subclass

问题 Is there any technical difference between a class which inherits from another class and a class which is a subclass of it? What's the difference between A and B in the following code: A) public class foo { ... private class bar {...} } B) public class foo { ...} private class bar extends foo {...} 回答1: In the inheriting situation, you can treat the derived class like its base class. That is, you can keep a collection of base class references around and call their methods without needing to

问题 I've to get all the instances of a class C and subclasses (direct or indirect) of C, in SPARQL. I can get all the direct subclasses of C in this way: SELECT ?entity WHERE { ?subclass rdfs:subClassOf :C . ?entity rdf:type ?subclass . } But I can't get the instances of an indirect subclass and neither any instance of C. As I know (I've pre-calculated them) all the subclasses (direct and indirect of C), and I can build a dynamic query, is it possible build a query like the following one? SELECT

问题 Let's say I have some classes like this: abstract class View(val writer: XMLStreamWriter) { // Implementation } class TestView(writer: XMLStreamWriter) extends View(writer) { // Implementation } Most subclasses of View are not going to take different constructor arguments. I would like to be able to write something like this: class TestView extends View { // Implementation } Is there some shortcut to write subclasses so that you don't have to explicitly define the constructor args and pass

问题 I have this code segment: if (cell == nil) { CGRect cellFrame = CGRectMake(0,0,300,250); cell = [[UITableViewCell alloc] initWithFrame:cellFrame reuseIdentifier:CellTableIndetifier]; CGRect nameLabelRect = CGRectMake(0, 5, 70, 20); UILabel* nameLabel = [[UILabel alloc] initWithFrame:nameLabelRect]; nameLabel.textAlignment = NSTextAlignmentCenter; nameLabel.text = @"Name"; nameLabel.font = [UIFont boldSystemFontOfSize:12]; [cell.contentView addSubview: nameLabel]; CGRect colorLabelRect =

问题 I am trying to define a default style list object: class ilist(list): def __init__(self,r=list(),dft=None): list.__init__(self,r) self.dft=dft def __getitem__(self,n): if len(self)<=n: for i in range(n-len(self)+1): self.append(self.dft) for i,v in enumerate(self): if i+1==len(self): return v x=ilist() print x[4] print x It works. >>> None [None, None, None, None, None] But I think it's terrible to query my ilist. I've tried the following method: def __getitem__(self,n): from operator import

问题 I have a class called Test and a class called SubTest who extends Text , I would like to have a method in the Test class who will returns the instance of SubTest when called, I would like to do : SubTest test = new SubTest().setTest("Hello!").setOtherTest("Hi!"); The setTest() and setOtherTest() methods should be in the Test class. But when I do : public Test setTest(String test) { return this; } It only returns the instance of Test so I have to cast Test to SubTest , but I don't want to. Is

问题 I'm trying to achieve something like this public abstract class BaseEvent { public abstract void Dispatch(IEventHandler handler); } public class MyEvent : BaseEvent { public override void Dispatch(IMyEventHandler handler) { handler.OnMyEvent(this); } } public interface IEventHandler { } public interface IMyEventHandler : IEventHandler { void OnMyEvent(MyEvent e); } The problem is that the compiler complains saying that MyEvent doesn't implement BaseEvent since Dispatch is taking an

问题 I have a generics class with a subclass that provides specific types. public abstract class GenericBase<T> where T:Interface1 { } I subclass the generics with specific implementations: public class Customer: GenericBase<Type1> ( Type1 implements Interface1 ). I have another abstract base class that has a reference to this: protected GenericBase<Interface1> genericInstance; Finally, when I attempt to assign the genericInstance to an instance of the base class, it gives me a compiler error,

问题 I have a class structure similar to this: public abstract class Device { public int DeviceId { get; set; } //Additional Properties } public class DeviceA : Device { //Specific Behaviour } public class DeviceB : Device { //Specific Behaviour } I need to retrieve a list of Devices, or a single Device which is instantiated as the appropriate derived type (based upon a Type value in the Device Record in the DB). That is, the collection of Device objects should contain a number of objects with

问题 Because of this issue here, I'm trying to write a custom JsonConverter that handles cases where you subclass a list or a collection, then add extra properties to it. As such, one approach would be to ignore all base-class properties and only serialize those in the defined class. (Technically this won't work because if you subclass that subclass you break the serialization, but it did make me wonder...) Is it possible via reflection (well I know the answer is 'yes' because Reflector does