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• Is there any Inheritance problem with <table> and it's elements, like <form> elements?

  - by metal-gear-solid

  Is there any Inheritance problem with <table>, tr th td tbody thead tfoot also like form elements? In IE 6+ and FF 3+ with Strict doctype. Tables also have inheritance turned off in some browsers. You may notice that in some browsers, your tables’ text will be larger, clunkier and not so pretty. This is also due to inheritance. Many browsers give tables their own style. It's mentioned here http://www.komodomedia.com/blog/2006/10/css-trickery-part-5-inheritance/ For which browsers author is talking about, it's not mentioned I tested on FF 3.6 and IE7 but unable to find is there any issue. I just wanted to be sure before adding this in my CSS reset. Do i really need this? table { font-family:inherit; font-size:inherit; font-weight:inherit; }

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• Subclassed django models with integrated querysets

  - by outofculture

  Like in this question, except I want to be able to have querysets that return a mixed body of objects: >>> Product.objects.all() [<SimpleProduct: ...>, <OtherProduct: ...>, <BlueProduct: ...>, ...] I figured out that I can't just set Product.Meta.abstract to true or otherwise just OR together querysets of differing objects. Fine, but these are all subclasses of a common class, so if I leave their superclass as non-abstract I should be happy, so long as I can get its manager to return objects of the proper class. The query code in django does its thing, and just makes calls to Product(). Sounds easy enough, except it blows up when I override Product.__new__, I'm guessing because of the __metaclass__ in Model... Here's non-django code that behaves pretty much how I want it: class Top(object): _counter = 0 def __init__(self, arg): Top._counter += 1 print "Top#__init__(%s) called %d times" % (arg, Top._counter) class A(Top): def __new__(cls, *args, **kwargs): if cls is A and len(args) > 0: if args[0] is B.fav: return B(*args, **kwargs) elif args[0] is C.fav: return C(*args, **kwargs) else: print "PRETENDING TO BE ABSTRACT" return None # or raise? else: return super(A).__new__(cls, *args, **kwargs) class B(A): fav = 1 class C(A): fav = 2 A(0) # => None A(1) # => <B object> A(2) # => <C object> But that fails if I inherit from django.db.models.Model instead of object: File "/home/martin/beehive/apps/hello_world/models.py", line 50, in <module> A(0) TypeError: unbound method __new__() must be called with A instance as first argument (got ModelBase instance instead) Which is a notably crappy backtrace; I can't step into the frame of my __new__ code in the debugger, either. I have variously tried super(A, cls), Top, super(A, A), and all of the above in combination with passing cls in as the first argument to __new__, all to no avail. Why is this kicking me so hard? Do I have to figure out django's metaclasses to be able to fix this or is there a better way to accomplish my ends?

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• Best way to re-use the same django models and admin for multiple apps

  - by kepioo

  Given a reference app ( called guide), how can I create additional apps that will reuse the same model/admin/views than guide - the motivation behind is to be able to individually control each subapp. guide guideApp1 exact same models/admin/views than guide guideApp2 exact same models/admin/views than guide in the Admin site, I should have : 1 section for guideApp1 with all the tables defined in guide, that applies to guideApp1 1 section for guideApp12 with all the tables defined in guide, that applies to guideApp2

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• How to force multiple Interfaces to include certain the same properties?

  - by Jed

  I am trying to figure out a way to force all of my Interfaces to include properties of the same name/type. For example: I have two Interfaces; IGetAlarms and IGetDiagnostics. Each of the Interfaces will contain properties that are specific to the Interface itself, however I want to force the two Interfaces (and all other Interfaces that may be added later) to include properties of the same name. So, the result may look something like the this: interface IGetAlarms { string GetAlarms(); DateTime LastRuntime { get; set; } } interface IGetDiagnostics { string GetDiagnostics(); DateTime LastRuntime { get; set; } } Notice that both Interfaces include a DateTime property named LastRuntime. I would like to know if there is some way I can force other Interfaces that will be added later to include the DateTime LastRuntime property. I have naively attempted to have all my Interfaces implement another Interface (IService) - which includes the LastRuntime property. However, that doesn't solve my problem as that simply forces the class to implement the property - not all the Interfaces. Thanks.

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• mongo mapper with STI with more than one type?

  - by holden

  I have a series of models all which inherit from a base model Properties For example Bars, Restaurants, Cafes, etc. class Property include MongoMapper::Document key :name, String key :_type, String end class Bar < Property What I'm wondering is what to do with the case when a record happens to be both a Bar & a Restaurant? Is there a way for a single object to inherit the attributes of both models? And how would it work with the key :_type?

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• Populating Models from other Models in Django?

  - by JT

  This is somewhat related to the question posed in this question but I'm trying to do this with an abstract base class. For the purposes of this example lets use these models: class Comic(models.Model): name = models.CharField(max_length=20) desc = models.CharField(max_length=100) volume = models.IntegerField() ... <50 other things that make up a Comic> class Meta: abstract = True class InkedComic(Comic): lines = models.IntegerField() class ColoredComic(Comic): colored = models.BooleanField(default=False) In the view lets say we get a reference to an InkedComic id since the tracer, err I mean, inker is done drawing the lines and it's time to add color. Once the view has added all the color we want to save a ColoredComic to the db. Obviously we could do inked = InkedComic.object.get(pk=ink_id) colored = ColoredComic() colored.name = inked.name etc, etc. But really it'd be nice to do: colored = ColoredComic(inked_comic=inked) colored.colored = True colored.save() I tried to do class ColoredComic(Comic): colored = models.BooleanField(default=False) def __init__(self, inked_comic = False, *args, **kwargs): super(ColoredComic, self).__init__(*args, **kwargs) if inked_comic: self.__dict__.update(inked_comic.__dict__) self.__dict__.update({'id': None}) # Remove pk field value but it turns out the ColoredComic.objects.get(pk=1) call sticks the pk into the inked_comic keyword, which is obviously not intended. (and actually results in a int does not have a dict exception) My brain is fried at this point, am I missing something obvious, or is there a better way to do this?

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• printing in the same line in java.

  - by sil3nt

  Hi there, I have a base class called Items and 3 derived classes, and within the Items base class i have a print function of the form public void print(){ System.out.println("ID " + id + " Title " + title + " <" + year + "> "); } and within every derived class I call the Items print function through super.print(); which is followed by a specific print function relating to the derived class. My problem is, whenever the printing is executed from one of the derived classes the printed text is not on the same line. So super.print() will be in the line above the derived class print function. How do I get them both to be on the same line?

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• How does a template class inherit another template class?

  - by hkBattousai

  I have a "SquareMatrix" template class which inherits "Matrix" template class, like below: SquareMatrix.h: #ifndef SQUAREMATRIX_H #define SQUAREMATRIX_H #include "Matrix.h" template <class T> class SquareMatrix : public Matrix<T> { public: T GetDeterminant(); }; template <class T> // line 49 T SquareMatrix<T>::GetDeterminant() { T t = 0; // Error: Identifier "T" is undefined // line 52 return t; // Error: Expected a declaration // line 53 } // Error: Expected a declaration // line 54 #endif I commented out all other lines, the files contents are exactly as above. I receive these error messages: LINE 49: IntelliSense: expected a declaration LINE 52: IntelliSense: expected a declaration LINE 53: IntelliSense: expected a declaration LINE 54: error C2039: 'GetDeterminant' : is not a member of 'SquareMatrix' LINE 54: IntelliSense: expected a declaration So, what is the correct way of inheriting a template class? And what is wrong with this code? The "Matrix" class: template <class T> class Matrix { public: Matrix(uint64_t unNumRows = 0, uint64_t unNumCols = 0); void GetDimensions(uint64_t & unNumRows, uint64_t & unNumCols) const; std::pair<uint64_t, uint64_t> GetDimensions() const; void SetDimensions(uint64_t unNumRows, uint64_t unNumCols); void SetDimensions(std::pair<uint64_t, uint64_t> Dimensions); uint64_t GetRowSize(); uint64_t GetColSize(); void SetElement(T dbElement, uint64_t unRow, uint64_t unCol); T & GetElement(uint64_t unRow, uint64_t unCol); //Matrix operator=(const Matrix & rhs); // Compiler generate this automatically Matrix operator+(const Matrix & rhs) const; Matrix operator-(const Matrix & rhs) const; Matrix operator*(const Matrix & rhs) const; Matrix & operator+=(const Matrix & rhs); Matrix & operator-=(const Matrix & rhs); Matrix & operator*=(const Matrix & rhs); T& operator()(uint64_t unRow, uint64_t unCol); const T& operator()(uint64_t unRow, uint64_t unCol) const; static Matrix Transpose (const Matrix & matrix); static Matrix Multiply (const Matrix & LeftMatrix, const Matrix & RightMatrix); static Matrix Add (const Matrix & LeftMatrix, const Matrix & RightMatrix); static Matrix Subtract (const Matrix & LeftMatrix, const Matrix & RightMatrix); static Matrix Negate (const Matrix & matrix); // TO DO: static bool IsNull(const Matrix & matrix); static bool IsSquare(const Matrix & matrix); static bool IsFullRowRank(const Matrix & matrix); static bool IsFullColRank(const Matrix & matrix); // TO DO: static uint64_t GetRowRank(const Matrix & matrix); static uint64_t GetColRank(const Matrix & matrix); protected: std::vector<T> TheMatrix; uint64_t m_unRowSize; uint64_t m_unColSize; bool DoesElementExist(uint64_t unRow, uint64_t unCol); };

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• How can I implement an abstract singleton class in Java?

  - by Simon

  Here is my sample abstract singleton class: public abstract class A { protected static A instance; public static A getInstance() { return instance; } //...rest of my abstract methods... } And here is the concrete implementation: public class B extends A { private B() { } static { instance = new B(); } //...implementations of my abstract methods... } Unfortunately I can't get the static code in class B to execute, so the instance variable never gets set. I have tried this: Class c = B.class; A.getInstance() - returns null; and this ClassLoader.getSystemClassLoader().loadClass("B"); A.getInstance() - return null; Running both these in the eclipse debugger the static code never gets executed. The only way I could find to get the static code executed is to change the accessibility on B's constructor to public, and to call it. I'm using sun-java6-jre on Ubuntu 32bit to run these tests.

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• C++ visibility of privately inherited typedefs to nested classes

  - by beldaz

  First time on StackOverflow, so please be tolerant. In the following example (apologies for the length) I have tried to isolate some unexpected behaviour I've encountered when using nested classes within a class that privately inherits from another. I've often seen statements to the effect that there is nothing special about a nested class compared to an unnested class, but in this example one can see that a nested class (at least according to GCC 4.4) can see the public typedefs of a class that is privately inherited by the closing class. I appreciate that typdefs are not the same as member data, but I found this behaviour surprising, and I imagine many others would, too. So my question is threefold: Is this standard behaviour? (a decent explanation of why would be very helpful) Can one expect it to work on most modern compilers (i.e., how portable is it)? #include <iostream> class Base { typedef int priv_t; priv_t priv; public: typedef int pub_t; pub_t pub; Base() : priv(0), pub(1) {} }; class PubDerived : public Base { public: // Not allowed since Base::priv is private // void foo() {std::cout << priv << "\n";} class Nested { // Not allowed since Nested has no access to PubDerived member data // void foo() {std::cout << pub << "\n";} // Not allowed since typedef Base::priv_t is private // void bar() {priv_t x=0; std::cout << x << "\n";} }; }; class PrivDerived : private Base { public: // Allowed since Base::pub is public void foo() {std::cout << pub << "\n";} class Nested { public: // Works (gcc 4.4 - see below) void fred() {pub_t x=0; std::cout << x << "\n";} }; }; int main() { // Not allowed since typedef Base::priv_t private // std::cout << PubDerived::priv_t(0) << "\n"; // Allowed since typedef Base::pub_t is inaccessible std::cout << PubDerived::pub_t(0) << "\n"; // Prints 0 // Not allowed since typedef Base::pub_t is inaccessible //std::cout << PrivDerived::pub_t(0) << "\n"; // Works (gcc 4.4) PrivDerived::Nested o; o.fred(); // Prints 0 return 0; }

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• Derived class linker - is this wrong?

  - by bobobobo

  We have this situation: A B ^ ^ | / C so class A { } class B { } class C : public A, public B { } Now, B wants to access a property in C. How do you do this? The solution I came up with is to place a pointer in B to an instance of C, which is only active (not null) if this B is in fact a C.

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• IEnumerable.GetEnumerator() and IEnumerable<T>.GetEnumerator()

  - by Dylan Lin

  Hi, In the .net framework, there's a generic IEnumerable<T> interface which inherits from the not-generic IEnumerable, and they both have a GetEnumerator() method. The only differents between these two GetEnumerator() is the return type. Now I have a similar design, but when I compile the code, the compiler said: MyInterface<T>.GetItem()' hides inherited member 'MyInterface.GetItem()'. Use the new keyword if hiding was intended. The MyInterface<T>.GetItem() returns a concrete type T, while MyInterface.GetItem() returns type System.Object. So I think if the BCL team guys compile the .net framework, they will get the same warning. I think having compiler warnings is not good, what do you think? And how can I solve this problem? I mean I want to get the concrete type T when calling the MyInterface<T>.GetItem() not just a instance of type System.Object. Thanks in advance! :-)

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• Inheritence in C# question - is overriding internal methods possible?

  - by Jeff Dahmer

  Is it possible to override an internal method's behavior? using System; class TestClass { public string Name { get { return this.ProtectedMethod(); } } protected string ProtectedMethod() { return InternalMethod(); } string InternalMethod() { return "TestClass::InternalMethod()"; } } class OverrideClassProgram : TestClass { // try to override the internal method using new? (compiler warning) new string InternalMethod() { return "OverrideClassProgram::InternalMethod()"; } static int Main(string[] args) { // TestClass::InternalMethod() Console.WriteLine(new TestClass().Name); // TestClass::InternalMethod() ?? are we just screwed? Console.WriteLine(new OverrideClassProgram().Name); return (int)Console.ReadKey().Key; } }

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• Using nested Master Pages

  - by abatishchev

  Hi. I'm very new to ASP.NET, help me please understand MasterPages conception more. I have Site.master with common header data (css, meta, etc), center form (blank) and footer (copyright info, contact us link, etc). <%@ Master Language="C#" AutoEventWireup="true" CodeFile="Site.master.cs" Inherits="_SiteMaster" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head id="tagHead" runat="server"> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <link rel="stylesheet" href="styles.css" type="text/css" /> </head> <body> <form id="frmMaster" runat="server"> <div> <asp:ContentPlaceHolder ID="holderForm" runat="server"></asp:ContentPlaceHolder> <asp:ContentPlaceHolder ID="holderFooter" runat="server">Some footer here</asp:ContentPlaceHolder> </div> </form> </body> </html> and I want to use second master page for a project into sub directory, which would contains SQL query on Page_Load for logging (it isn't necessary for whole site). <%@ Master Language="C#" AutoEventWireup="true" CodeFile="Project.master.cs" Inherits="_ProjectMaster" MasterPageFile="~/Site.master" %> <asp:Content ContentPlaceHolderID="holderForm" runat="server"> <asp:ContentPlaceHolder ID="holderForm" runat="server" EnableViewState="true"></asp:ContentPlaceHolder> </asp:Content> <asp:Content ContentPlaceHolderID="holderFooter" runat="server"> <asp:ContentPlaceHolder ID="holderFooter" runat="server" EnableViewState="true"></asp:ContentPlaceHolder> </asp:Content> But I have a problem: footer isn't displayed. Where is my mistake? Am I right to use second master page as super class for logging? Project page looks like this: <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" MasterPageFile="~/Project.master" %> <asp:Content ContentPlaceHolderID="holderForm" runat="server"> <p>Hello World!</p> </asp:Content> <asp:Content ContentPlaceHolderID="holderFooter" runat="Server"> Some footer content </asp:Content>

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• Persist subclass as superclass using Hibernate

  - by franziga

  I have a subclass and a superclass. However, only the fields of the superclass are needed to be persist. session.saveOrUpdate((Superclass) subclass); If I do the above, I will get the following exception. org.hibernate.MappingException: Unknown entity: test.Superclass at org.hibernate.impl.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:628) at org.hibernate.impl.SessionImpl.getEntityPersister(SessionImpl.java:1366) at org.hibernate.engine.ForeignKeys.isTransient(ForeignKeys.java:203) at org.hibernate.event.def.AbstractSaveEventListener.getEntityState(AbstractSaveEventListener.java:535) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:103) at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93) at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:535) at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:527) at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:523) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:342) at $Proxy54.saveOrUpdate(Unknown Source) How can I persist a subclass as a superclass? I do not prefer creating a superclass instance and then passing the values from the subclass instance. Because, it is easy to forget updating the logic if extra fields are added to superclass in the future.

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• How to Access a descendant object's internal method in C#

  - by Giovanni Galbo

  I'm trying to access a method that is marked as internal in the parent class (in its own assembly) in an object that inherits from the same parent. Let me explain what I'm trying to do... I want to create Service classes that return IEnumberable with an underlying List to non-Service classes (e.g. the UI) and optionally return an IEnumerable with an underlying IQueryable to other services. I wrote some sample code to demonstrate what I'm trying to accomplish, shown below. The example is not real life, so please remember that when commenting. All services would inherit from something like this (only relevant code shown): public class ServiceBase<T> { protected readonly ObjectContext _context; protected string _setName = String.Empty; public ServiceBase(ObjectContext context) { _context = context; } public IEnumerable<T> GetAll() { return GetAll(false); } //These are not the correct access modifiers.. I want something //that is accessible to children classes AND between descendant classes internal protected IEnumerable<T> GetAll(bool returnQueryable) { var query = _context.CreateQuery<T>(GetSetName()); if(returnQueryable) { return query; } else { return query.ToList(); } } private string GetSetName() { //Some code... return _setName; } } Inherited services would look like this: public class EmployeeService : ServiceBase<Employees> { public EmployeeService(ObjectContext context) : base(context) { } } public class DepartmentService : ServiceBase<Departments> { private readonly EmployeeService _employeeService; public DepartmentService(ObjectContext context, EmployeeService employeeService) : base(context) { _employeeService = employeeService; } public IList<Departments> DoSomethingWithEmployees(string lastName) { //won't work because method with this signature is not visible to this class var emps = _employeeService.GetAll(true); //more code... } } Because the parent class lives is reusable, it would live in a different assembly than the child services. With GetAll(bool returnQueryable) being marked internal, the children would not be able to see each other's GetAll(bool) method, just the public GetAll() method. I know that I can add a new internal GetAll method to each service (or perhaps an intermediary parent class within the same assembly) so that each child service within the assembly can see each other's method; but it seems unnecessary since the functionality is already available in the parent class. For example: internal IEnumerable<Employees> GetAll(bool returnIQueryable) { return base.GetAll(returnIQueryable); } Essentially what I want is for services to be able to access other service methods as IQueryable so that they can further refine the uncommitted results, while everyone else gets plain old lists. Any ideas? EDIT You know what, I had some fun playing a little code golf with this... but ultimately I wouldn't be able to use this scheme anyway because I pass interfaces around, not classes. So in my example GetAll(bool returnIQueryable) would not be in the interface, meaning I'd have to do casting, which goes against what I'm trying to accomplish. I'm not sure if I had a brain fart or if I was just too excited trying to get something that I thought was neat to work. Either way, thanks for the responses.

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• Java generics parameters with base of the generic parameter

  - by Iulian Serbanoiu

  Hello, I am wondering if there's an elegant solution for doing this in Java (besides the obvious one - of declaring a different/explicit function. Here is the code: private static HashMap<String, Integer> nameStringIndexMap = new HashMap<String, Integer>(); private static HashMap<Buffer, Integer> nameBufferIndexMap = new HashMap<Buffer, Integer>(); // and a function private static String newName(Object object, HashMap<Object, Integer> nameIndexMap){ .... } The problem is that I cannot pass nameStringIndexMap or nameBufferIndexMap parameters to the function. I don't have an idea about a more elegant solution beside doing another function which explicitly wants a HashMap<String, Integer> or HashMap<Buffer, Integer> parameter. My question is: Can this be made in a more elegant solution/using generics or something similar? Thank you, Iulian

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• Jackson object mapping - map incoming JSON field to protected property in base class

  - by Pete

  We use Jersey/Jackson for our REST application. Incoming JSON strings get mapped to the @Entity objects in the backend by Jackson to be persisted. The problem arises from the base class that we use for all entities. It has a protected id property, which we want to exchange via REST as well so that when we send an object that has dependencies, hibernate will automatically fetch these dependencies by their ids. Howevery, Jackson does not access the setter, even if we override it in the subclass to be public. We also tried using @JsonSetter but to no avail. Probably Jackson just looks at the base class and sees ID is not accessible so it skips setting it... @MappedSuperclass public abstract class AbstractPersistable<PK extends Serializable> implements Persistable<PK> { @Id @GeneratedValue(strategy = GenerationType.AUTO) private PK id; public PK getId() { return id; } protected void setId(final PK id) { this.id = id; } Subclasses: public class A extends AbstractPersistable<Long> { private String name; } public class B extends AbstractPersistable<Long> { private A a; private int value; // getter, setter // make base class setter accessible @Override @JsonSetter("id") public void setId(Long id) { super.setId(id); } } Now if there are some As in our database and we want to create a new B via the REST resource: @POST @Consumes(MediaType.APPLICATION_JSON) @Produces(MediaType.APPLICATION_JSON) @Transactional public Response create(B b) { if (b.getA().getId() == null) cry(); } with a JSON String like this {"a":{"id":"1","name":"foo"},"value":"123"}. The incoming B will have the A reference but without an ID. Is there any way to tell Jackson to either ignore the base class setter or tell it to use the subclass setter instead? I've just found out about @JsonTypeInfo but I'm not sure this is what I need or how to use it. Thanks for any help!

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• Sub-classing templated class without implementing pure virtual method

  - by LeopardSkinPillBoxHat

  I have the following class definition: template<typename QueueItemT> class QueueBC { protected: QueueBC() {}; virtual ~QueueBC() {}; private: virtual IItemBuf* constructItem(const QueueItemT& item) = 0; } I created the following sub-class: class MyQueue : public QueueBC<MyItemT> { public: MyQueue(); virtual ~MyQueue(); }; This compiles fine under VS2005, yet I haven't implemented constructItem() in the MyQueue class. Any idea why?

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• Using LINQ to SQL with multiple databases

  - by Stuart Ferguson

  I am working on a new project and hoping to use LINQ to SQL for the data access but have come across the following issue. I need to have my application access 3 databases with similar but not the same table structure, for example Database1 and Database 2 has a table called tblCustomer with 2 columns CustomerKey and CustomerName Database2 has a table called tblCustomer with 3 columns CustomerKey, CustomerName and CustomerPostCode I am looking for a solution that will allow me a query all three databases without the need for 3 GetCustomerList functions as Database1 and Database2 could use the same function as are the same structure, with an override function for database 3 to bring back the additional field. Is there a way i can declare a base datacontext class to handle Database 1 and 2 with an inherited version for Database 3. Thanks In Advance Stuart Ferguson

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• Inherited varibles are not reading correctly when using bitwise comparisons

  - by Shawn B

  Hey, I have a few classes set up for a game, with XMapObject as the base, and XEntity, XEnviron, and XItem inheriting it. MapObjects have a number of flags, one of them being MAPOBJECT_SOLID. My problem is, that XEntity is the only class that correctly detects MAPOBJECT_SOLID. Both Items are Environs are always considered solid by the game, regardless of the flag's state. What is important, is that Environs and Item should almost never be solid. Here are the relevent code samples: XMapObject: class XMapObject : public XObject { public: Uint8 MapObjectType,Location[2],MapObjectFlags; XMapObject *NextMapObject,*PrevMapObject; XMapObject(); void CreateMapObject(Uint8 MapObjectType); void SpawnMapObject(Uint8 MapObjectLocation[2]); void RemoveMapObject(); void DeleteMapObject(); void MapObjectSetLocation(Uint8 Y,Uint8 X); void MapObjectMapLink(); void MapObjectMapUnlink(); }; XEntity: class XEntity : public XMapObject { public: Uint8 Health,EntityFlags; float Speed,Time; XEntity *NextEntity,*PrevEntity; XItem *IventoryList; XEntity(); void CreateEntity(Uint8 EntityType,Uint8 EntityLocation[2]); void DeleteEntity(); void EntityLink(); void EntityUnlink(); Uint8 MoveEntity(Uint8 YOffset,Uint8 XOffset); }; XEnviron: class XEnviron : public XMapObject { public: Uint8 Effect,TimeOut; void CreateEnviron(Uint8 Type,Uint8 Y,Uint8 X,Uint8 TimeOut); }; XItem: class XItem : public XMapObject { public: void CreateItem(Uint8 Type,Uint8 Y,Uint8 X); }; And lastly, the entity move code. Only entities are capable of moving themselves. Uint8 XEntity::MoveEntity(Uint8 YOffset,Uint8 XOffset) { Uint8 NewY = Location[0] + YOffset, NewX = Location[1] + XOffset; if((NewY >= 0 && NewY < MAPY) && (NewX >= 0 && NewX < MAPX)) { XTile *Tile = GetTile(NewY,NewX); if(Tile->MapList != NULL) { XMapObject *MapObject = Tile->MapList; while(MapObject != NULL) { if(MapObject->MapObjectFlags & MAPOBJECT_SOLID) { printf("solid\n"); return 0; } MapObject = MapObject->NextMapObject; } } if(Tile->Flags & TILE_SOLID && EntityFlags & ENTITY_CLIPPING) { return 0; } this->MapObjectSetLocation(NewY,NewX); return 1; } return 0; } What is wierd, is that the bitwise operator always returns true when the MapObject is an Environ or an Item, but it works correctly for Entities. For debug I am using the printf "Solid", and also a printf containing the value of the flag for both Environs and Items. Any help is greatly appreciated, as this is a major bug for the small game I am working on.

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• How to Access a decendant object's internal method in C#

  - by Giovanni Galbo

  I'm trying to access a method that is marked as internal in the parent class (in its own assembly) in an object that inherits from the same parent. Let me explain what I'm trying to do... I want to create Service classes that return IEnumberable with an underlying List to non-Service classes (e.g. the UI) and optionally return an IEnumerable with an underlying IQueryable to other services. I wrote some sample code to demonstrate what I'm trying to accomplish, shown below. The example is not real life, so please remember that when commenting. All services would inherit from something like this (only relevant code shown): public class ServiceBase<T> { protected readonly ObjectContext _context; protected string _setName = String.Empty; public ServiceBase(ObjectContext context) { _context = context; } public IEnumerable<T> GetAll() { return GetAll(false); } //These are not the correct access modifiers.. I want something //that is accessible to children classes AND between descendant classes internal protected IEnumerable<T> GetAll(bool returnQueryable) { var query = _context.CreateQuery<T>(GetSetName()); if(returnQueryable) { return query; } else { return query.ToList(); } } private string GetSetName() { //Some code... return _setName; } } Inherited services would look like this: public class EmployeeService : ServiceBase<Employees> { public EmployeeService(ObjectContext context) : base(context) { } } public class DepartmentService : ServiceBase<Departments> { private readonly EmployeeService _employeeService; public DepartmentService(ObjectContext context, EmployeeService employeeService) : base(context) { _employeeService = employeeService; } public IList<Departments> DoSomethingWithEmployees(string lastName) { //won't work because method with this signature is not visible to this class var emps = _employeeService.GetAll(true); //more code... } } Because the parent class lives is reusable, it would live in a different assembly than the child services. With GetAll(bool returnQueryable) being marked internal, the children would not be able to see each other's GetAll(bool) method, just the public GetAll() method. I know that I can add a new internal GetAll method to each service (or perhaps an intermediary parent class within the same assembly) so that each child service within the assembly can see each other's method; but it seems unnecessary since the functionality is already available in the parent class. For example: internal IEnumerable<Employees> GetAll(bool returnIQueryable) { return base.GetAll(returnIQueryable); } Essentially what I want is for services to be able to access other service methods as IQueryable so that they can further refine the uncommitted results, while everyone else gets plain old lists. Any ideas?

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• Checking to see if a generic class is inherited from an interface

  - by SnOrfus

  I've got a class that inherits from an interface. That interface defines an event that I'd like to subscribe to in the calling code. I've tried a couple of things, but they all resolve to false (where I know it's true). How can I check to see if a class implements a specific interface. Here's what I've tried (note, the object in question is a usercontrol that implements MyInterface, stored in an array of controls, only some of which implement MyInterface - it is not null): if (this.controls[index].GetType().IsSubclassOf(typeof(MyInterface))) ((MyInterface)this.controls[index]).Event += this.Handler; if (this.controls[index].GetType().IsAssignableFrom(typeof(MyInterface))) ((MyInterface)this.controls[index]).Event += this.Handler; if (this.controls[index].GetType() == typeof(MyInterface)) ((MyInterface)this.controls[index]).Event += this.Handler; All to no avail.

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• How do I override a parent class's functions in python?

  - by wrongusername

  I have a private method def __pickSide(self): in a parent class that I would like to override in the child class. However, the child class still calls the inherited def __pickSide(self):. How can I override the function? The child class's function name is exactly the same as the parent's function name.

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• How to change default image of derived ToolStripButton?

  - by Special Touch

  It seems like a simple task. Create a C# class that derives from ToolStripButton. The derived ToolStripButton should behave exactly the same as the parent class in the designer and the application, except that the default image should be different. Surprisingly just changing the constructor is not sufficient: public CustomToolStripButton() { base.Image = (Image) new Bitmap(typeof(CustomToolStripButton), "CustomImage.bmp"); } When the ToolStripButton is displayed in the designer, the original default image is shown. There must be a simple solution. What could it be?

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