predicate

I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic to in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm getting the exception [System.NotSupportedException] --- {"The LINQ expression node type 'Invoke' is not

I have a vector (order is important) of objects (lets call them myobj class) where I'm trying to delete multiple objects at a time. class vectorList { vector<*myobj> myList; }; class myobj { char* myName; int index; bool m_bMarkedDelete; } I was thinking that the best way to do this would be to mark specific myobj objects for deletion and then call myList.remove_if() on the vector. However, I'm not exactly sure how to use predicates and such for this. Should I create a member variable in the object which allows me to say that I want to delete the myobj and then create a predicate which checks

Google Guava has a predicate that always returns true . Does Java 8 have something similar for its Predicate ? I know I could use (foo)->{return true;} , but I want something pre-made, analogous to Collections.emptySet() . There are no built-in always-true and always-false predicates in Java 8. The most concise way to write these is x -> true and x -> false Compare these to Predicates.alwaysTrue() // Guava and finally to an anonymous inner class: new Predicate<Object>() { public boolean test(Object x) { return true; } } Probably the reason that Guava has these built-in predicates is that there

I have an attribute of type BOOL and I want to perform a search for all managed objects where this attribute is YES . For string attributes it is straightforward. I create a predicate like this: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"userName = %@", userName]; But how do I do this, if I have a bool attribute called selected and I want to make a predicate for this? Could I just do something like this? NSPredicate *predicate = [NSPredicate predicateWithFormat:@"selected = %@", yesNumber]; Or do I need other format specifiers and just pass YES ? From Predicate Programming

It seems that this question was not discussed on stackoverflow before, save for Working With Nested XPath Predicates ... Refined where the solution not involving nested predicates was offered. So I tried to write the oversimplified sample of what I'd like to get: Input: <root> <shortOfSupply> <food animal="doggie"/> <food animal="horse"/> </shortOfSupply> <animalsDictionary> <cage name="A" animal="kittie"/> <cage name="B" animal="dog"/> <cage name="C" animal="cow"/> <cage name="D" animal="zebra"/> </animals> </root> Output: <root> <hungryAnimals> <cage name="B"/> <cage name="D"/> <

How can I apply multiple predicates to a java.util.Stream's filter() method? This is what I do now, but I don't really like it. I have a Collection of things and I need to reduce the number of things based on the Collection of filters (predicates): Collection<Thing> things = someGenerator.someMethod(); List<Thing> filtered = things.parallelStream().filter(p -> { for (Filter f : filtersCollection) { if (f.test(p)) return true; } return false; }).collect(Collectors.toList()); I know that if I knew number of filters up-front, I could do something like this: List<Thing> filtered = things

Im trying to fetch all the objects in an entity matching a user selectedDate (it's an NSDate). The Core Data code is fine but my predicate keeps returning 0 results, the dates are the same in the database as the user is selecting. How should the selectedDate be compared with a date from an entity using a predicate? NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(eDate = %@)", selectedDate]; Your predicate looks to be fine. The reason you're finding zero result are returned however may be that the dates aren't entirely the same. For example: 05/04/2012 13:37:00 will not match with

Is there any way in c# .NET 2.0! to combine multiple Predicates? Let's say I have the following code. List<string> names = new List<string>(); names.Add("Jacob"); names.Add("Emma"); names.Add("Michael"); names.Add("Isabella"); names.Add("Ethan"); names.Add("Emily"); List<string> filteredNames = names.FindAll(StartsWithE); static bool StartsWithE(string s) { if (s.StartsWith("E")) { return true; } else { return false; } } This gives me: Emma Ethan Emily So this is pretty cool stuff, but I know want to be able to filter using multiple predicates. So I want to be able to say something like this: