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• edmx - The operation could not be completed - After adding Inheritance

  - by vdh_ant

  Hey guys I have an edmx model which I have draged 2 tables onto - One called 'File' and the other 'ApplicaitonFile'. These two tables have a 1 to 1 relationship in the database. If I stop here everything works fine. But in my model, I want 'ApplicaitonFile' to inherit from 'File'. So I delete the 1 to 1 relationship then configure 'ApplicaitonFile' from 'File' and then remove the FileId from 'ApplicaitonFile' which was the primary key. (Note I am following the instructions from here). If I leave the model open at this point everything is fine, but as soon as I close it, if I try and reopen it again I get the following error "The operation could not be completed". I have been searching for a solution and found this - http://stackoverflow.com/questions/944050/entity-model-does-not-load but as far as I can tell I don't have a duplicate InheritanceConnectors (although I don't know exactly what I'm looking for but I can't see anything out of the ordinary - like 2 connectors with the same name) and the relationship I originally have is a 1 to 1 not a 1 to 0..1 Any ideas???

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• Is currying just a way to avoid inheritance?

  - by Alex Mcp

  So my understanding of currying (based on SO questions) is that it lets you partially set parameters of a function and return a "truncated" function as a result. If you have a big hairy function takes 10 parameters and looks like function (location, type, gender, jumpShot%, SSN, vegetarian, salary) { //weird stuff } and you want a "subset" function that will let you deal with presets for all but the jumpShot%, shouldn't you just break out a class that inherits from the original function? I suppose what I'm looking for is a use case for this pattern. Thanks!

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• @webservice inheritance java

  - by javamonkey79

  I am trying to build a java ee webservice that has a common base class, but the child classes are the actual @webservice classes (and expose the parent class methods as @webmethod's) Like this: public abstract class Parent { @WebMethod public void doSomething(){//...does stuff} } @WebService public class Child extends Parent {} I've tried (and have failed): - annotating the parent class as a webservice as well - making sure all parent methods are annotated with @WebMethod Is this possible, if so, how?

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• Inheritance of Custom Attributes on Abstract Properties

  - by Marty Trenouth

  I've got a custom attribute that I want to apply to my base abstract class so that I can skip elements that don't need to be viewed by the user when displaying the item in HTML. It seems that the properties overriding the base class are not inheriting the attributes. Does overriding base properties (abstract or virtual) blow away attributes placed on the original property? From Attribute class Defination [AttributeUsage(AttributeTargets.Property, Inherited = true, AllowMultiple = false)] public class NoHtmlOutput : Attribute { } From Abstract Class Defination [NoHtmlOutput] public abstract Guid UniqueID { get; set; } From Concrete Class Defination public override Guid UniqueID{ get{ return MasterId;} set{MasterId = value;}} From class checking for attribute Type t = o.GetType(); foreach (PropertyInfo pi in t.GetProperties()) { if (pi.GetCustomAttributes(typeof(NoHtmlOutput), true).Length == 1) continue; // processing logic goes here }

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• ValueError with multi-table inheritance in Django Admin

  - by jorde

  I created two new classes which inherit model Entry: class Entry(models.Model): LANGUAGE_CHOICES = settings.LANGUAGES language = models.CharField(max_length=2, verbose_name=_('Comment language'), choices=LANGUAGE_CHOICES) user = models.ForeignKey(User) country = models.ForeignKey(Country, null=True, blank=True) created = models.DateTimeField(auto_now=True) class Comment(Entry): comment = models.CharField(max_length=2000, blank=True, verbose_name=_('Comment in English')) class Discount(Entry): discount = models.CharField(max_length=2000, blank=True, verbose_name=_('Comment in English')) coupon = models.CharField(max_length=2000, blank=True, verbose_name=_('Coupon code if needed')) After adding these new models to admin via admin.site.register I'm getting ValueError when trying to create a comment or a discount via admin. Adding entries works fine. Error msg: ValueError at /admin/reviews/discount/add/ Cannot assign "''": "Discount.discount" must be a "Discount" instance. Request Method: GET Request URL: http://127.0.0.1:8000/admin/reviews/discount/add/ Exception Type: ValueError Exception Value: Cannot assign "''": "Discount.discount" must be a "Discount" instance. Exception Location: /Library/Python/2.6/site-packages/django/db/models/fields/related.py in set, line 211 Python Executable: /usr/bin/python Python Version: 2.6.1

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• PowerShell Cmdlet Parameters and Inheritance

  - by Adam Driscoll

  I have an interface: public interface X {} I have a class: public class Y : X {} I have one cmdlet: [Cmdlet("Get", "Y")] public class GetYCmdlet : PSCmdlet { protected override void ProcessRecord() { WriteObject(new Y()); } } I have another cmdlet: [Cmdlet("Set", "X")] public class SetYCmdlet : PSCmdlet { [Parameter] public X SomeObj {get;set;} } When I do this: $y = Get-Y Set-X -SomeObj $y I get this: Could not convert "Y" to "X". Method not supported. Any ideas?

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• Expression Tree with Property Inheritance causes an argument exception

  - by Adam Driscoll

  Following this post: link text I'm trying to create an expression tree that references the property of a property. My code looks like this: public interface IFoo { void X {get;set;} } public interface IBar : IFoo { void Y {get;set;} } public interface IFooBarContainer { IBar Bar {get;set;} } public class Filterer { //Where T = "IFooBarContainer" public IQueryable<T> Filter<T>(IEnumerable<T> collection) { var argument = Expression.Parameter(typeof (T), "item"); //... //where propertyName = "IBar.X"; PropertyOfProperty(argument, propertyName); } private static MemberExpression PropertyOfProperty(Expression expr, string propertyName) { return propertyName.Split('.').Aggregate<string, MemberExpression>(null, (current, property) => Expression.Property(current ?? expr, property)); } } I receive the exception: System.ArgumentException: Instance property 'X' is not defined for type 'IBar' ReSharper turned the code in the link above into the condensed statement in my example. Both forms of the method returned the same error. If I reference IBar.Y the method does not fail.

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• Using implicit conversion as a substitute for multiple inheritance in .NET

  - by Daniel Plaisted

  I have a situation where I would like to have objects of a certain type be able to be used as two different types. If one of the "base" types was an interface this wouldn't be an issue, but in my case it is preferable that they both be concrete types. I am considering adding copies of the methods and properties of one of the base types to the derived type, and adding an implicit conversion from the derived type to that base type. Then users will be able treat the derived type as the base type by using the duplicated methods directly, by assigning it to a variable of the base type, or by passing it to a method that takes the base type. It seems like this solution will fit my needs well, but am I missing anything? Is there a situation where this won't work, or where it is likely to add confusion instead of simplicity when using the API?

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• metaclass multiple inheritance inconsistency

  - by Matt Anderson

  Why is this: class MyType(type): def __init__(cls, name, bases, attrs): print 'created', cls class MyMixin: __metaclass__ = MyType class MyList(list, MyMixin): pass okay, and works as expected: created <class '__main__.MyMixin'> created <class '__main__.MyList'> But this: class MyType(type): def __init__(cls, name, bases, attrs): print 'created', cls class MyMixin: __metaclass__ = MyType class MyObject(object, MyMixin): pass Is not okay, and blows up thusly?: created <class '__main__.MyMixin'> Traceback (most recent call last): File "/tmp/junk.py", line 11, in <module> class MyObject(object, MyMixin): pass TypeError: Error when calling the metaclass bases Cannot create a consistent method resolution order (MRO) for bases object, MyMixin

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• Problems with inheritance query view and one to many association in entity framework 4

  - by Kazys

  Hi, I have situation in with I stucked and don't know way out. The problem is in my bigger model, but I have made small example which shows the same problem. I have 4 tables. I called them SuperParent, NamedParent, TypedParent and ParentType. NamedParent and TypedParent derives from superParent. TypedParent has one to many association with ParentType. I describe mapping for entities using queryView. The problem is then I want to get TypedParents and Include ParentType I get the following exception: An error occurred while preparing the command definition. See the inner exception for details. --- System.ArgumentException: The ResultType of the specified expression is not compatible with the required type. The expression ResultType is 'Transient.reference[PasibandymaiModel.SuperParent]' but the required type is 'Transient.reference[PasibandymaiModel.TypedParent]'. Parameter name: arguments[1] To get TypedParents I use following code: context.SuperParent.OfType().Include("ParentType"); my edmx file: <edmx:Edmx Version="2.0" xmlns:edmx="http://schemas.microsoft.com/ado/2008/10/edmx"> <!-- EF Runtime content --> <edmx:Runtime> <!-- SSDL content --> <edmx:StorageModels> <Schema Namespace="PasibandymaiModel.Store" Alias="Self" Provider="System.Data.SqlClient" ProviderManifestToken="2005" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns="http://schemas.microsoft.com/ado/2009/02/edm/ssdl"> <EntityContainer Name="PasibandymaiModelStoreContainer"> <EntitySet Name="NamedParent" EntityType="PasibandymaiModel.Store.NamedParent" store:Type="Tables" Schema="dbo" /> <EntitySet Name="ParentType" EntityType="PasibandymaiModel.Store.ParentType" store:Type="Tables" Schema="dbo" /> <EntitySet Name="SuperParent" EntityType="PasibandymaiModel.Store.SuperParent" store:Type="Tables" Schema="dbo" /> <EntitySet Name="TypedParent" EntityType="PasibandymaiModel.Store.TypedParent" store:Type="Tables" Schema="dbo" /> <AssociationSet Name="fk_NamedParent_SuperParent" Association="PasibandymaiModel.Store.fk_NamedParent_SuperParent"> <End Role="SuperParent" EntitySet="SuperParent" /> <End Role="NamedParent" EntitySet="NamedParent" /> </AssociationSet> <AssociationSet Name="fk_TypedParent_ParentType" Association="PasibandymaiModel.Store.fk_TypedParent_ParentType"> <End Role="ParentType" EntitySet="ParentType" /> <End Role="TypedParent" EntitySet="TypedParent" /> </AssociationSet> <AssociationSet Name="fk_TypedParent_SuperParent" Association="PasibandymaiModel.Store.fk_TypedParent_SuperParent"> <End Role="SuperParent" EntitySet="SuperParent" /> <End Role="TypedParent" EntitySet="TypedParent" /> </AssociationSet> </EntityContainer> <EntityType Name="NamedParent"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Name="ParentId" Type="int" Nullable="false" /> <Property Name="Name" Type="nvarchar" Nullable="false" MaxLength="100" /> </EntityType> <EntityType Name="ParentType"> <Key> <PropertyRef Name="ParentTypeId" /> </Key> <Property Name="ParentTypeId" Type="int" Nullable="false" StoreGeneratedPattern="Identity" /> <Property Name="Name" Type="nvarchar" MaxLength="100" /> </EntityType> <EntityType Name="SuperParent"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Name="ParentId" Type="int" Nullable="false" StoreGeneratedPattern="Identity" /> <Property Name="SomeAttribute" Type="nvarchar" Nullable="false" MaxLength="100" /> </EntityType> <EntityType Name="TypedParent"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Name="ParentId" Type="int" Nullable="false" /> <Property Name="ParentTypeId" Type="int" Nullable="false"/> </EntityType> <Association Name="fk_NamedParent_SuperParent"> <End Role="SuperParent" Type="PasibandymaiModel.Store.SuperParent" Multiplicity="1" /> <End Role="NamedParent" Type="PasibandymaiModel.Store.NamedParent" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="SuperParent"> <PropertyRef Name="ParentId" /> </Principal> <Dependent Role="NamedParent"> <PropertyRef Name="ParentId" /> </Dependent> </ReferentialConstraint> </Association> <Association Name="fk_TypedParent_ParentType"> <End Role="ParentType" Type="PasibandymaiModel.Store.ParentType" Multiplicity="1" /> <End Role="TypedParent" Type="PasibandymaiModel.Store.TypedParent" Multiplicity="*" /> <ReferentialConstraint> <Principal Role="ParentType"> <PropertyRef Name="ParentTypeId" /> </Principal> <Dependent Role="TypedParent"> <PropertyRef Name="ParentTypeId" /> </Dependent> </ReferentialConstraint> </Association> <Association Name="fk_TypedParent_SuperParent"> <End Role="SuperParent" Type="PasibandymaiModel.Store.SuperParent" Multiplicity="1" /> <End Role="TypedParent" Type="PasibandymaiModel.Store.TypedParent" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="SuperParent"> <PropertyRef Name="ParentId" /> </Principal> <Dependent Role="TypedParent"> <PropertyRef Name="ParentId" /> </Dependent> </ReferentialConstraint> </Association> <Function Name="ChildDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ChildId" Type="int" Mode="In" /> </Function> <Function Name="ChildInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="Name" Type="nvarchar" Mode="In" /> <Parameter Name="ParentId" Type="int" Mode="In" /> </Function> <Function Name="ChildUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ChildId" Type="int" Mode="In" /> <Parameter Name="ParentId" Type="int" Mode="In" /> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="NamedParentDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> </Function> <Function Name="NamedParentInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="Name" Type="nvarchar" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> </Function> <Function Name="NamedParentUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="ParentTypeDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> </Function> <Function Name="ParentTypeInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="ParentTypeUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="TypedParentDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> </Function> <Function Name="TypedParentInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> </Function> <Function Name="TypedParentUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> </Function> </Schema> </edmx:StorageModels> <!-- CSDL content --> <edmx:ConceptualModels> <Schema Namespace="PasibandymaiModel" Alias="Self" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns="http://schemas.microsoft.com/ado/2008/09/edm"> <EntityContainer Name="PasibandymaiEntities" annotation:LazyLoadingEnabled="true"> <EntitySet Name="ParentType" EntityType="PasibandymaiModel.ParentType" /> <EntitySet Name="SuperParent" EntityType="PasibandymaiModel.SuperParent" /> <AssociationSet Name="ParentTypeTypedParent" Association="PasibandymaiModel.ParentTypeTypedParent"> <End Role="ParentType" EntitySet="ParentType" /> <End Role="TypedParent" EntitySet="SuperParent" /> </AssociationSet> </EntityContainer> <EntityType Name="NamedParent" BaseType="PasibandymaiModel.SuperParent"> <Property Type="String" Name="Name" Nullable="false" MaxLength="100" FixedLength="false" Unicode="true" /> </EntityType> <EntityType Name="ParentType"> <Key> <PropertyRef Name="ParentTypeId" /> </Key> <Property Type="Int32" Name="ParentTypeId" Nullable="false" annotation:StoreGeneratedPattern="Identity" /> <Property Type="String" Name="Name" MaxLength="100" FixedLength="false" Unicode="true" /> <NavigationProperty Name="TypedParent" Relationship="PasibandymaiModel.ParentTypeTypedParent" FromRole="ParentType" ToRole="TypedParent" /> </EntityType> <EntityType Name="SuperParent" Abstract="true"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Type="Int32" Name="ParentId" Nullable="false" annotation:StoreGeneratedPattern="Identity" /> <Property Type="String" Name="SomeAttribute" Nullable="false" MaxLength="100" FixedLength="false" Unicode="true" /> </EntityType> <EntityType Name="TypedParent" BaseType="PasibandymaiModel.SuperParent"> <NavigationProperty Name="ParentType" Relationship="PasibandymaiModel.ParentTypeTypedParent" FromRole="TypedParent" ToRole="ParentType" /> <Property Type="Int32" Name="ParentTypeId" Nullable="false" /> </EntityType> <Association Name="ParentTypeTypedParent"> <End Type="PasibandymaiModel.ParentType" Role="ParentType" Multiplicity="1" /> <End Type="PasibandymaiModel.TypedParent" Role="TypedParent" Multiplicity="*" /> <ReferentialConstraint> <Principal Role="ParentType"> <PropertyRef Name="ParentTypeId" /> </Principal> <Dependent Role="TypedParent"> <PropertyRef Name="ParentTypeId" /> </Dependent> </ReferentialConstraint> </Association> </Schema> </edmx:ConceptualModels> <!-- C-S mapping content --> <edmx:Mappings> <Mapping Space="C-S" xmlns="http://schemas.microsoft.com/ado/2008/09/mapping/cs"> <EntityContainerMapping StorageEntityContainer="PasibandymaiModelStoreContainer" CdmEntityContainer="PasibandymaiEntities"> <EntitySetMapping Name="ParentType"> <QueryView> SELECT VALUE PasibandymaiModel.ParentType(tp.ParentTypeId, tp.Name) FROM PasibandymaiModelStoreContainer.ParentType AS tp </QueryView> </EntitySetMapping> <EntitySetMapping Name="SuperParent"> <QueryView> SELECT VALUE CASE WHEN (np.ParentId IS NOT NULL) THEN PasibandymaiModel.NamedParent(sp.ParentId, sp.SomeAttribute, np.Name) WHEN (tp.ParentId IS NOT NULL) THEN PasibandymaiModel.TypedParent(sp.ParentId, sp.SomeAttribute, tp.ParentTypeId) END FROM PasibandymaiModelStoreContainer.SuperParent AS sp LEFT JOIN PasibandymaiModelStoreContainer.NamedParent AS np ON sp.ParentId = np.ParentId LEFT JOIN PasibandymaiModelStoreContainer.TypedParent AS tp ON sp.ParentId = tp.ParentId </QueryView> <QueryView TypeName="PasibandymaiModel.TypedParent"> SELECT VALUE PasibandymaiModel.TypedParent(sp.ParentId, sp.SomeAttribute, tp.ParentTypeId) FROM PasibandymaiModelStoreContainer.SuperParent AS sp INNER JOIN PasibandymaiModelStoreContainer.TypedParent AS tp ON sp.ParentId = tp.ParentId </QueryView> <QueryView TypeName="PasibandymaiModel.NamedParent"> SELECT VALUE PasibandymaiModel.NamedParent(sp.ParentId, sp.SomeAttribute, np.Name) FROM PasibandymaiModelStoreContainer.SuperParent AS sp INNER JOIN PasibandymaiModelStoreContainer.NamedParent AS np ON sp.ParentId = np.ParentId </QueryView> </EntitySetMapping> </EntityContainerMapping> </Mapping> </edmx:Mappings> </edmx:Runtime> </edmx:Edmx> I have tried using AssociationSetMapping instead of using Association with ReferentialConstraint. But then couldn't insert related entities at once, becouse entity framework didn't provided entity key of inserted entities for related entities. Thanks for any idea

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• Add function to built-in class using inheritance

  - by Steven

  I'm trying to add a IsImage property that I wrote myself to the HttpPostedFile class, so that if a user is uploading a file, I can do something like this: FileUpload1.PostedFile.IsImage How can I do that in C#?

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• base enum class inheritance

  - by Sasha

  Is there a pattern where I can inherit enum from another enum in C++?? something like that: enum eBase { one=1, two, three }; enum eDerived: public Base { four=4, five, six };

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• has_many inheritance

  - by dweebsonduty

  I have a model called company that has_many users then users belongs_to company. If something belongs to users will it also belong to company?

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• Inheritance: when implementing an interface which define a base class property why cant the class im

  - by Deepak

  Lets create some interfaces public interface ITimeEventHandler { string Open(); } public interface IJobTimeEventHandler: ITimeEventHandler { string DeleteJob(); } public interface IActivityTimeEventHandler: ITimeEventHandler { string DeleteActivity(); } public interface ITimeEvent { ITimeEventHandler Handler; } Another Interface public interface IJobTimeEvent :ITimeEvent { int JobID; } Create a class public class JobTimeEvent : IJobTimeEvent { public int JobID = 0; public IJobTimeEventHandler Handler = null; } My question is .. when implementing an interface which define a base class property why cant the class implementing interface return a derived class type object ?? For ex in class JobTimeEvent, IJobtimeEvent needs a property of type ITimeEventHandler but why IJobTimeEventHandler type is not allowed which derived from ITimeEventHandler

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• pointer-to-pointer of derived class in multiple inheritance

  - by Abdul jalil

  i have 3 classes A,B and C. C is derived from A and B. i get pointer to pointer of class C and cast to A** , and B ** , the variable that hold the the B** has the address of A** in my example B ** BdoublePtr hold the address of A** .i am using the following code #include "conio.h" #include "stdio.h" #include "string.h" class A{ public: A() { strA=new char[30]; strcpy(strA,"class A"); } char *strA; }; class B { public: B() { strB=new char[30]; strcpy(strB,"class B"); } char *strB; }; class C :public A, public B { public: C() { strC=new char[30]; strcpy(strC,"class C"); } char *strC; }; int main(void) { C* ptrC=new C(); A * Aptr=(A*)ptrC; printf("\n class A value : %s",Aptr-strA); B * Bptr=(B*)ptrC; printf("\n class B value :%s",Bptr-strB); printf("\n\nnow with double pointer "); A ** AdoublePtr=(A **)&ptrC; Aptr=AdoublePtr; printf("\n class A value : %s",Aptr-strA); B * BdoublePtr=(B **)&ptrC; Bptr=*BdoublePtr; printf("\n class B value : %s",Bptr-strB); getch(); return 0; }

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• Public property List needs to Concat 2 types with inheritance

  - by Bernard

  I have 2 lists: one of type A and one of type Aa. type Aa is inherited from type A. So: List<A> listA = new List<A>(); List<Aa> listAa = new List<Aa>(); with class Aa : A I have: public property Lists<A> { get { List<A> newList = new List<A>(); //return concat of both lists foreach(List l in listA) { newList.Add(l); } foreach(List l in listAa) { newList.Add(l); } } Can I somehow use Concat instead of the foreach loop? i.e. get { return listA.Concat(listAa); } // this doesn't work And secondly, how do I do the set part of the property? set { //figure out the type of variable value and put into appropriate list? }

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• actionscript-3: refactor interface inheritance to get rid of ambiguous reference error

  - by maxmc

  hi! imagine there are two interfaces arranged via composite pattern, one of them has a dispose method among other methods: interface IComponent extends ILeaf { ... function dispose() : void; } interface ILeaf { ... } some implementations have some more things in common (say an id) so there are two more interfaces: interface ICommonLeaf extends ILeaf { function get id() : String; } interface ICommonComponent extends ICommonLeaf, IComponent { } so far so good. but there is another interface which also has a dispose method: interface ISomething { ... function dispose() : void; } and ISomething is inherited by ICommonLeaf: interface ICommonLeaf extends ILeaf, ISomething { function get id() : String; } As soon as the dispose method is invoked on an instance which implements the ICommonComponent interface, the compiler fails with an ambiguous reference error because ISomething has a method called dispose and ILeaf also has a dispose method, both living in different interfaces (IComponent, ISomething) within the inheritace tree of ICommonComponent. I wonder how to deal with the situation if the IComponent, the ILeaf and the ISomething can't change. the composite structure must also work for for the ICommonLeaf & ICommonComponent implementations and the ICommonLeaf & ICommonComponent must conform to the ISomething type. this might be an actionscript-3 specific issue. i haven't tested how other languages (for instance java) handle stuff like this.

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• drawing to a JPanel without inheritance

  - by g.rocket

  Right now I'm working on a program that throws up a bunch of separate (generated at runtime) images, each in their own window. To do this i've tried this approach: public void display(){ JFrame window = new JFrame("NetPart"); JPanel canvas = new JPanel(); window.getContentPane().add(canvas); Graphics g = canvas.getGraphics(); Dimension d = getSize(); System.out.println(d); draw(g,new Point(d.minX*50,d.maxY*50), 50); window.setSize(d.size(50)); window.setResizable(false); window.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE); window.setVisible(true); } public void draw(Graphics g, Point startLoc, int scale){ // generate and draw the image } public Dimension getSize(){ //returns my own dimensions class } However, this throws a NullPointerException in draw, claiming that the graphics is null. is there any way to externally draw to a JPanel from outside it (not inherit from JPanel and override PaintComponent)? Any help would be appreciated.

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• singleton inheritance question

  - by maxxtack

  how do i (and does it makes any sense?) inherit from the singleton class other classes that need the same functionality?

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• cake php AppController and inheritance

  - by RSK

  hello folks........ In many tutorial of Acl component in cakephp i got instruction that add component either in AppController or in all the other controllers which inherits AppController....... but problem is var $components=array('Auth',Acl); when i use the above line in AppConroller i cant use the Auth or Acl component... but when i use the same code in all the child classes it works fine........ what will be the problem thanks in advance any help will be appreciated.

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• Inheritance issue with ivar on the iPhone

  - by Buffalo

  I am using the BLIP/MYNetwork library to establish a basic tcp socket connection between the iPhone and my computer. So far, the code builds and runs correctly in simulator but deploying to device yields the following error: error: property 'delegate' attempting to use ivar '_delegate' declared in super class of 'TCPConnection' @interface TCPConnection : TCPEndpoint { @private TCPListener *_server; IPAddress *_address; BOOL _isIncoming, _checkedPeerCert; TCPConnectionStatus _status; TCPReader *_reader; TCPWriter *_writer; NSError *_error; NSTimeInterval _openTimeout; } /** The delegate object that will be called when the connection opens, closes or receives messages. */ @property (assign) id<TCPConnectionDelegate> delegate; /** The delegate messages sent by TCPConnection. All methods are optional. */ @protocol TCPConnectionDelegate <NSObject> @optional /** Called after the connection successfully opens. */ - (void) connectionDidOpen: (TCPConnection*)connection; /** Called after the connection fails to open due to an error. */ - (void) connection: (TCPConnection*)connection failedToOpen: (NSError*)error; /** Called when the identity of the peer is known, if using an SSL connection and the SSL settings say to check the peer's certificate. This happens, if at all, after the -connectionDidOpen: call. */ - (BOOL) connection: (TCPConnection*)connection authorizeSSLPeer: (SecCertificateRef)peerCert; /** Called after the connection closes. You can check the connection's error property to see if it was normal or abnormal. */ - (void) connectionDidClose: (TCPConnection*)connection; @end @interface TCPEndpoint : NSObject { NSMutableDictionary *_sslProperties; id _delegate; } - (void) tellDelegate: (SEL)selector withObject: (id)param; @end Does anyone know how I would fix this? Would I simply declare _delegate as a public property of the base class "TCPEndPoint"? Thanks for the help ya'll!

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• Ruby class instance variables and inheritance

  - by rlandster

  I have a Ruby class called LibraryItem. I want to associate with every instance of this class an array of attributes. This array is long and looks something like ['title', 'authors', 'location', ...] Note that these attributes are not really supposed to be methods, just a list of attributes that a LibraryItem has. Next, I want to make a subclass of LibraryItem called LibraryBook that has an array of attributes that includes all the attributes of LibraryItem but will also include many more. Eventually I will want several subclasses of LibraryItem each with their own version of the array @attributes but each adding on to LibraryItem's @attributes (e.g., LibraryBook, LibraryDVD, LibraryMap, etc.). So, here is my attempt: class LibraryItem < Object class << self; attr_accessor :attributes; end @attributes = ['title', 'authors', 'location',] end class LibraryBook < LibraryItem @attributes.push('ISBN', 'pages'] end This does not work. I get the error undefined method `push' for nil:NilClass

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• abstract method signature, inheritance, and "Do" naming convention

  - by T. Webster

  I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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• OO - inheritance vs. decoration problem

  - by Karel J

  Hi all, I have an OOP-related question. I have an interface, say: class MyInterface { public int getValue(); } In my project, this interface is implemented by 7 implementations: class MyImplementation1 implements MyInterface { ... } ... class MyImplementation7 implements MyInterface { ... } These implementations are used by several different modules. For some modules, the behaviour of the MyInterface must be adjusted slightly. Let's that it must return the value of the implementator + 1 (for the sake of example). I solved this by creating a little decorator: class MyDifferentInterface implements MyInterface { private MyInterface i; public MyDifferentInterface(MyInterface i) { this.i = i; } public int getValue() { return i.getValue() + 1; } } This does the job. Here is my problem: one of the modules doesn't accept an MyInterface parameter, but MyImplementation4 directly. The reason for this is that this module needs specific behaviour of MyImplementation4, which are not covered by the interface MyInterface on itself. But, and here comes the difficulty, this module must also work on the modified version of MyImplementation4. That is, getValue() must return +1; What is the best way to solve this? I fail to come up with a solution which does not include lots of code duplicates. Please note that although the example above is pretty small and simple, the interface and the decorator is quite large and complicated. Thanks a lot all.

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• Inheritance domain classes in Grails

  - by Tomáš

  Hi gurus how can I get Collection of specific Class? I use inheriance: On Planet live Human. Humans are dividing to Men and Women. class Planet{ String name static hasMany = [ humans : Human ] } class Human{ String name static belongsTo = [Planet] } class Man extends Human{ int countOfCar } class Woman extends Human{ int coutOfChildren } now a neet to get only Collection of Man or Collection of Woman: get all humans on planet is simple all = Planet.get(1).humans but what can I get only woman or men? womenLivedOnMars = Planet.get(1).getOnlyWoman menLivedOnJupiter = Planet.get(2).getOnlyMan Thanks for your help Tom

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