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  • Avoiding NPE in trait initialization without using lazy vals

    - by 0__
    This is probably covered by the blog entry by Jesse Eichar—still I can't figure out how to correct the following without residing to lazy vals so that the NPE is fixed: Given trait FooLike { def foo: String } case class Foo( foo: String ) extends FooLike trait Sys { type D <: FooLike def bar: D } trait Confluent extends Sys { type D = Foo } trait Mixin extends Sys { val global = bar.foo } First attempt: class System1 extends Mixin with Confluent { val bar = Foo( "npe" ) } new System1 // boom!! Second attempt, changing mixin order class System2 extends Confluent with Mixin { val bar = Foo( "npe" ) } new System2 // boom!! Now I use both bar and global very heavily, and therefore I don't want to pay a lazy-val tax just because Scala (2.9.2) doesn't get the initialisation right. What to do?

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  • Functional languages targeting the LLVM

    - by Matthew
    Are there any languages that target the LLVM that: Are statically typed Use type inference Are functional (i.e. lambda expressions, closures, list primitives, list comprehensions, etc.) Have first class object-oriented features (inheritance, polymorphism, mixins, etc.) Have a sophisticated type system (generics, covariance and contravariance, etc.) Scala is all of these, but only targets the JVM. F# (and to some extent C#) is most if not all of these, but only targets .NET. What similar language targets the LLVM?

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  • Modify action names for route collections in Symfony?

    - by James Skidmore
    When creating an sfPropelRouteCollection, how can I edit the action names that the collection will generate? For example: # Routing for "product" CRUD product: class: sfPropelRouteCollection options: model: Product module: product actions: [new, create, edit, update, delete] How can I change the actual action that is called for any of the new/create/edit/update/delete methods? I'd like for them to call "ajaxNew," "ajaxCreate," etc. so the URL would look something like "product/ajaxNew", or the action for "update" would be "ajaxUpdate". Let me know if I need to clarify further. Thanks.

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  • Are there public domain collections of translations for strings commonly used in software applicatio

    - by Malcolm
    It seems to me that there must be some public domain collection of gettext compatible PO files that we could search for 1:1 or fuzzy translations for strings commonly used in software applications? Is there a technical and copyright friendly way to query services like Google's Translator Toolkit, LaunchPad, Mygengo, etc. to find translations for common strings? Thank you, Malcolm

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  • ruby class collections

    - by poseid
    how does this work? in irb: >> class A >> b = [1, 2,3] >> end => [1, 2, 3] Is b an instance variable? class variable? how would I access b from outside the class? Is it used for meta-programming?

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  • Using collections/containers/catalogs in Domain Models

    - by devoured elysium
    Let's say I want to model a cinema. The cinema will have a couple of rooms(for example, 7), where the movies are being played. I wonder how should I design the domain model for this scenario. Should the Cinema class concept concept have a direct association with the 7 rooms? Should the Cinema class concept have an association with a catalog of the 7 rooms? Why? I am having some trouble understanding why in some places I see the first case and in some others I see something like the second case. If instead of rooms, I wanted to depict the relationship between Cinema and: Tickets to sell (today). Tickets already sold (today) Customers in the Cinema database The set of hours at which there are movies playing in a given room in the cinema. The set of places you can sit at in a room in the cinema. Should I use catalogs, should I connect them directly to the Cinema concept with a multiplicity of * in the target? Thanks

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  • Immutability of big objects

    - by Malax
    Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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  • NHibernate collections: many-to-many relationships

    - by Brad Heller
    I've got two models, a Product model and a ShoppingCart model. The ShoppingCart model has a collection of products as a property called Products (List). Here is the mapping for my ShoppingCart model. <class name="MyProject.ShoppingCart, MyProject" table="ShoppingCarts"> <id name="Id" column="Id"> <generator class="native" /> </id> <many-to-one name="Company" class="MyProject.Company, MyProject" column="CompanyId" /> <property name="ExternalId" column="GUID" generated="insert" /> <property name="Name" column="Name" /> <property name="Total" column="Total" /> <property name="CreationDate" column="CreationDate" generated="insert" /> <property name="UpdatedDate" column="UpdatedDate" generated="always" /> <bag name="Products" table="ShoppingCartContents" lazy="false"> <key column="ShoppingCartId" /> <many-to-many column="ProductId" class="MyProjectMyProject.Product, MyProject" fetch="join" /> </bag> </class> When I try to save to the DB, the ShoppingCart is saved, but the mapping rows in ShoppingCartContents aren't save, making me thing that there's an issue with the mapping. Where am I going wrong here?

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  • Workaround for abstract attributes in Java

    - by deamon
    In Scala I would write an abstract class with an abstract attribute path: abstract class Base { val path: String } class Sub extends Base { override val path = "/demo/" } Java doesn't know abstract attributes and I wonder what would be the best way to work around this limitation. My ideas: a) constructor parameter abstract class Base { protected String path; protected Base(String path) { this.path = path; } } class Sub extends Base { public Sub() { super("/demo/"); } } b) abstract method abstract class Base { // could be an interface too abstract String getPath(); } class Sub extends Base { public String getPath() { return "/demo/"; } } Which one do you like better? Other ideas? I tend to use the constructor since the path value should not be computed at runtime.

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  • Optional attribute values in MappedField

    - by David Brooks
    I'm new to Scala and Lift, coming from a slightly odd background in PLT Scheme. I've done a quick search on this topic and found lots of questions but no answers. I'm probably looking in the wrong place. I've been working my way through tutorials on using Mapper to create database-backed objects, and I've hit a stumbling block: what types should be used to stored optional attribute values. For example, a simple ToDo object might comprise a title and an optional deadline (e.g. http://rememberthemilk.com). The former would be a MappedString, but the latter could not be a MappedDateTime since the type constraints on the field require, say, defaultValue to return a Date (rather than a Date or null/false/???). Is an underlying NULL handled by the MappedField subclasses? Or are there optional equivalents to things like MappedInt, MappedString, MappedDateTime that allow the value to be NULL in the database? Or am I approaching this in the wrong way?

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  • How to get everything in the string, but a particular pattern

    - by José Leal
    Yet another regexp question: I have a string as the following, "This is a string, and I have a priority !1" So I want to build a regexp that extracts my priority, which is this number 1 preceded by the "!". To extract it is very easy, "!([1-4])". But now I want to extract the text, leaving it out! How can I do that? DETAIL: The !1 can be anywhere in the string, so this is also perfectly fine: "This is a string, !1 and I have a priority" Thanks! UPDATE: I'm using scala

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  • Using UNC path as collections location in Mecurial IIS6 Server2003

    - by Chris M
    I'm running the latest Mercurial and Python 2.6; IIS6 is using the wildcard ISAPI method to attach the site to the Mecurial hgwebdir_wsgi [paths] \ = \\COMP3254\TestRepo\* [web] baseurl = / allow_push = * push_ssl = false style = monoblue The setup works perfectly if I reference the local drive E:\repo* but doesnt work if I specify the network as above; I've given the server (MERCDEV01$) full permissions on the shared folder on COMP3254, I can't think of any other reason it wouldn't work. Any ideas?

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  • where do i put html files in my web-app folder for a lift project with maven?

    - by egervari
    I'm new to Lift framework for scala. For some reason, index.html resides in the web-app directory, and when I start up jetty, http://localhost:8080/ will point to that index.html file just fine. However, if I put a login.html file in the same folder as the index.html, and then go http://localhost:8080/login, Lift does not serve the file. Where do I need to put the files to get them register? I am a little lost because the behaviour only seems to work for index.html and nothing else. This is what happens when I view source in Chrome: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <body>The Requested URL /login was not found on this server</body> </html>

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  • Alternatives to java on android

    - by user84584
    Hello guys, I just got myself an android phone and I'm dying to start coding on it ! However I'm not a big java fan, although I can live with that, I would like to know if there're reasonable alternatives for the android virtual machine. I've done a medium sized project using clojure, however from the reviews I read, it's very slow when running on android. How about scala ? I read that some people did experiments with it in android, is it "fast enough" ? How big is the learning curve ? Cheers, Ze Maria

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  • Passing arguments to anonymous inner classes

    - by synic
    I'm trying to make an API library for our web services, and I'm wondering if it's possible to do something like this: abstract class UserRequest(val userId: Int) { def success(message: String) def error(error: ApiError) } api.invokeRequest(new UserRequest(121) { override def success(message: String) = { // handle success } override def error(error: ApiError) = { // handle the error } } I'm talking about passing parameters to the anonymous inner class, and also overriding the two methods. I'm extremely new to Scala, and I realize my syntax might be completely wrong. I'm just trying to come up with a good design for this library before I start coding it. I'm willing to take suggestions for this, if I'm doing it the completely wrong way, or if there's a better way. The idea is that the API will take some sort of request object, use it to make a request in a thread via http, and when the response has been made, somehow signal back to the caller if the request was a success or an error. The request/error functions have to be executed on the main thread.

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  • Silverlight 4 XAML Collections

    - by mattduffield
    Hello, I have authored some custom classes that I would like to create using XAML: <Grid Width="300" Height="300"> <l:DashboardTable> <l:DashboardTable.DashboardTableQuery> <dq:DashboardTableQuery ConnectionString="Data Source=bunkerhill;Initial Catalog=emgov_data;User Id=emgovadmin;Password=p@$$word;" Query="select datename(month, cr_tb_DateDue) AS Month, sum(cr_tb_AmountTransaction) AS Total from cr_tb_transactionbill where Year(cr_tb_DateDue) = 2005 and Month(cr_tb_DateDue) IN (1,2,3,4) group by datename(month, cr_tb_DateDue)" > <dq:DashboardTableQuery.DataColumns> <dq:DataColumn ColumnName="Month" ColumnOrder="0" Label="Month" /> <dq:DataColumn ColumnName="Total" ColumnOrder="1" Label="Total" /> </dq:DashboardTableQuery.DataColumns> </dq:DashboardTableQuery> </l:DashboardTable.DashboardTableQuery> </l:DashboardTable> </Grid> The problem is that I get a XamlParseException when I try to run this XAML. I have determined it is when it gets to the dq:DataColumn element. It seems like this is only happening when I have a property that then has a collection and then several items in the collection that I am getting this issue. Has any encountered anything similar? I am try to achieve this all in XAML declaratively.

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  • Binding Entity Framework Collections Simply Using ASP.NET MVC

    - by jpcmorton
    To begin with: Using Entity Framework v4.0. ASP.NET MVC 2.0. Visual Studio 2010. I have a model that consists simply of an order & order items. What I want to do is simply bind that model without too much hassle where possible (avoiding type converters, etc). Simply the model looks like this: public class Order { public int ID { get; set; } public string OrderNumber { get; set; } public EntityCollection<OrderItem> Items { get; set; } } public class OrderItem { public int ID { get; set; } public string Qty { get; set; } } This is as simple as I want to keep it. This model is coming directly from the code generated by the entity framework generator. I would prefer to use the model directly from the entity framework (I know there are views saying this is a bad thing, but alas). I then have the View looking like this: <% using (Html.BeginForm()) {%> <%: Html.ValidationSummary(true) %> <fieldset> <legend>Fields</legend> <div class="editor-label"> <%: Html.LabelFor(model => model.ID) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.ID) %> <%: Html.ValidationMessageFor(model => model.ID) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.OrderNumber) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.OrderNumber)%> <%: Html.ValidationMessageFor(model => model.OrderNumber)%> </div> <div id="lineItems"> Where I need to put my line items to be edited, inserted </div> <p> <input type="submit" value="Create" /> </p> </fieldset> <% } %> What I want to do is have a situation where I can use dynamic line items (using javascript). Problems are this: How to go about inserting the initial line item (within the lineItems div). This need to be strongly typed and use the built in validation framework of MVC. Best way to go about inserting line items dynamically so that on the postback there is a complete bind to the model without too much messing around (id = 1,2,3,4, etc). Any help, examples, tips, etc would be appreciated.

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  • Should I use implicit conversions to enforce preconditions?

    - by Malvolio
    It occurs to me that I could use use implicit conversions to both announce and enforce preconditions. Consider this: object NonNegativeDouble { implicit def int2nnd(d : Double) : NonNegativeDouble = new NonNegativeDouble(d) implicit def nnd2int(d : NonNegativeDouble) : Double = d.v def sqrt(n : NonNegativeDouble) : NonNegativeDouble = scala.math.sqrt(n) } class NonNegativeDouble(val v : Double ) { if (v < 0) { throw new IllegalArgumentException("negative value") } } object Test { def t1 = { val d : Double = NonNegativeDouble.sqrt(3.0); printf("%f\n", d); val n : Double = NonNegativeDouble.sqrt(-3.0); } } Ignore for the moment the actual vacuity of the example: my point is, the subclass NonNegativeDouble expresses the notion that a function only takes a subset of the entire range of the class's values. First is this: A good idea, a bad idea, or an obvious idea everybody else already knows about Second, this would be most useful with basic types, like Int and String. Those classes are final, of course, so is there a good way to not only use the restricted type in functions (that's what the second implicit is for) but also delegate to all methods on the underlying value (short of hand-implementing every delegation)?

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  • How to implement a category hierarchy using collections

    - by Luke101
    Hello, I have about 200 categories that are nested. I am currently reading the documention on the C5 generics library. I am not sure if the C5 library is overkill or not. I am looking at converting all my custom algorithms to the C5 implemention. This is what I need. If a certain category is chosen i need to find its parents, siblings, direct children, and all children. This is the way I have it set up. To find the: Parents: I start from the current location then loop through the list and find the current parent. When I find the parent I loop through the whole list again to find the next parent and so on. Siblings: I loop through the whole list and find all the nodes that have the same parent as the choosen node. direct children: I loop through the whole list and find all nodes that is a parent of the choosen node. All Children: This one took me a while to figure out. But I used recursion to find all children of the choosen node. Is there a better way to implement something like this?

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  • How can I get Syslogging to work on the JVM?

    - by Synesso
    I want to do syslogging from Java. There is a log4j appender, but it doesn't seem to work (for me anyway ... though Google results show many others with this issue still unresolved). I'm trying to debug the appender, so I've written the following script based upon RFC3164 It runs, but no logging appears in the syslog. // scala import java.io._ import java.net._ val ds = new DatagramSocket() val fullMsg = "<11>May 26 14:47:22 Hello World" val packet = new DatagramPacket(fullMsg.getBytes("UTF-8"), fullMsg.length, InetAddress.getLocalHost, 514) ds send packet ds.close I also tried using /bin/nc, but it doesn't work either. echo "<14>May 26 15:23:83 Hello world" > nc -u localhost 514 The Ubuntu command /usr/bin/logger does work, however. logger -p user.info hello world # logs: May 26 15:25:10 dsupport2 jem: hello world What could I be doing wrong?

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  • Constructor with non-instance variable assistant?

    - by Robert Fischer
    I have a number of classes that look like this: class Foo(val:BasicData) extends Bar(val) { val helper = new Helper(val) val derived1 = helper.getDerived1Value() val derived2 = helper.getDerived2Value() } ...except that I don't want to hold onto an instance of "helper" beyond the end of the constructor. In Java, I'd do something like this: public class Foo { final Derived derived1, derived2; public Foo(BasicData val) { Helper helper = new Helper(val); derived1 = helper.getDerived1Value(); derived2 = helper.getDerived2Value(); } } So how do I do something like that in Scala? I'm aware of creating a helper object of the same name of the class with an apply method: I was hoping for something slightly more succinct.

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  • How to iterate JPA collections in Google App engine

    - by palto
    Hi I use Google App Engine with datanucleus and JPA. I'm having a real hard time grasping how I'm supposed to read stuff from data store and pass it to JSP. If I load a list of POJOs with entitymanager and pass it to JSP, it crashes to org.datanucleus.exceptions.NucleusUserException: Object Manager has been closed. I understand why this is happening. Obviously because I fetch the list, close the entity manager and pass it to JSP, at which point it will fail because the list is lazy. How do I make the list NOT lazy without resorting to hacks like calling size() or something like that? Here is what I'm trying to do: @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setAttribute("parties", getParties()); RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/WEB-INF/parties.jsp"); dispatcher.forward(req, resp); } private List<Party> getParties(){ EntityManager em = entityManagerProvider.get(); try{ Query query = em.createQuery("SELECT p FROM Party p"); return query.getResultList(); }finally{ em.close(); } }

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  • Fluent / NHibernate Collections of the same class

    - by Charlie Brown
    I am new to NHibernate and I am having trouble mapping the following relationships within this class. public class Category : IAuditable { public virtual int Id { get; set; } public virtual string Name{ get; set; } public virtual Category ParentCategory { get; set; } public virtual IList<Category> SubCategories { get; set; } public Category() { this.Name = string.Empty; this.SubCategories = new List<Category>(); } } Class Maps (although, these are practically guesses) public class CategoryMap : ClassMap<Category> { public CategoryMap() { Id(x => x.Id); Map(x => x.Name); References(x => x.ParentCategory) .Nullable() .Not.LazyLoad(); HasMany(x => x.SubCategories) .Cascade.All(); } } Each Category may have a parent category, some Categories have many subCategories, etc, etc I can get the Category to Save correctly (correct subcategories and parent category fk exist in the database) but when loading, it returns itself as the parent category. I am using Fluent for the class mapping, but if someone could point me in the right direction for just plain NHibernate that would work as well.

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  • Running a method after the constructor of any derived class

    - by Alexey Romanov
    Let's say I have a Java class abstract class Base { abstract void init(); ... } and I know every derived class will have to call init() after it's constructed. I could, of course, simply call it in the derived classes' constructors: class Derived1 extends Base { Derived1() { ... init(); } } class Derived2 extends Base { Derived2() { ... init(); } } but this breaks "don't repeat yourself" principle rather badly (and there are going to be many subclasses of Base). Of course, the init() call can't go into the Base() constructor, since it would be executed too early. Any ideas how to bypass this problem? I would be quite happy to see a Scala solution, too.

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