass an object to the UI Thread? Thank you all!

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  • Killing COM object from C#

    - by Pradeep
    I have a COM object that we are calling from C#. This works great, and I have my own pool of objects that I can use whenever I want. Now I need to kill the object. I've tried releasing the COM object explicitly and then garbage collecting from another thread, but that does nothing. Does anyone have any other ideas to kill this object? Thanks for the help. I've tried System.Runtime.InteropServices.Marshal.ReleaseComObject(myApp); GC.Collect(); GC.WaitForPendingFinalizers (); myApp = null; and I create it by myApplication.ApplicationClass myApp = new myApplication.ApplicationClass(); Thanks, Pradeep

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  • determining name of object loaded in R

    - by andrewj
    Imagine you have an object foo that you saved as saved.file.rda as follows: foo <- 'a' save(foo, file='saved.file.rda') Suppose you load saved.file.rda into an environment with multiple objects but forgot the name of the object that is in saved.file.rda. Is there a way in R to determine that name? You can do it the following way, which seems a little clunky: bar <- load('saved.file.rda') eval(parse(text=bar)) # this will pull up the object that was in saved.file.rda However, is there a better way of doing this?

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  • Inexpensive ways to add seek to a filetype object

    - by becomingGuru
    PdfFileReader reads the content from a pdf file to create an object. I am querying the pdf from a cdn via urllib.urlopen(), this provides me a file like object, which has no seek. PdfFileReader, however uses seek. What is the simple way to create a PdfFileReader object from a pdf downloaded via url. Now, what can I do to avoid writing to disk and reading it again via file(). Thanks in advance.

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  • index 'enabled' fields good idea?

    - by sibidiba
    Content of a website is stored in a MySQL database. 99% of the content will be enabled, but some (users, posts etc.) will be disabled. Most of the queries end as WHERE (...) AND enabled Is it a good idea to create an index on the field 'enabled'?

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  • Object serialization practical uses?

    - by nash
    How many software projects have you worked on used object serialization? I personally never came across a scenario where object serialization was used. One use case i can think of is, a server software storing objects to disk to save memory. Are there other types of software where object serialization is essential or preferred over a database?

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  • PHP: How to access array values returned by a static function?

    - by Prashant
    I am running following code, getAccount() is a static function, $ac_info = AccountClass::getAccount($ac_code); print_r($ac_info); and getting following output AccountClass Object ( [account_code] => [email protected] [username] => XYZ [email] => [first_name] => [last_name] => [company_name] => [id] => [email protected] [balance_in_cents] => 0 [created_at] => 1271333048 [state] => active ) But I want to access the value of "account_code" shown above, how to access it, and AccountClass Object what is this, this is array or what? I am not getting it properly. Please explain what is AccountClass Object and how to access value of properties account_code, first_name inside this array. Thanks

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  • Javascript new object (function ) vs inline invocation

    - by Sheldon Ross
    Is there any considerations to determine which is better practice for creating an object with private members? var object = new function () { var private = "private variable"; return { method : function () { ..dosomething with private; } } } VS var object = function () { ... }(); Basically what is the difference between using NEW here, and just invoking the function immediately after we define it?

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  • window.setInterval from inside an object

    - by Keith Rousseau
    I'm currently having an issue where I have a javascript object that is trying to use setInterval to call a private function inside of itself. However, it can't find the object when I try to call it. I have a feeling that it's because window.setInterval is trying to call into the object from outside but doesn't have a reference to the object. FWIW - I can't get it to work with the function being public either. The basic requirement is that I may need to have multiple instances of this object to track multiple uploads that are occurring at once. If you have a better design than the current one or can get the current one working then I'm all ears. The following code is meant to continuously ping a web service to get the status of my file upload: var FileUploader = function(uploadKey) { var intervalId; var UpdateProgress = function() { $.get('someWebService', {}, function(json) { alert('success'); }); }; return { BeginTrackProgress: function() { intervalId = window.setInterval('UpdateProgress()', 1500); }, EndTrackProgress: function() { clearInterval(intervalId); } }; }; This is how it is being called: var fileUploader = new FileUploader('myFileKey'); fileUploader.BeginTrackProgress();

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  • How to code a C# Extension method to turn a Domain Model object into an Interface object?

    - by Dr. Zim
    When you have a domain object that needs to display as an interface control, like a drop down list, ifwdev suggested creating an extension method to add a .ToSelectList(). The originating object is a List of objects that have properties identical to the .Text and .Value properties of the drop down list. Basically, it's a List of SelectList objects, just not of the same class name. I imagine you could use reflection to turn the domain object into an interface object. Anyone have any suggestions for C# code that could do this? The SelectList is an MVC drop down list of SelectListItem. The idea of course is to do something like this in the view: <%= Html.DropDownList("City", (IEnumerable<SelectListItem>) ViewData["Cities"].ToSelectList() )

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  • A table that has relation to itself issue

    - by Mostafa
    Hi , I've defined table with this schema : CREATE TABLE [dbo].[Codings]( [Id] [int] IDENTITY(1,1) NOT NULL, [ParentId] [int] NULL, [CodeId] [int] NOT NULL, [Title] [nvarchar](50) COLLATE Arabic_CI_AI NOT NULL, CONSTRAINT [PK_Codings] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] And fill it up with data like this : Id ParentId CodeId Title ----------- ----------- ----------- ---------- 1 NULL 0 Gender 2 1 1 Male 3 1 2 Female 4 NULL 0 Educational Level 5 4 1 BS 6 4 2 MS 7 4 3 PHD Now , I'm looking for a solution , in order , When i delete a record that is parent ( like Id= 1 or 4 ), It delete all child automatically ( all records that their ParentId is 1 or 4 ) . I supposed i can do it via relation between Id and Parent Id ( and set cascade for delete rule ) , But when i do that in MMS , the Delete Rule or Update Rule in Properties is disabled . My question is , What can i do to accomplish this ? Thank you

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  • Database Modelling - Conceptually different entities but with near identical fields

    - by Andrew Shepherd
    Suppose you have two sets of conceptual entities: MarketPriceDataSet which has multiple ForwardPriceEntries PoolPriceForecastDataSet which has multiple PoolPriceForecastEntry Both different child objects have near identical fields: ForwardPriceEntry has MarketPriceDataSetId (foreign key to parent table) StartDate EndDate SimulationItemId ForwardPrice PoolPriceForecastEntry has PoolPriceForecastDataSetId (foreign key to parent table) StartDate EndDate SimulationItemId ForecastPoolPrice If I modelled them as separate tables, the only difference would be the foreign key, and the name of the price field. There has been a debate as to whether the two near identical tables should be merged into one. Options I've thought of to model this is: Just keep them as two independent, separate tables Have both sets in the one table with an additional "type" field, and a parent_id equalling a foreign key to either parent table. This would sacrifice referential integrity checks. Have both sets in the one table with an additional "type" field, and create a complicated sequence of joining tables to maintain referential integrity. What do you think I should do, and why?

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  • Joining Tables Based on Foreign Keys

    - by maestrojed
    I have a table that has a lot of fields that are foreign keys referencing a related table. I am writing a script in PHP that will do the db queries. When I query this table for its data I need to know the values associated with these keys not the key. How do most people go about this? A 101 way to do this would be to query this table for its data including the foreign keys and then query the related tables to get each key's value. This could be a lot of queries (~10). Question 1: I think I could write 1 query with a bunch of joins. Would that be better? This approach also requires the querying script to know which table fields are foreign keys. Since I have many tables like this but all with different fields, this means writing nice generic functions is hard. MySQL InnoDB tables allow for foreign constraints. I know the database has these set up correctly. Question 2: What about the idea of querying the table and identifying what the constraints are and then matching them up using whatever process I decide on from Question 1. I like this idea but never see it being used in code. Makes me think its not a good idea for some reason. I would use something like SHOW CREATE TABLE tbl_name; to find what constraints/relationships exist for that table. Thank you for any suggestions or advice.

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