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  • When does the DENY delete rule in Core Data actually deny deletion of an object?

    - by dontWatchMyProfile
    An Employee has an inverse relationship to it's Department and vice versa. The Employee entity has an Relationship called department, and it has a DENY delete rule. Employee shall be deleted. Now: Does DENY actually deny deletion of employee, because department is still referencing a Department? Or does it mean that a Department can't be deleted because an Employee is referencing it?

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  • Chain of Responsibility Pattern: is it a good practice to have interdependent handlers?

    - by wei
    I have this scenario: I have a chain of query handlers, the first is to query the cache, if the cache can't answer it or the answer is stale, then hit a database, if it can't find the answer or the answer is stale again, then query a remote web service. But I am not sure if this is the right way to use this pattern, since the work flow is pretty much fixed, and the cache and database handlers depend on the next step's return result to refresh its records.

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  • UIEvent timestamp

    - by skajam66
    When handling a UIButton touch, you are given a UIEvent object. The UIEvent object has a timestamp which the Apple documentation states as being "the time that the event was created" (UIEvent Class Reference). In the documentation on the Main Event Loop, it states that: "The application object obtains the topmost object in the event queue, converts it to an event object (UIEvent) ..." Does [UIEvent timestamp] refer to the time at which the UIEvent object is created (i.e. after processing the touch event off of the main run loop and hance not remotely real-time) or does it refer to the time that the underlying touch object was created (and hence as close as possible to representing the actual time of the user touch9?

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  • Using Entity Framework 4.0 with Code-First and POCO: How to Get Parent Object with All its Children

    - by SirEel
    I'm new to EF 4.0, so maybe this is an easy question. I've got VS2010 RC and the latest EF CTP. I'm trying to implement the "Foreign Keys" code-first example on the EF Team's Design Blog, http://blogs.msdn.com/efdesign/archive/2009/10/12/code-only-further-enhancements.aspx. public class Customer { public int Id { get; set; public string CustomerDescription { get; set; public IList<PurchaseOrder> PurchaseOrders { get; set; } } public class PurchaseOrder { public int Id { get; set; } public int CustomerId { get; set; } public Customer Customer { get; set; } public DateTime DateReceived { get; set; } } public class MyContext : ObjectContext { public RepositoryContext(EntityConnection connection) : base(connection){} public IObjectSet<Customer> Customers { get {return base.CreateObjectSet<Customer>();} } } I use a ContextBuilder to configure MyContext: { var builder = new ContextBuilder<MyContext>(); var customerConfig = _builder.Entity<Customer>(); customerConfig.Property(c => c.Id).IsIdentity(); var poConfig = _builder.Entity<PurchaseOrder>(); poConfig.Property(po => po.Id).IsIdentity(); poConfig.Relationship(po => po.Customer) .FromProperty(c => c.PurchaseOrders) .HasConstraint((po, c) => po.CustomerId == c.Id); ... } This works correctly when I'm adding new Customers, but not when I try to retrieve existing Customers. This code successfully saves a new Customer and all its child PurchaseOrders: using (var context = builder.Create(connection)) { context.Customers.AddObject(customer); context.SaveChanges(); } But this code only retrieves Customer objects; their PurchaseOrders lists are always empty. using (var context = _builder.Create(_conn)) { var customers = context.Customers.ToList(); } What else do I need to do to the ContextBuilder to make MyContext always retrieve all the PurchaseOrders with each Customer?

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  • How should I implement simple caches with concurrency on Redis?

    - by solublefish
    Background I have a 2-tier web service - just my app server and an RDBMS. I want to move to a pool of identical app servers behind a load balancer. I currently cache a bunch of objects in-process. I hope to move them to a shared Redis. I have a dozen or so caches of simple, small-sized business objects. For example, I have a set of Foos. Each Foo has a unique FooId and an OwnerId. One "owner" may own multiple Foos. In a traditional RDBMS this is just a table with an index on the PK FooId and one on OwnerId. I'm caching this in one process simply: Dictionary<int,Foo> _cacheFooById; Dictionary<int,HashSet<int>> _indexFooIdsByOwnerId; Reads come straight from here, and writes go here and to the RDBMS. I usually have this invariant: "For a given group [say by OwnerId], the whole group is in cache or none of it is." So when I cache miss on a Foo, I pull that Foo and all the owner's other Foos from the RDBMS. Updates make sure to keep the index up to date and respect the invariant. When an owner calls GetMyFoos I never have to worry that some are cached and some aren't. What I did already The first/simplest answer seems to be to use plain ol' SET and GET with a composite key and json value: SET( "ServiceCache:Foo:" + theFoo.Id, JsonSerialize(theFoo)); I later decided I liked: HSET( "ServiceCache:Foo", theFoo.FooId, JsonSerialize(theFoo)); That lets me get all the values in one cache as HVALS. It also felt right - I'm literally moving hashtables to Redis, so perhaps my top-level items should be hashes. This works to first order. If my high-level code is like: UpdateCache(myFoo); AddToIndex(myFoo); That translates into: HSET ("ServiceCache:Foo", theFoo.FooId, JsonSerialize(theFoo)); var myFoos = JsonDeserialize( HGET ("ServiceCache:FooIndex", theFoo.OwnerId) ); myFoos.Add(theFoo.OwnerId); HSET ("ServiceCache:FooIndex", theFoo.OwnerId, JsonSerialize(myFoos)); However, this is broken in two ways. Two concurrent operations can read/modify/write at the same time. The latter "wins" the final HSET and the former's index update is lost. Another operation could read the index in between the first and second lines. It would miss a Foo that it should find. So how do I index properly? I think I could use a Redis set instead of a json-encoded value for the index. That would solve part of the problem since the "add-to-index-if-not-already-present" would be atomic. I also read about using MULTI as a "transaction" but it doesn't seem like it does what I want. Am I right that I can't really MULTI; HGET; {update}; HSET; EXEC since it doesn't even do the HGET before I issue the EXEC? I also read about using WATCH and MULTI for optimistic concurrency, then retrying on failure. But WATCH only works on top-level keys. So it's back to SET/GET instead of HSET/HGET. And now I need a new index-like-thing to support getting all the values in a given cache. If I understand it right, I can combine all these things to do the job. Something like: while(!succeeded) { WATCH( "ServiceCache:Foo:" + theFoo.FooId ); WATCH( "ServiceCache:FooIndexByOwner:" + theFoo.OwnerId ); WATCH( "ServiceCache:FooIndexAll" ); MULTI(); SET ("ServiceCache:Foo:" + theFoo.FooId, JsonSerialize(theFoo)); SADD ("ServiceCache:FooIndexByOwner:" + theFoo.OwnerId, theFoo.FooId); SADD ("ServiceCache:FooIndexAll", theFoo.FooId); EXEC(); //TODO somehow set succeeded properly } Finally I'd have to translate this pseudocode into real code depending how my client library uses WATCH/MULTI/EXEC; it looks like they need some sort of context to hook them together. All in all this seems like a lot of complexity for what has to be a very common case; I can't help but think there's a better, smarter, Redis-ish way to do things that I'm just not seeing. How do I lock properly? Even if I had no indexes, there's still a (probably rare) race condition. A: HGET - cache miss B: HGET - cache miss A: SELECT B: SELECT A: HSET C: HGET - cache hit C: UPDATE C: HSET B: HSET ** this is stale data that's clobbering C's update. Note that C could just be a really-fast A. Again I think WATCH, MULTI, retry would work, but... ick. I know in some places people use special Redis keys as locks for other objects. Is that a reasonable approach here? Should those be top-level keys like ServiceCache:FooLocks:{Id} or ServiceCache:Locks:Foo:{Id}? Or make a separate hash for them - ServiceCache:Locks with subkeys Foo:{Id}, or ServiceCache:Locks:Foo with subkeys {Id} ? How would I work around abandoned locks, say if a transaction (or a whole server) crashes while "holding" the lock?

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  • Unable to cast object of type 'System.Byte[]' to type 'System.IConvertible'.

    - by alvn.dsza
    i get the error in following code Function ReadFile(ByVal sPath As String) As Byte Dim data As Byte data = Nothing Dim fInfo As FileInfo fInfo = New FileInfo(sPath) Dim numBytes As Long numBytes = fInfo.Length Dim fStream As FileStream fStream = New FileStream(sPath, FileMode.Open, FileAccess.Read) Dim br As BinaryReader br = New BinaryReader(fStream) data = Convert.ToByte(br.ReadBytes(numBytes)) `getting error on this line` Return data End Function

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  • How to convert SQL Statement with TOP, COUNT and GROUP BY to return an object list with LINQ

    - by Junior Mayhé
    Hello guys does anyone know how to convert this SQL statement to a LINQ to a List? SELECT TOP(5) COUNT(CategoryId), CategoryName FROM Tickets GROUP BY CategoryName The result would be something like public static List<Categories> List() { MyEntities db = new MyEntities(); /* here it should return a list o Category type */; return db.Category.GroupBy(...).OrderBy(...); }

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  • How do I create another controller action to create an object in rails?

    - by Angela
    I have a model called Contact_Email. When an Email template is sent through ActionMailer to a specific Contact, as part of the Create action it sends it through upon .save. However, I want to create a "skip" action which also creates a Contact_Email, but does NOT send an ActionMailer and allows me to set the status differently. I want to create a separate action because I want to make this respond to a remote_for_tag so that I can just have an ajax button indicate it has been "skipped": Here's what I tried, but while it creates a Contact_Email, I end up getting an error when I want to go back and view all the Contacts again. def skip @contact_email = ContactEmail.new @contact_email.contact_id = params[:contact_id] @contact_email.email_id = params[:email_id] @contact_email.status = "skipped" if @contact_email.save flash[:notice] = "skipped email" redirect_to contact_emails_url end end

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  • test php disabled caching

    - by user1691389
    My site had a problem in that certain browsers (especially opera and gecko) were "over-caching" (caching far too much for my taste). I've just added the following PHP snippet to hopefully disable caching in all browsers: <?php header("Expires: Tue, 01 Jan 2000 00:00:00 GMT"); header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); header("Cache-Control: no-store, no-cache, must-revalidate, max-age=0"); header("Cache-Control: post-check=0, pre-check=0", false); header("Pragma: no-cache"); ?> Question: How would you test this out, to make sure it actually works?

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  • How to get maximum/largest value from json object with Android?

    - by blankon91
    I've json string like this: {"GetReportResult":[ {"bulan":"4","total":"2448","type":"CHEESE1K","uang":"8847823"},{"bulan":"4","total":"572476","type":"ESL","uang":"5863408410"},{"bulan":"4","total":"46008","type":"ESL500ML","uang":"234498301"},{"bulan":"4","total":"228985","type":"UHT","uang":"1367172990"},{"bulan":"4","total":"40995","type":"WHP","uang":"235750452"},{"bulan":"5","total":"5703","type":"CHEESE1K","uang":"134929306"},{"bulan":"5","total":"648663","type":"ESL","uang":"6645764498"},{"bulan":"5","total":"49305","type":"ESL500ML","uang":"266817346"},{"bulan":"5","total":"287867","type":"UHT","uang":"1446897805"},{"bulan":"5","total":"51958","type":"WHP","uang":"631994613"},{"bulan":"6","total":"4390","type":"CHEESE1K","uang":"104527773"},{"bulan":"6","total":"443335","type":"ESL","uang":"4540123082"},{"bulan":"6","total":"28462","type":"ESL500ML","uang":"148290912"},{"bulan":"6","total":"213250","type":"UHT","uang":"1197646870"},{"bulan":"6","total":"27049","type":"WHP","uang":"189802525"} ]} I want to get maximum/largest value of bulan, which is 6. How to do that on android?

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  • Is an object still connected to a list after FirstOrDefault?

    - by Cynthia
    Here's my code: Event thisEvent = (from i in list where (i.eventID == eventID) select i).FirstOrDefault(); if (thisEvent != null) { thisEvent.eventResolved = resolved; thisEvent.eventSequence.Add(item); } "list" is a collection of IEnumerable, i.e. IEnumerable<Event> list; What I'm wondering is: after creating thisEvent using FirstOrDefault, is thisEvent still connected to list? In other words, when I change the two properties, eventResolved and eventSequence, is "list" actually changed, or is thisEvent just some totally disconnected copy of an item in "list"?

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  • How do I ensure jQuery ajax call does not send a local copy of file?

    - by Tommy
    $.ajax({ type: 'GET', url: "string.txt", cache: false, success: function(str){ alert("Data is: "+ str); } }); In this example, string.txt is still sent to the cache (\Temporary Internet Files) How do I ensure that the file is not sent - read from the server only? Am I missing an option? I set cache to false but that does not block it from being sent to client. For example, ajax POST does not send a local copy..... Thanks

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  • When exactly is constructor of static local object called?

    - by Honza Bambas
    Say we have a code like this: Some class { Some() { // the ctor code } }; Some& globalFunction() { static Some gSome; return gSome; } When exactly 'the ctor code' is executed? As for normal static variables before main() or at the moment we first call to 'globalFunction()'? How is it on different platforms and different compilers (cl, gcc, ...) ? Thanks -hb-

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  • How to get the field name of a java (weak) reference pointing to an object in an other class?

    - by Tom
    Imagine I have the following situation: Test1.java import java.lang.ref.WeakReference; public class Test1 { public WeakReference fieldName; public init() { fieldName = new WeakReference(this); Test2.setWeakRef(fieldName); } } Test2.java import java.lang.ref.WeakReference; public class Test2 { public static setWeakRef(WeakReference weakRef) { //at this point I got weakRef in an other class.. now, how do I get the field name this reference was created with? So that it returns exactly "fieldName", because that's the name I gave it in Test1.java? } } At the location of the comment I received the weak reference created in an other class. How would I retreive the field name that this weak reference was created with, in this case "fieldName"? Thanks in advance.

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  • How do I add a where filter using the original Linq-to-SQL object in the following scenario

    - by GenericTypeTea
    I am performing a select query using the following Linq expression: Table<Tbl_Movement> movements = context.Tbl_Movement; var query = from m in movements select new MovementSummary { Id = m.DocketId, Created = m.DateTimeStamp, CreatedBy = m.Tbl_User.FullName, DocketNumber = m.DocketNumber, DocketTypeDescription = m.Ref_DocketType.DocketType, DocketTypeId = m.DocketTypeId, Site = new Site() { Id = m.Tbl_Site.SiteId, FirstLine = m.Tbl_Site.FirstLine, Postcode = m.Tbl_Site.Postcode, SiteName = m.Tbl_Site.SiteName, TownCity = m.Tbl_Site.TownCity, Brewery = new Brewery() { Id = m.Tbl_Site.Ref_Brewery.BreweryId, BreweryName = m.Tbl_Site.Ref_Brewery.BreweryName }, Region = new Region() { Description = m.Tbl_Site.Ref_Region.Description, Id = m.Tbl_Site.Ref_Region.RegionId } } }; I am also passing in an IFilter class into the method where this select is performed. public interface IJobFilter { int? PersonId { get; set; } int? RegionId { get; set; } int? SiteId { get; set; } int? AssetId { get; set; } } How do I add these where parameters into my SQL expression? Preferably I'd like this done in another method as the filtering will be re-used across multiple repositories. Unfortunately when I do query.Where it has become an IQueryable<MovementSummary>. I'm assuming it has become this as I'm returning an IEnumerable<MovementSummary>. I've only just started learning LINQ, so be gentle.

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  • How to enforce a 5-minute per post rule in a session object in Java?

    - by John
    I'm trying to figure out how to enforce a 5 minute per post/action rule. I'm developing a web application with Wicket in Java and I've got a session class which I was planning on using to keep track of these timers on a per-user basis. I wasn't planning on storing the timestamp in a database. public boolean isAllowedToPost() { if(null OR has 5 minutes passed since last post) { // set the new timestamp return true; } else { return false; } }

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  • Programmatically determine whether to describe an object with "a" or "an"?

    - by MarathonStudios
    I have a database of nouns (ex "house", "exclamation point", "apple") that I need to output and describe in my application. It's hard to put together a natural-sounding sentence to describe an item without using "a" or "an" - "a house is BIG", "an exclamation point is SMALL", etc. Is there any function, library, or hack i can use in PHP to determine whether it is more appropriate to describe any given noun with A or AN?

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  • What was the thinking behind the development of Object Oriented Programming?

    - by leeand00
    I've got some real nay-sayers on my hands here, and I'm trying to give them the reason why OOP was developed in the first place. I realize that OOP is not perfect for all problems and situations, but it was developed for a reason... My guess would be, that a few of those reasons would be: Maintainability Re-usability Document-ability Abstraction of Complex Technologies Dynamic Extension at Runtime... Probably some things that I'm not even aware of yet... But I really don't have much to back this up, and I was wondering why OOP was developed in the first place, and it's history. What were the people who developed OOP trying to accomplish? What led them to develop OOP?

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