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• iPhone Development - CoreData runtime error

  - by Mustafa

  I'm facing a strange CoreData issue. Here's the log: 2010-04-07 15:59:36.913 MyProject[263:207] <MyEntity: 0x180370> (entity: MyEntity; id: 0x17e890 <x-coredata://0F55C533-41BD-4F09-9CCA-0CB304CAB065/MyEntity/p380> ; data: <fault>) 2010-04-07 15:59:36.918 MyProject[263:207] *** Terminating app due to uncaught exception 'NSObjectInaccessibleException', reason: 'The NSManagedObject with ID:0x17e890 <x-coredata://0F55C533-41BD-4F09-9CCA-0CB304CAB065/MyEntity/p380> has been invalidated.' I have a hierarchy of UITableViewControllers that use NSFetchedResultsController to populate the table, and when a particular row is selected, the detail view is shown. UITableView (MyMainEntity) UITableView (MyEntity) UITableView (MyEntity) detail view Both MyMainEntity UITableView and MyEntity UITableView use NSFetchedResultsController to show the records. Sometimes it crashes when i'm scrolling the tableView, and sometimes it crashes when i try to open the detail view. I can navigate to the MyEntity detail view multiple times before application crashes. What does this error mean? and how can i fix it!?

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• C++ compiler unable to find function (namespace related)

  - by CS student

  I'm working in Visual Studio 2008 on a C++ programming assignment. We were supplied with files that define the following namespace hierarchy (the names are just for the sake of this post, I know "namespace XYZ-NAMESPACE" is redundant): (MAIN-NAMESPACE){ a bunch of functions/classes I need to implement... (EXCEPTIONS-NAMESPACE){ a bunch of exceptions } (POINTER-COLLECTIONS-NAMESPACE){ Set and LinkedList classes, plus iterators } } The MAIN-NAMESPACE contents are split between a bunch of files, and for some reason which I don't understand the operator<< for both Set and LinkedList is entirely outside of the MAIN-NAMESPACE (but within Set and LinkedList's header file). Here's the Set version: template<typename T> std::ostream& operator<<(std::ostream& os, const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set<T>& set) Now here's the problem: I have the following data structure: Set A Set B Set C double num It's defined to be in a class within MAIN-NAMESPACE. When I create an instance of the class, and try to print one of the sets, it tells me that: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set' (or there is no acceptable conversion) However, if I just write a main() function, and create Set A, fill it up, and use the operator- it works. Any idea what is the problem? (note: I tried any combination of using and include I could think of).

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• How come the Actionscript 3 ENTER_FRAME event is crazy nuts?

  - by nstory

  So, I've been toying around with Flash, browsing through the documentation, and all that, and noticed that the ENTER_FRAME event seems to defy my expectation of a deterministic universe. Take the following example: (new MovieClip()).addEventListener(Event.ENTER_FRAME, function(ev) {trace("Test");}); Notice this anonymous MovieClip is not added to the display hierarchy, and any reference to it is immediately lost. It will actually print "Test" once a frame until it is garbage collected. How insane is that? The behavior of this is actually determined by when the garbage collector feels like coming around in all its unpredictable insanity! Is there a better way to create intermittent failures? Seriously. My two theories are that either the DisplayObject class stores weak references to all its instances for the purpose of dispatching ENTER_FRAME events, or, and much wilder, the Flash player actually scans the heap each frame looking for ENTER_FRAME listeners to pull on. Can any hardened Actionscript developer clue me in on how this works? (And maybe a why - the - f**k they thought this was a good idea?)

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• How does object of sub-class record information about its super-class the in a Virtual Inheritance

  - by Summer_More_More_Tea

  Hi there: I encounter this problem when tackling with virtual inheritance. I remember that in a non-virtual inheritance hierarchy, object of sub-class hold an object of its direct super-class. What about virtual inheritance? In this situation, does object of sub-class hold an object of its super-class directly or just hold a pointer pointing to an object of its super-class? By the way, why the output of the following code is: sizeof(A): 8 sizeof(B): 20 sizeof(C): 32 Code: #include <iostream> using namespace std; class A{ char k[ 3 ]; public: virtual void a(){}; }; class B : public virtual A{ char j[ 3 ]; public: virtual void b(){}; }; class C : public virtual B{ char i[ 3 ]; public: virtual void c(){}; }; int main( int argc, char *argv[] ){ cout << "sizeof(A): " << sizeof( A ) << endl; cout << "sizeof(B): " << sizeof( B ) << endl; cout << "sizeof(C): " << sizeof( C ) << endl; return 0; } Thanks in advance. Kind regards.

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• Sorting by some field and fetching whole tree from DB

  - by Niaxon

  Hello everyone, I am trying to do file browser in a tree form and have a problem to sort it somehow. I use PHP and MySQL for that. I've created mixed (nested set + adjacency) table 'element' with the following fields: element_id, left_key, right_key, level, parent_id, element_name, element_type (enum: 'folder','file'), element_size. Let's not discuss right now that it is better to move information about element (name, type, size) into other table. Function to scan specified directory and fill table work correctly. Noteworthy, i am adding elements to tree in specific order: folders first and only files. After that i can easily fetch and display whole table on the page using simple query: SELECT * FROM element WHERE 1=1 ORDER BY left_key With the result of that query and another function i can generate correct html code (<ul><li>... and so on). Now back to the question (finally, huh?). I am struggling to add sorting functionality. For example i want to order my result by size. Here i need to keep in my mind whole hierarchy of tree and rule: folders first, files later. I believe i can do that by generating in PHP recursive query: SELECT * FROM element WHERE parent_id = {$parentId} ORDER BY element_type (so folders would be first), size (or name for example) After that for each result which is folder i will send another query to get it's content. Also it's possible to fetch whole tree by left_key and after that sort it in PHP as array but i guess that would be worse :) I wonder if there is better and more efficient way to do such thing?

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• PHP extend a class method that is called from another class which extends it and calls the method wi

  - by dan.codes

  I am trying to extend a class and override one of its methods. lets call that class A. My class, class B, is overiding a protected method. Class C extends class A and Class D extends class C. Inside of Class D, the method I am trying to overwrite is also extended here and that calls parent::mymethodimoverriding. That method does not exist in class C so it goes to it in class A. That is the method I am overiding in class B and obviously you can't extend A with B and have those changes show up in D since it does not fall in line with the class hierarchy. I might be wrong, so correct me please. so if my class b is called and ran then class D gets called it runs the method in A and overwrites what I had set. I am thinking there must be a way to get this to work, I am just missing something. here is an example, as you can see in class A there is a call to setTitle and it is set to "Example" In my class I set it to "NewExample". My class is getting called before class D so when class D is called it goes back to the parent and sets the title back to "Example" class A{ protected function _thefunction(){ setTitle("Example"); } } class B extends A{ protected function _thefunction(){ My new code here setTitle("NewExample"); } } class C extends A{ nothing that matters in here for what I am doing } class D extends C{ protected function _thefunction(){ parent::_thefunction(); additional code here } }

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• Map inheritance from generic class in Linq To SQL

  - by Ksenia Mukhortova

  Hi everyone, I'm trying to map my inheritance hierarchy to DB using Linq to SQL: Inheritance is like this, classes are POCO, without any LINQ to SQL attributes: public interface IStage { ... } public abstract class SimpleStage<T> : IStage where T : Process { ... } public class ConcreteStage : SimpleStage<ConcreteProcess> { ... } Here is the mapping: <Database Name="NNN" xmlns="http://schemas.microsoft.com/linqtosql/mapping/2007"> <Table Name="dbo.Stage" Member="Stage"> <Type Name="BusinessLogic.Domain.IStage"> <Column Name="ID" Member="ID" DbType="Int NOT NULL IDENTITY" IsPrimaryKey="true" IsDbGenerated="true" AutoSync="OnInsert" /> <Column Name="StageType" Member="StageType" IsDiscriminator="true" /> <Type Name="BusinessLogic.Domain.SimpleStage" IsInheritanceDefault="true"> <Type Name="BusinessLogic.Domain.ConcreteStage" IsInheritanceDefault="true" InheritanceCode="1"/> </Type> </Type> </Table> </Database> In the runtime I get error: System.InvalidOperationException was unhandled Message="Mapping Problem: Cannot find runtime type for type mapping 'BusinessLogic.Domain.SimpleStage'." Neither specifying SimpleStage, nor SimpleStage<T> in mapping file helps - runtime keeps producing different types of errors. DC is created like this: StreamReader sr = new StreamReader(@"MappingFile.map"); XmlMappingSource mapping = XmlMappingSource.FromStream(sr.BaseStream); DataContext dc = new DataContext(@"connection string", mapping); If Linq to SQL doesn't support this, could you, please, advise some other ORM, which does. Thanks in advance, Regards! Ksenia

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• Comparing objects and inheritance

  - by ereOn

  Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.

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• Custom Android layout that handles its children

  - by Gromix

  Hi, I'm trying to create a custom Android control to emulate a LinearLayout with a fancier display. Basically, I want the exact behaviour of a LinearLayout, but also borders, a background, ... I could do it all in XML (works great) but since I have dozens of occurences in my app it's getting hard to maintain. I thought it would be nicer to have something like this: /* Main.xml */ <MyFancyLayout> <TextView /> <ImageView /> </MyfancyLayout> My problem is, I don't want to have to re-write LinearLayout, so is there a way to only change its appearance? I got as far as this, which doesn't work... can anyone think of a better approach? /* MyFancyLayout.xml */ <merge> ... the complex hierarchy to make it look like what I want ... with background attributes etc </merge> and /* MyFancyLayout.java */ public class MyFancyLayout extends LinearLayout { // inflate the XML // move all the real children (as given by main.xml) to the inflated layout // do I still need to override onMeasure and onLayout? } Cheers! Romain

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• What's the "correct way" to organize this project?

  - by user571747

  I'm working on a project that allows multiple users to submit large data files and perform operations on them. The "backend" which performs these operations is written in Perl while the "frontend" uses PHP to load HTML template files and determines which content to deliver. Data is stored in a database (MySQL, SQLite, Oracle) and while there is data which has not yet been acted upon, Perl adds it to a running queue which delivers data to other threads based on system load. In addition, there may be pre- and post-processing of the data before and after the main Perl script operates (the specifications are unclear) so I may want to allow these processors to be user-selectable plugins. I had been writing this project in a more procedural fashion but I am quickly realizing the benefit of separating concerns as to limit the scope one change has on the rest of the project. I'm quite unexperienced with design patterns and am curious what the best way to proceed is. I've heard MVC thrown around quite a bit but I am unsure of how to apply it. Specifically, what are some good options to structure this code (in terms of design patterns and folder hierarchy)? How can I achieve this with both PHP and Perl while minimizing duplicated code between languages? Should I keep my PHP files in the top level so I don't have ugly paths in the URL? Also, if I want to provide interchangeable databases, does each table need its own DAO implementation?

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• Is there a proper and wrong way to format CSS?

  - by DavidR

  When I first started writing CSS, I was writing it in an expanded form div.class { margin: 10px 5px 3px; border: 1px solid #333; font-weight: bold; } .class .subclass { text-align:right; } but now I find myself writing css like this: (Example from code I'm actually writing now) .object1 {} .scrollButton{width:44px;height:135px;} .scrollButton img {padding:51px 0 0 23px;} .object2 {width:165px;height:94px;margin:15px 0 0 23px;padding:15px 0 0 10px;background:#fff;} .featuredObject .symbol{line-height:30px; padding-top:6px;} .featuredObject .value {width:90px;} .featuredObject .valueChange {padding:5px 0 0 0;} .featuredObject img {position:absolute;margin:32px 0 0 107px;} and I'm beginning to worry because a lot of the time I see the first form done in examples online, while I find the second form a lot easier for me to work with. It has a lower vertical height, so I can see all the classes at a glance with less scrolling, the tabulation of the hierarchy seems more apparent, and it looks more like code I'd write with javascript or html. Is this a valid way of doing code, or to keep with standards when putting it online should I use the vertical form instead?

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• Mixing together Connect by, inner join and sum with Oracle

  - by François

  Hey there, I need help with a oracle query. Excuse me in advance for my english. Here is my setup: I have 2 tables called respectively "tasks" and "timesheets". The "tasks" table is a recursive one, that way each task can have multiple subtasks. Each timesheet is associated with a task (not necessarily the "root" task) and contains the number of hours worked on it. Example: Tasks id:1 | name: Task A | parent_id: NULL id:2 | name: Task A1 | parent_id: 1 id:3 | name: Task A1.1 | parent_id: 2 id:4 | name: Task B | parent_id: NULL id:5 | name: Task B1 | parent_id: 4 Timesheets id:1 | task_id: 1 | hours: 1 id:2 | task_id: 2 | hours: 3 id:3 | task_id:3 | hours: 1 id:5 | task_id:5 | hours:1 ... What I want to do: I want a query that will return the sum of all the hours worked on a "task hierarchy". If we take a look at the previous example, It means I would like to have the following results: task A - 5 hour(s) | task B - 1 hour(s) At first I tried this SELECT TaskName, Sum(Hours) "TotalHours" FROM ( SELECT replace(sys_connect_by_path(decode(level, 1, t.name), '~'), '~') As TaskName, ts.hours as hours FROM tasks t INNER JOIN timesheets ts ON t.id=ts.task_id START WITH PARENTOID=-1 CONNECT BY PRIOR t.id = t.parent_id ) GROUP BY TaskName Having Sum(Hours) > 0 ORDER BY TaskName And it almost work. THe only problem is that if there are no timesheet for a root task, it will skip the whole hieararchy... but there might be timesheets for the child rows and it is exactly what happens with Task B1. I know it is the "inner join" part that is causing my problem but I'm not sure how can I get rid of it. Any idea how to solve this problem? Thank you

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• What is an appropriate way to separate lifecycle events in the logging system?

  - by Hanno Fietz

  I have an application with many different parts, it runs on OSGi, so there's the bundle lifecycles, there's a number of message processors and plugin components that all can die, can be started and stopped, have their setup changed etc. I want a way to get a good picture of the current system status, what components are up, which have problems, how long they have been running for etc. I think that logging, especially in combination with custom appenders (I'm using log4j), is a good part of the solution and does help ad-hoc analysis as well as live monitoring. Normally, I would classify lifecycle events as INFO level, but what I really want is to have them separate from what else is going on in INFO. I could create my own level, LIFECYCLE. The lifecycle events happen in various different areas and on various levels in the application hierarchy, also they happen in the same areas as other events that I want to separate them from. I could introduce some common lifecycle management and use that to distinguish the events from others. For instance, all components that have a lifecycle could implement a particular interface and I log by its name. Are there good examples of how this is done elsewhere? What are considerations?

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• Entity Framework does not map 2 columns from a SqlQuery calling a stored procedure

  - by user1783530

  I'm using Code First and am trying to call a stored procedure and have it map to one of my classes. I created a stored procedure, BOMComponentChild, that returns details of a Component with information of its hierarchy in PartsPath and MyPath. I have a class for the output of this stored procedure. I'm having an issue where everything except the two columns, PartsPath and MyPath, are being mapped correctly with these two properties ending up as Nothing. I searched around and from my understanding the mapping bypasses any Entity Framework name mapping and uses column name to property name. The names are the same and I'm not sure why it is only these two columns. The last part of the stored procedure is: SELECT t.ParentID ,t.ComponentID ,c.PartNumber ,t.PartsPath ,t.MyPath ,t.Layer ,c.[Description] ,loc.LocationID ,loc.LocationName ,CASE WHEN sup.SupplierID IS NULL THEN 1 ELSE sup.SupplierID END AS SupplierID ,CASE WHEN sup.SupplierName IS NULL THEN 'Scinomix' ELSE sup.SupplierName END AS SupplierName ,c.Active ,c.QA ,c.IsAssembly ,c.IsPurchasable ,c.IsMachined ,t.QtyRequired ,t.TotalQty FROM BuildProducts t INNER JOIN [dbo].[BOMComponent] c ON c.ComponentID = t.ComponentID LEFT JOIN [dbo].[BOMSupplier] bsup ON bsup.ComponentID = t.ComponentID AND bsup.IsDefault = 1 LEFT JOIN [dbo].[LookupSupplier] sup ON sup.SupplierID = bsup.SupplierID LEFT JOIN [dbo].[LookupLocation] loc ON loc.LocationID = c.LocationID WHERE (@IsAssembly IS NULL OR IsAssembly = @IsAssembly) ORDER BY t.MyPath and the class it maps to is: Public Class BOMComponentChild Public Property ParentID As Nullable(Of Integer) Public Property ComponentID As Integer Public Property PartNumber As String Public Property MyPath As String Public Property PartsPath As String Public Property Layer As Integer Public Property Description As String Public Property LocationID As Integer Public Property LocationName As String Public Property SupplierID As Integer Public Property SupplierName As String Public Property Active As Boolean Public Property QA As Boolean Public Property IsAssembly As Boolean Public Property IsPurchasable As Boolean Public Property IsMachined As Boolean Public Property QtyRequired As Integer Public Property TotalQty As Integer Public Property Children As IDictionary(Of String, BOMComponentChild) = New Dictionary(Of String, BOMComponentChild) End Class I am trying to call it like this: Me.Database.SqlQuery(Of BOMComponentChild)("EXEC [BOMComponentChild] @ComponentID, @PathPrefix, @IsAssembly", params).ToList() When I run the stored procedure in management studio, the columns are correct and not null. I just can't figure out why these won't map as they are the important information in the stored procedure. The types for PartsPath and MyPath are varchar(50).

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• C# xml serializer - serialize derived objects

  - by gln

  Hi, I want to serialize the following: [Serializable] [DefaultPropertyAttribute("Name")] [XmlInclude(typeof(ItemInfo))] [XmlInclude(typeof(ItemInfoA))] [XmlInclude(typeof(ItemInfoB))] public class ItemInfo { private string name; [XmlArray("Items"), XmlArrayItem(typeof(ItemInfo))] private ArrayList arr; private ItemInfo parentItemInfo; } [Serializable] [XmlInclude(typeof(ItemInfo))] [XmlInclude(typeof(ItemInfoA))] [XmlInclude(typeof(ItemInfoB))] public class ItemInfoA : ItemInfo { ... } [Serializable] [XmlInclude(typeof(ItemInfo))] [XmlInclude(typeof(ItemInfoA))] [XmlInclude(typeof(ItemInfoB))] public class ItemInfoB : ItemInfo { ... } The class itemInfo describes a container which can hold other itemInfo objects in the array list, the parentItemInfo describes which is the parent container of the item info. Since ItemInfoA and ItemInfoB derive from ItemInfo they can also be a member of the array list and the parentItemInfo, therefore when trying to serialize these objects (which can hold many objects in hierarchy) it fails with exception can't generate the xml file - innerexception. My question is: What attributes do I need to add the ItemInfo class so it will be serializable? Note: the exception is only when the ItemInfo[A]/[B] are initialized with parentItemInfo or the arrayList. Help please! Thanks!

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• CSS file in a Spring WAR returns a 404

  - by Rachel G.

  I have a J2EE application that I am building with Spring and Maven. It has the usual project structure. Here is a bit of the hierarchy. MyApplication src main webapp WEB-INF layout header.jsp styles main.css I want to include that CSS file in my JSP. I have the following tag in place. <c:url var="styleSheetUrl" value="/styles/main.css" /> <link rel="stylesheet" href="${styleSheetUrl}"> When I deploy the application, the CSS page isn't being located. When I view the page source, the href is /MyApplication/styles/main.css. Looking inside the WAR, there is a /styles/main.css. However, I get a 404 when I try to access the CSS file directly in the browser. I discovered that the reason for the issue was the Dispatcher Servlet mapping. The mapping looks as follows. <servlet-mapping> <servlet-name>Spring MVC Dispatcher Servlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> I imagine the Dispatcher Servlet doesn't know how to handle the CSS request. What is the best way to handle this issue? I would rather not have to change all of my request mappings.

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• Calling an Overridden Method from a Parent-Class Constructor

  - by Vaibhav Bajpai

  I tried calling an overridden method from a constructor of a parent class and noticed different behavior across languages. C++ - echoes A.foo() class A{ public: A(){foo();} virtual void foo(){cout<<"A.foo()";} }; class B : public A{ public: B(){} void foo(){cout<<"B.foo()";} }; int main(){ B *b = new B(); } Java - echoes B.foo() class A{ public A(){foo();} public void foo(){System.out.println("A.foo()");} } class B extends A{ public void foo(){System.out.println("B.foo()");} } class Demo{ public static void main(String args[]){ B b = new B(); } } C# - echoes B.foo() class A{ public A(){foo();} public virtual void foo(){Console.WriteLine("A.foo()");} } class B : A{ public override void foo(){Console.WriteLine("B.foo()");} } class MainClass { public static void Main (string[] args) { B b = new B(); } } I realize that in C++ objects are created from top-most parent going down the hierarchy, so when the constructor calls the overridden method, B does not even exist, so it calls the A' version of the method. However, I am not sure why I am getting different behavior in Java and C#.

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• XSLT; parse escaped text to a node-set and extract subelements

  - by Tom W

  Hello SO; I've been fighting with this problem all day and am just about at my wit's end. I have an XML file in which certain portions of data are stored as escaped text but are themselves well-formed XML. I want to convert the whole hierarchy in this text node to a node-set and extract the data therein. No combination of variables and functions I can think of works. The way I'd expect it to work would be: <xsl:variable name="a" select="InnerXML"> <xsl:for-each select="exsl:node-set($a)/*"> 'do something </xsl:for-each> The input element InnerXML contains text of the form <root><element a>text</element a><element b><element c/><element d>text</element d></element b></root> but that doesn't really matter. I just want to navigate the xml like a normal node-set. Where am I going wrong?

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• LayoutInflater ignoring parameters ?

  - by TiGer

  Hi, I have the following xml object representing a ImageButton <?xml version="1.0" encoding="utf-8"?> <ImageButton xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/genreCellItemId" android:layout_weight="1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:paddingLeft="5.0dip" android:paddingRight="5.0dip"> </ImageButton> I try to inflate it and add it to a TableRow with the following code : LayoutInflater inflater= this.getLayoutInflater(); TableLayout grid = (TableLayout)findViewById(R.id.bodyTableLayout); TableRow row = (TableRow)inflater.inflate(R.layout.genre_row, null); View myButton = (View)inflater.inflate(R.layout.genre_cell, null); row.addView(tempButton, new TableRow.LayoutParams()); grid.addView(row, new TableLayout.LayoutParams()); Ok so I noticed that it didn't look as expected, so I fire up the Hierarchy Viewere and noticed that the ImageButton's actually have an layout_width = FILL_PARENT instead of WRAP_CONTENT, also the layout_gravity is NONE and there is no padding to be seen... Do, am I inflating it wrongly ? Or is maybe the new TableRow.LayoutParams() part doins omething wrong ?

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• Why aren't Java's generics implicitly polymorphic?

  - by froadie

  I'm a bit confused about how Java generics handle inheritance / polymorphism. Assume the following hierarchy - Animal (Parent) Dog - Cat (Children) So suppose I have a method doSomething(List<Animal> animals). By all the rules of inheritance and polymorphism, I would assume that a List<Dog> is a List<Animal> and a List<Cat> is a List<Animal> - and so either one could be passed to this method. Not so. If I want to achieve this behavior, I have to explicitly tell the method to accept a list of any subset of Animal by saying doSomething(List<? extends Animal> animals). I understand that this is Java's behavior. My question is why? Why is polymorphism generally implicit, but when it comes to generics it must be specified?

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• Extending abstract classes in c#

  - by ng

  I am a Java developer and I have noticed some differences in extending abstract classes in c# as opposed to Java. I was wondering how a c# developer would achived the following. 1) Covarience public abstract class A { public abstract List<B> List(); } public class BList : List<T> where T : B { } public abstract class C : A { public abstract BList List(); } So in the above hierarchy, there is covarience in C where it returns a type compatible with what A returns. However this gives me an error in Visual Studio. Is there a way to specify a covarient return type in c#? 2) Adding a setter to a property public abstract class A { public abstract String Name { get; } } public abstract class B : A { public abstract String Name { get; set } } Here the compiler complains of hiding. Any suggestions? Please do not suggest using interfaces unless that is the ONLY way to do this.

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• How costly performance-wise are these actions in iPhone objective-C?

  - by Alex Gosselin

  This is really a few questions in one, I'm wondering what the performance cost is for these things, as I haven't really been following a best practice of any sort for these. The answers may also be useful to other readers, if somebody knows these. (1) If I need the core data managed object context, is it bad to use #import "myAppDelegate.h" //farther down in the code: NSManagedObjectContext *context = [(myAppDelegate.h*)[[UIApplication sharedApplication] delegate] managedObjectContext]; as opposed to leaving the warning you get if you don't cast the delegate? (2) What is the cheapest way to hard-code a string? I have been using return @"myString"; on occasion in some functions where I need to pass it to a variety of places, is it better to do it this way: static NSString *str = @"myString"; return str; (3) How costly is it to subclass an object i wrote vs. making a new one, in general? (4) When I am using core data and navigating through a hierarchy of some sort, is it necessary to turn things back into faults somehow after I read some info from them? or is this done automatically? Thanks for any help.

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• Monotouch auto resizing views in iphone

  - by Tim Bassett

  I have created a view in interface builder that contains another view (content area) and a button bar at the bottom. The hierarchy is as: ->View --->mapContainer UIView ----->map MKMapView ----->OverlayView UIView --->ToolBar UIToolBar I would like the mapContainer to resize to full window when the ToolBar is hidden. I would like the map and the OverlayView to resize to the mapContainer size I have attempted the following code, but it has no effect. Please advise? public override void ViewDidLoad () { base.ViewDidLoad (); this.mapContainer.AutosizesSubviews = true ; this.View.AutosizesSubviews = true ; try { this.mapContainer.AutoresizingMask = UIViewAutoresizing.FlexibleHeight | UIViewAutoresizing.FlexibleWidth ; this.map.AutoresizingMask = UIViewAutoresizing.FlexibleHeight | UIViewAutoresizing.FlexibleWidth ; this.map.SizeToFit(); this.mapContainer.SizeToFit(); this.map.SizeToFit(); this.View.Frame = new System.Drawing.RectangleF(0,0,this.View.Frame.Width, this.View.Frame.Height ); this.mapContainer.LayoutSubviews(); } catch(Exception ex) { Console.Write(ex.ToString()); } }

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• Event-based interaction between two custom classes

  - by Antenka

  Hello everybody. I have such problem: I have 2 custom components, which have their own nesting hierarchy ... One is container for another. I have to "familiarize them" with each other. The way I'm trying to achieve that is using global events (one side is firing and the other one is catching): Application.application.addEventListener("Hello", function (data:Event):void{ // .. some actions }); //and Application.application.dispatchEvent(new Event(Hello)); Everything is pretty good, but there's one thingy .. when I'm trying to catch the event, I can't access the class, who is catching it. E.g.: Container fires the event. Child caughts it. Then should be created the connection between container and it's child. BUT, the only thing I could acheive is passing a reference to the Container in the DynamicEvent. Is there any chance that I could access the child at the event-handler function. Or maybe there's more elegant way to solve this problem ... Any help would be greately appreciated :)

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• Suggestions on Working with this Inherited Generic Method

  - by blu

  We have inherited a project that is a wrapper around a section of the core business model. There is one method that takes a generic, finds items matching that type from a member and then returns a list of that type. public List<T> GetFoos<T>() { List<IFoo> matches = Foos.FindAll( f => f.GetType() == typeof(T) ); List<T> resultList = new List<T>(); foreach (var match in matches) { resultList.Add((T)obj); } } Foos can hold the same object cast into various classes in inheritance hierarchy to aggregate totals differently for different UI presentations. There are 20+ different types of descendants that can be returned by GetFoos. The existing code basically has a big switch statement copied and pasted throughout the code. The code in each section calls GetFoos with its corresponding type. We are currently refactoring that into one consolidated area, but as we are doing that we are looking at other ways to work with this method. One thought was to use reflection to pass in the type, and that worked great until we realized the Invoke returned an object, and that it needed to be cast somehow to the List <T>. Another was to just use the switch statement until 4.0 and then use the dynamic language options. We welcome any alternate thoughts on how we can work with this method. I have left the code pretty brief, but if you'd like to know any additional details please just ask.

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