generics

问题 I have a generic function with two parameters. The second one is based on the value of first parameter. The code works with just one type variable but when I add another one, cannot call the function. This works perfectly: type Event<T> = T extends 'string' ? string : number; type input = 'string' | 'number'; function test<U extends input>(module: U, event: Event<U>) { //... } //No errors test('number', 2); // Generates error as expected test('string', 2); But when another generic variable is

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I want to use vararg with generics with different types of each arguments what I've already tried: class GeneralSpecification<T> { fun <P> ifNotNullCreateSpec(vararg propToCreateFun: Pair<P?, (P) -> Specification<T>>): List<Specification<T>> = propToCreateFun.mapNotNull { (prop, funCreateSpec) -> prop?.let(funCreateSpec) } ... } but I can't use this like: ifNotNullCreateSpec("asdf" to ::createStringSpec, 5 to ::createIntSpec) (different types in vararg pairs) How can I use vararg with

问题 I want to use vararg with generics with different types of each arguments what I've already tried: class GeneralSpecification<T> { fun <P> ifNotNullCreateSpec(vararg propToCreateFun: Pair<P?, (P) -> Specification<T>>): List<Specification<T>> = propToCreateFun.mapNotNull { (prop, funCreateSpec) -> prop?.let(funCreateSpec) } ... } but I can't use this like: ifNotNullCreateSpec("asdf" to ::createStringSpec, 5 to ::createIntSpec) (different types in vararg pairs) How can I use vararg with

问题 I'm hoping someone can explain this to me as I'm confused about it. I have a series of inheritance amongst my classes and interfaces, with a factory to instantiated the correct object. However, I am getting a Cannot implicitly convert type 'Conn' to IConn. An explicit conversion exists (are you missing a cast?) Here is an trimmed down version of the code. public abstract class Id { public int Id { get; set; } } public abstract class Id_SourceId { public int SourceId { get; set; } } public

问题 If you need to cast a generic type parameter to a specific type we can cast it to a object and do the casting like below, void SomeMethod(T t) { SomeClass obj2 = (SomeClass)(object)t; } Is there a better way to achieve this rather than casting it to a object and then to a specific type. Problem I have a generic function which accepts a generic type parameter, inside the function based on a type checking I do some operations like below void SomeMethod(T t) { if (typeof(T).Equals(typeof(TypeA))

问题 As of Java 8 you can have default or static methods implemented in Interfaces as the below public interface DbValuesEnumIface<ID, T extends Enum<T>> { T fromId(ID id); ID getId(); static String getDescriptionKey(){ return "this is a test"; } } I would like to declare the above with the static method having a signature that uses bounds defined by the implementing classes since the method's implementation should be the same for all,with the only thing different should be the generics declared,

问题 Yesterday, I was explaining C#'s generic constraints to my friends. When demonstrating the where T : CLASSNAME constraint, I whipped up something like this: public class UnusableClass<T> where T : UnusableClass<T> { public static int method(T input){ return 0; } } And was really surprised to see it compile. After a bit of thinking, however, I figured it was perfectly legal from the point of view of the compiler - UnusableClass<T> is as much of a class as any other that can be used in this