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  • Deserialize generic collections - coming up empty

    - by AC
    I've got a settings object for my app that has two collections in it. The collections are simple List generics that contain a collection of property bags. When I serialize it, everything is saved with no problem: XmlSerializer x = new XmlSerializer(settings.GetType()); TextWriter tw = new StreamWriter(@"c:\temp\settings.cpt"); x.Serialize(tw, settings); However when I deserialize it, everything is restored except for the two collections (verified by setting a breakpoint on the setters: XmlSerializer x = new XmlSerializer(typeof(CourseSettings)); XmlReader tr = XmlReader.Create(@"c:\temp\settings.cpt"); this.DataContext = (CourseSettings)x.Deserialize(tr); What would cause this? Everything is pretty vanilla... here's a snippet from the settings object... omitting most of it. The PresentationSourceDirectory works just fine, but the PresentationModules' setter isn't hit: private string _presentationSourceDirectory = string.Empty; public string PresentationSourceDirectory { get { return _presentationSourceDirectory; } set { if (_presentationSourceDirectory != value) { OnPropertyChanged("PresentationSourceDirectory"); _presentationSourceDirectory = value; } } } private List<Module> _presentationModules = new List<Module>(); public List<Module> PresentationModules { get { var sortedModules = from m in _presentationModules orderby m.ModuleOrder select m; return sortedModules.ToList<Module>(); } set { if (_presentationModules != value) { _presentationModules = value; OnPropertyChanged("PresentationModules"); } } }

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  • Best practice when removing entity regarding mappedBy collections?

    - by Daniel Bleisteiner
    I'm still kind of undecided which is the best practice to handle em.remove(entity) with this entity being in several collections mapped using mappedBy in JPA. Consider an entity like a Property that references three other entities: a Descriptor, a BusinessObject and a Level entity. The mapping is defined using @ManyToOne in the Property entity and using @OneToMany(mappedBy...) in the other three objects. That inverse mapping is defined because there are some situations where I need to access those collections. Whenever I remove a Property using em.remove(prop) this element is not automatically removed from managed entities of the other three types. If I don't care about that and the following page load (webapp) doesn't reload those entities the Property is still found and some decisions might be taken that are no longer true. The inverse mappings may become quite large and though I don't want to use something like descriptor.getProperties().remove(prop) because it will load all those properties that might have been lazy loaded until then. So my currently preferred way is to refresh the entity if it is managed: if (em.contains(descriptor)) em.refresh(descriptor) - which unloads a possibly loaded collection and triggers a reload upon the next access. Is there another feasible way to handle all those mappedBy collections of already loaded entites?

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  • What is "Call By Name"?

    - by forellana
    Hi to everyone! I'm working in a homework, and the professor asked me to implement the evaluation strategy called "call by name" in scheme in a certain language that we developed and he gave us an example at http://www.scala-lang.org/node/138 in the scala language, but i don't understand in what consists the call by name evaluation strategy? what differences it has with call by need? thanks, greetings

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  • Resources for learning Monads, Functors, Monoids, Arrows etc

    - by Dony Borris
    Can you people please suggest some good books / weblinks from where I can get to learn about above mentioned concepts? (Please note that I am a Java programmer and have NO prior experience with functional programming. I have been studying Scala since last one month and would appreciate the resources that try to teach the above mentioned concepts with Scala. (or even Java, if posible))

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  • How Do I Convert Pipe Delimited to Comma Delimited with Escaping

    - by Russ Bradberry
    Hi, I am fairly new to scala and I have the need to convert a string that is pipe delimited to one that is comma delimited, with the values wrapped in quotes and any quotes escaped by "\" in c# i would probably do this like this string st = "\"" + oldStr.Replace("\"", "\\\\\"").Replace("|", "\",\"") + "\"" I haven't validated that actually works but that is the basic idea behind what I am trying to do. Is there a way to do this easily in scala?

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  • Should I upgrade to Intellij Ultimate Edition?

    - by Benjamin Metz
    I am working in java and primarily Scala. I'm using the community edition of Intellij. I'm curious if its worth it to upgrade to the Ultimate Edition? I've been back and forth with Intellij and Eclipse... and for Scala dev I like Intellij a little bit better (for now). Thanks in advance...

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  • Is Odersky serious with "bills !*&^%~ code!" ?

    - by stacker
    In his book programming in scala (Chapter 5 Section 5.9 Pg 93) Odersky mentioned this expression "bills !*&^%~ code! In the footnote on same page: "By now you should be able to figure out that given this code,the Scala compiler would invoke (bills.!*&^%~(code)).!()." That's a bit to cryptic for me, could someone explain what's going on here?

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  • Functional programming approach for Java's input/output streams

    - by Elazar Leibovich
    I'm using Java's DataInputStream with scala to parse some simple binary file (which is very bad exprerience due to the lack of unsigned types, even in scala, but that's a different story). However I find myself forced to use mutable data structure, since Java's streams are inherently state preserving entities. What's a good design to wrap Java's streams with nice functional data structure?

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  • By-name repeated parameters

    - by Green Hyena
    How to pass by-name repeated parameters in Scala? The following code fails to work: scala> def foo(s: (=> String)*) = { <console>:1: error: no by-name parameter type allowed here def foo(s: (=> String)*) = { ^ Is there any other way I could pass a variable number of by name parameters to the method?

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  • Abstract attributes in Python

    - by deamon
    What is the shortest / most elegant way to implement the following Scala code with an abstract attribute in Python? abstract class Controller { val path: String } A subclass of Controller is enforced to define "path" by the Scala compiler. A subclass would look like this: class MyController extends Controller { override val path = "/home" }

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  • Common Template Library

    - by user1257547
    I'm trying to create a view that only houses reusable HTML blocks that can be used by other views. Wanted to know if something like this is possible: In views.home.common.scala.html: @component1 = { some common html } @component2 = { some other stuff } In views.home.sample.scala.html: @(user:User) import home._ @component1 @common.component2 Haven't had any luck thus far and I don't see anything similar in the samples but the idea is covered in the Template common use cases.

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  • Fibonnaci Sequence fast implementation

    - by user2947615
    I have written this function in Scala to calculate the fibonacci number given a particular index n: def fibonacci(n: Long): Long = { if(n <= 1) n else fibonacci(n - 1) + fibonacci(n - 2) } However it is not efficient when calculating with large indexes. Therefore I need to implement a function using a tuple and this function should return two consecutive values as the result. Can somebody give me any hints about this? I have never used Scala before. Thanks!

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  • should I put the jar dependancies on the shared repo or just the source files ?

    - by ashy_32bit
    We have a Scala project with few source files (in Scala and Java) and quite some dependencies in various binary formats (jar and DLL). I'm wondering what should go into our shared git repo. Only the source files (developers have to download or somehow resolve the dependencies themselves) or the both the source files and the dependencies? I may add that dependencies are all third parties and available for download for free.

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  • should I put the jar dependancies on the sahred repo or just the source files ?

    - by ashy_32bit
    We have a Scala project with few source files (in Scala and Java) and quite some dependencies in various binary formats (jar and DLL). I'm wondering what should go into our shared git repo. Only the source files (developers have to download or somehow resolve the dependencies themselves) or the both the source files and the dependencies? I may add that dependencies are all third parties and available for download for free.

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  • Why can't i define recursive variable in code block?

    - by senia
    Why can't i define a variable recursively in a code block? scala> { | val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} | } <console>:9: error: forward reference extends over definition of value fibs val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} ^ scala> val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} fibs: Stream[Int] = Stream(1, ?) lazy keyword solves this problem, but i can't understand why it works without a code block but throws a compilation error in a code block.

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  • Iterating Oracle collections of objects with out exploding them

    - by Scott Bailey
    I'm using Oracle object data types to represent a timespan or period. And I've got to do a bunch of operations that involve working with collections of periods. Iterating over collections in SQL is significantly faster than in PL/SQL. CREATE TYPE PERIOD AS OBJECT ( beginning DATE, ending DATE, ... some member functions...); CREATE TYPE PERIOD_TABLE AS TABLE OF PERIOD; -- sample usage SELECT <<period object>>.contains(period2) FROM TABLE(period_table1) t The problem is that the TABLE() function explodes the objects into scalar values, and I really need the objects instead. I could use the scalar values to recreate the objects but this would incur the overhead of re-instantiating the objects. And the period is designed to be subclassed so there would be additional difficulty trying to figure out what to initialize it as. Is there another way to do this that doesn't destroy my objects?

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  • How can I modify my classes to use it's collections in WPF TreeView

    - by Victor
    Hello, i'am trying to modify my objects to make hierarchical collection model. I need help. My objects are Good and GoodCategory: public class Good { int _ID; int _GoodCategory; string _GoodtName; public int ID { get { return _ID; } } public int GoodCategory { get { return _GoodCategory; } set { _GoodCategory = value; } } public string GoodName { get { return _GoodName; } set { _GoodName = value; } } public Good(IDataRecord record) { _ID = (int)record["ID"]; _GoodtCategory = (int)record["GoodCategory"]; } } public class GoodCategory { int _ID; string _CategoryName; public int ID { get { return _ID; } } public string CategoryName { get { return _CategoryName; } set { _CategoryName = value; } } public GoodCategory(IDataRecord record) { _ID = (int)record["ID"]; _CategoryName = (string)record["CategoryName"]; } } And I have two Collections of these objects: public class GoodsList : ObservableCollection<Good> { public GoodsList() { string goodQuery = @"SELECT `ID`, `ProductCategory`, `ProductName`, `ProductFullName` FROM `products`;"; using (MySqlConnection conn = ConnectToDatabase.OpenDatabase()) { if (conn != null) { MySqlCommand cmd = conn.CreateCommand(); cmd.CommandText = productQuery; MySqlDataReader rdr = cmd.ExecuteReader(); while (rdr.Read()) { Add(new Good(rdr)); } } } } } public class GoodCategoryList : ObservableCollection<GoodCategory> { public GoodCategoryList () { string goodQuery = @"SELECT `ID`, `CategoryName` FROM `product_categoryes`;"; using (MySqlConnection conn = ConnectToDatabase.OpenDatabase()) { if (conn != null) { MySqlCommand cmd = conn.CreateCommand(); cmd.CommandText = productQuery; MySqlDataReader rdr = cmd.ExecuteReader(); while (rdr.Read()) { Add(new GoodCategory(rdr)); } } } } } So I have two collections which takes data from the database. But I want to use thats collections in the WPF TreeView with HierarchicalDataTemplate. I saw many post's with examples of Hierarlichal Objects, but I steel don't know how to make my objects hierarchicaly. Please help.

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  • Proper usage of Java Weak Reference in case of nested collections

    - by Tong Wang
    I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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  • Java Collections.Rotate with an array doesn't work

    - by steve_72
    I have the following java code: import java.util.Arrays; import java.util.Collections; public class Test { public static void main(String[] args) { int[] test = {1,2,3,4,5}; Collections.rotate(Arrays.asList(test), -1); for(int i = 0; i < test.length; i++) { System.out.println(test[i]); } } } I want the array to be rotated, but the output I get is 1 2 3 4 5 Why is this? And is there an alternative solution?

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  • Writing a synchronized thread-safety wrapper for NavigableMap

    - by polygenelubricants
    java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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  • Problem reading from two separate InputStreams

    - by Emil H
    I'm building a Yammer client for Android in Scala and have encountered the following issue. When two AsyncTasks try to parse an XML response (not the same, each task has it's own InputStream) from the Yammer API the underlying stream throws a IOException with the message "null SSL pointer", as seen below: Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception java.lang.RuntimeException: An error occured while executing doInBackground() at android.os.AsyncTask$3.done(AsyncTask.java:200) at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:234) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:258) at java.util.concurrent.FutureTask.run(FutureTask.java:122) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673) at java.lang.Thread.run(Thread.java:1060) Caused by: java.io.IOException: null SSL pointer at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.nativeread(Native Method) at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.access$300(OpenSSLSocketImpl.java:55) at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl$SSLInputStream.read(OpenSSLSocketImpl.java:524) at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:103) at org.apache.http.impl.io.AbstractSessionInputBuffer.read(AbstractSessionInputBuffer.java:134) at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:174) at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:188) at org.apache.http.conn.EofSensorInputStream.read(EofSensorInputStream.java:178) at org.apache.harmony.xml.ExpatParser.parseFragment(ExpatParser.java:504) at org.apache.harmony.xml.ExpatParser.parseDocument(ExpatParser.java:467) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:329) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:286) at javax.xml.parsers.SAXParser.parse(SAXParser.java:361) at org.mediocre.util.XMLParser$.loadXML(XMLParser.scala:28) at org.mediocre.util.XMLParser$.loadXML(XMLParser.scala:12) ..... Searching for the error didn't give much clarity. Does this have something to do with the response from the server? Or is it something else? Complete code can be found at: http://github.com/archevel/YammerTime I get no error if I wait until the first repsponse is finished and then let the other complete. The request is made with the DefaultHttpClient, but this is supposedly thread safe. What am I missing? If anything needs to be clarified just ask :) Cheers, Emil H

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  • Niewbie OutOfMemory problem

    - by Nick
    So I am trying to create a producer/consumer type scala app. The LoopControl just sends a message to the MessageReceiver continoually. The MessageReceiver then delegates work to the MessageCreatorActor (whose work is to check a map for an object, and if not found create one and start it up). Each MessageActor created by this MessageCreatorActor is associated with an Id. Eventually this is where I want to do business logic. But I run out of memory after 15 minutes. Any help is appreciated import scala.actors.Actor import java.util.HashMap; import scala.actors.Actor._ case object LoopControl case object MessageReceiver case object MessageActor case object MessageActorCreator class MessageReceiver(msg: String) extends Actor { var messageActorMap = new HashMap[String, MessageActor] val messageCreatorActor = new MessageActorCreator(null, null) def act() { messageCreatorActor.start loop { react { case MessageActor(messageId) = if (msg.length() 0) { var messageActor = messageActorMap.get(messageId); if(messageActor == null) { messageCreatorActor ! MessageActorCreator(messageId, messageActorMap) }else { messageActor ! MessageActor } } } } } } case class MessageActorCreator(msg:String, messageActorMap: HashMap[String, MessageActor]) extends Actor { def act() { loop { react { case MessageActorCreator(messageId, messageActorMap) = if(messageId != null ) { var messageActor = new MessageActor(messageId); messageActorMap.put(messageId, messageActor) println(messageActorMap) messageActor.start messageActor ! MessageActor } } } } } class LoopControl(messageReceiver:MessageReceiver) extends Actor { var count : Int = 0; def act() { while (true) { messageReceiver ! MessageActor ("00-122-0X95-FEC0" + count) //Thread.sleep(100) count = count +1; if(count 5) { count = 0; } } } } case class MessageActor(msg: String) extends Actor { def act() { loop { react { case MessageActor = println() println("MessageActor: Got something- " + msg) } } } } object messages extends Application { val messageReceiver = new MessageReceiver("bootstrap") val loopControl = new LoopControl(messageReceiver) messageReceiver.start loopControl.start }

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