Advertisements How to make a custom List constructor in Dart? My attempt was to extend a List but it seems to not work. The class ‘FooList’ can’t extend ‘List’ because ‘List’ only has factory constructors (no generative constructors), and ‘FooList’ has at least one generative constructor Here is the context: typedef JsonMap = Map<String, dynamic>;… Read More How to Extend List<T> in Dart?

Advertisements I have one Angular component which has the following input @Input() filterColumnFunction?: FilterColumnFunction; This function type (‘template’) is the following export type FilterColumnFunction = <T>(columnFilters: { [key: string]: string }, items: T[]) => T[]; The given function to the component is filterColumnFunction = (columnFilters: { [key: string]: string }, items: MyDto[]): MyDto[] => {… Read More How to expect a specific Typescript function template as an Angular component input

Advertisements class definition public interface ITest { Long foo(); } public class Test implements ITest{ @Override public Long foo() { return 0L; } } methods public Map<Long, List<? extends ITest>> moo() { List<Test> a = List.of(new Test()); Map<Long, List<? extends ITest>> b = Map.of(1L, a); return b; } public Map<Long, List<? extends ITest>> koo() {… Read More List class wrapped by Map class do not support generic types in JAVA?

Advertisements I am looking for a utility type that will allow me to extract the generic parameter of a set, but I only have available the typed set, so basically type Bar = Set<Foo>; type Baz = SomethingMagic<Bar>; // Baz should equal Foo >Solution : You can do that with the infer keyword: type SomethingMagic<T>… Read More Utility type to extract `Foo` from `type Bar = Set<Foo>` with just `Bar`

Advertisements Given that public final class String implements java.io.Serializable, Comparable<String>, CharSequence, Constable, ConstantDesc { … Why a String return is not valid? >Solution : You misunderstand what this means. You apparently think it means: "T is anything that is a Comparable or some subtype of it". This is incorrect. after all, that concept is represented… Read More Why String can't be returned from a method with return type <T extends Comparable<T>> T?

Advertisements There is a function function createStats<K extends string[]>(arr: K): Stats<K[number]> and when I do this for example const testStats = createStats(["maxHealth"]) testStats is Stats<string> and I want it to be Stats<"maxHealth"> The only way I know how to fix it is to add as const. But I don’t want to write as const through… Read More How to make generics more specific?

Advertisements I have three classes in play here: public class MyClass1<T, ID> { @Getter private static class IdHolder<ID> { private ID id; } } public class MyClass2<T> { public MyClass2(Class<? extends T> type) { } public List<T> fetch() { } } Inside of MyClass1, I need to create an instance of MyClass2 and call the… Read More Java generics TypeReference for collection method not working

Advertisements Processing large amounts of data (gigabytes) I use indexes to data arrays. Since access to data could lead to cache inefficiency, I want to cache some data from array together with the index which gives dramatic speedup for operations through indexes. The amount of cached data is compile-time choice which should include zero amount… Read More What is the approach to handle optional class members?

Advertisements I want to associate function’s generic type to other class inside the function. I get error Generic parameter ‘T’ is not used in function signature for code below. func someFunc<T: Codable>() { let nmyClass = MyClass<T>() } How can I make the error go away without returning T? When I add return T? from… Read More Generic parameter 'T' is not used in function signature

Advertisements There are lots of examples of Kotlin generics but this is one I’ve not come across. I’ve simplified it down to this: open class Fruit class Apple : Fruit() class Orange : Fruit() abstract class Helper<T : Fruit> { open fun save(something: T) {} } class AppleHelper : Helper<Apple>() { override fun save(something: Apple)… Read More Kotlin context sensitive generics