Short version extends means: The new class is a child. It gets benefits coming with inheritance. It has all the properties and methods of its parent. It can override some of these and implement new ones, but the parent stuff is already included. implements means: The new class can be treated as the same “shape”, … Read more
// How to extend Validator interface adding isArray() method?? You cannot do this in a file that is a module (some guidance here) and your file is a module because you have import expressValidator. Instead create a extendedValidator.d.ts and add the new stuff for TypeScript’s engine: declare module ExpressValidator { export interface Validator { isArray: … Read more
Yes there are differences which may or may not be relevant in your scenario. Perhaps the most significant is the difference in how members with the same property key are handled when present in both types. Consider: interface NumberToStringConverter { convert: (value: number) => string; } interface BidirectionalStringNumberConverter extends NumberToStringConverter { convert: (value: string) => … Read more
I wouldn’t bother trying to merge your Constants class with this class. It isn’t worth the effort. Just create a new class that does what is necessary for ACRA. Like this: public class MyApplication extends Application { @Override public void onCreate() { super.onCreate(); // do the ACRA init here } } Now you need to … Read more
Yes, you can do it. An interface can extend multiple interfaces, as shown here: interface Maininterface extends inter1, inter2, inter3 { // methods } A single class can also implement multiple interfaces. What if two interfaces have a method defining the same name and signature? There is a tricky point: interface A { void test(); … Read more
There is a little known feature in TypeScript that allows you to use Mixins to create re-usable small objects. You can compose these into larger objects using multiple inheritance (multiple inheritance is not allowed for classes, but it is allowed for mixins – which are like interfaces with an associated implenentation). More information on TypeScript … Read more
List<Dog> is a subtype of List<? extends Animal>, but not a subtype of List<Animal>. Why is List<Dog> not a subtype of List<Animal>? Consider the following example: void mySub(List<Animal> myList) { myList.add(new Cat()); } If you were allowed to pass a List<Dog> to this function, you would get a run-time error. EDIT: Now, if we use … Read more
As of TS3.4 there is no partial type parameter inference. Either you let the compiler try to infer all the type parameters, or you specify all the type parameters. (Well, there are default type parameters but that doesn’t give you what you want: you want to infer the type parameters you leave out, not assign … Read more
What exactly are you trying to achieve? Having two different activities with a common ui, except for some variables or parts of the layout? In this case, I suggest having a base abstract activity, and two concrete inherited subclasses. You define all the common behaviour in the base activity, and have abstract methods for the … Read more
You want to ‘inherit’ from Person’s prototype object: var Person = function (name) { this.name = name; this.type=”human”; }; Person.prototype.info = function () { console.log(“Name:”, this.name, “Type:”, this.type); }; var Robot = function (name) { Person.apply(this, arguments); this.type=”robot”; }; Robot.prototype = Person.prototype; // Set prototype to Person’s Robot.prototype.constructor = Robot; // Set constructor back to … Read more