generics

问题 Using Swift 2, in my contrived example I am converting a String to an Int or more specifically an Int or an Int? using a generic. In the case where the Int? should be nil the cast will fail with a fatalError: fatal error: unexpectedly found nil while unwrapping an Optional value These look like they may be similar/duplicate questions: Swift - casting a nil core data string as an optional value Swift: detecting an unexpected nil value in a non-optional at runtime: casting as optional fails My

问题 I have a generic object: MyGenericObject(of T), how do I register a custom renderer in log4net in the config file? For example, if this was a normal object the following would work: <renderer renderingClass="MyObjectRenderer, MyClassLibrary" renderedClass="MyObject, MyClassLibrary" /> However I don't know how to write this for Generics, I attempted this: <renderer renderingClass="MyObjectRenderer, MyClassLibrary" renderedClass="MyObject(Of MyNonGenericObject), MyClassLibrary" /> but this

问题 I am trying to learn Kotlin, and test how it works with spring boot. My application is using a mongo database to store data and I have a Jersey resource for retrieving data. I am testing it using spring-boot-test and RestTestTemplate . The RestTestTemplate has an exchange method which takes a ParameterizedTypeReference . This class has a protected constructor. So the only way I managed to use it from Kotlin was like this: class ListOfPeople : ParameterizedTypeReference<List<Person>>() Here is

问题 I have generic type that looks like: public class GenericClass<T, U> where T : IComparable<T> { // Class definition here } I then have a collection of these instances. What is the cleanest way to pass through the type constraints? public class GenericCollection<V> where V : GenericClass<T, U> // This won't compile { private GenericClass<T, U>[] entries; public V this[index] { get{ return this.entries[index]; } } } Is there perhaps a better way to design this? I think that specifying

问题 Okay, this is tricky. Say I have a list: List<Foo> MyList; Foo is a common abstract class which is used for all components in the system. Some of these component classes are generic: public class Bar<T> : Foo { public void MethodCommonToAllBar() { ... } } And some classes may extend the generic ones: public class Baz : Bar<int> public class Bat : Bar<string> I'd like a way to extract from MyList a set of all objects of type Bar<anything> , so that I may call MethodCommonToAllBar() on each of

问题 Okay, this is tricky. Say I have a list: List<Foo> MyList; Foo is a common abstract class which is used for all components in the system. Some of these component classes are generic: public class Bar<T> : Foo { public void MethodCommonToAllBar() { ... } } And some classes may extend the generic ones: public class Baz : Bar<int> public class Bat : Bar<string> I'd like a way to extract from MyList a set of all objects of type Bar<anything> , so that I may call MethodCommonToAllBar() on each of

问题 I am experiencing some weird behavior when using Generic Types and null operator. Why does obj2.CurrentDate return a date value that appears to be incorrect when using the ? (short hand). If I long hand the null operator (if) in the property then it returns the correct and expected value. I thought the ? was the equivalent to the if(expression, returnIfTrue, returnIfFalse). Also, if the generic type constructor is removed, then the null operator works as expected. Why is this? Return If

问题 I am experiencing some weird behavior when using Generic Types and null operator. Why does obj2.CurrentDate return a date value that appears to be incorrect when using the ? (short hand). If I long hand the null operator (if) in the property then it returns the correct and expected value. I thought the ? was the equivalent to the if(expression, returnIfTrue, returnIfFalse). Also, if the generic type constructor is removed, then the null operator works as expected. Why is this? Return If

问题 I would like to create a generic function. I'm novice in generic. I've 3 private lists of different type. I want a public generic method for return 1 item of the list. I've the code below. (I have it simplifie) TFilter = class private FListFilter : TObjectList<TFilterEntity>; FListFilterDate : TObjectList<TFilterDate>; FListFilterRensParam : TObjectList<TFilterRensParam>; public function yGetFilter<T>(iIndice : integer) : T; .... function TFilter .yGetFilter<T>(iIndice : integer) : T; begin

问题 This is a followup to this question. Essentially, I have the following classes: public class Parent<B> { public B b; public Parent(B b) { this.b = b; } } public class Child<B> extends Parent<B> { public Child(B b) { super(b); } } And I'd like to have another class that references them: public class Foo<ParentType<B> extends Parent<B>, B> { // ^ syntax error here: > expected public ParentType<B> parent; public B otherItem; public Foo(ParentType<B> parent, B otherItem) { this.parent = parent;