extends

I have a parent service which has some dependencies like @Injectable() export class ParentService{ constructor(private http:Http, private customService:CustomService){} } and I want to extend the service @Injectable() export class ChildService extends ParentService{ constructor (){ super(??) <= typescript now asking to enter two parameters according to ParentServie's constructor } } Edit----------------- @Injectable() export class ParentService{ constructor(private http:Http, private customService:CustomService){} get(){this.http.get(...)} } @Injectable() export class ChildService extends

Why must implement always be written after extend in a class declaration? For example: public class Register extends ActionSupport implements ModelDriven Why can it not be: public class Register implements ModelDriven extends ActionSupport The latter produces a compile-time error. When the Java compiler turns a class into bytecode, it must first look to a parent class. That is because the underlying implementation of classes is to point to the bytecode of the parent class - which holds the relevant methods and fields. Then it adds in pointers to the code of the child class functions - some of

I would like to know what man and child have in common and how they differ. class Person { name: string; age: number; } class child extends Person {} class man implements Person {} Radim Köhler Short version extends means: The new class is a child . It gets benefits coming with inheritance. It has all properties, methods as its parent. It can override some of these and implement new, but the parent stuff is already included. implements means: The new class can be treated as the same "shape" , while it is not a child . It could be passed to any method where the Person is required, regardless of

The following statements: URLClassLoader ucl = (URLClassLoader) ClassLoader.getSystemClassLoader(); Class<URLClassLoader> uclc = ucl.getClass(); fail with error: Type mismatch: cannot convert from Class<capture#2-of ? extends URLClassLoader> to Class<URLClassLoader> Why do I need a cast, here? I found several posts explaining why You can't do the reverse (assign T to a ), but that's (kind of) obvious and understood. NOTE: I am coding this under eclipse Luna, so I don't know if it's a Luna Quirk or if there's something I really dont understand in generics. Covariance vs contravariance vs

In java, to make a function that returns an object that is the same type as a parameter and extends a certain class, I would type: public <T extends MyClass> T foo(T bar) {...} Is there a C++ equivalent of this? In other words, how do I make a function that takes any class that extends a certain class, and returns that same type? (This is for the purpose of abstract/pure virtual classes). AndyG We can use enable_if here if you have C++11 or higher available to you template<typename T, typename std::enable_if<std::is_base_of<MyClass, T>::value>::type* = nullptr> T Foo(T bar) { return T(); } For

This question already has an answer here: Implements vs extends: When to use? What's the difference? 17 answers What's the difference between the following keywords in Java: implements , extends ? blahman An interface is an abstract specification of how a class should behave whilst a class is a concrete implementation of such a specification. Therefore, when you write implements you're saying that you are fulfilling some abstract specification in the implementation you've written. extends means that you take either an implementation ( class ) or specification ( interface ) and add to it with

Suppose I have a pure abstract class (that is, an abstract class without any implementation): abstract class A { abstract m(): void; } Like in C# and Java, I can extend the abstract class: class B extends A { m(): void { } } But unlike in C# and Java, I can also implement the abstract class: class C implements A { m(): void { } } How do classes B and C behave differently? Why would I choose one versus the other? (Currently, the TypeScript handbook and language specification don't cover abstract classes.) The implements keyword treats the A class as an interface, that means C has to implement

In Java, I can do the following: (assume Subclass extends Base ): ArrayList<? extends Base> aList = new ArrayList<Subclass>(); What is the equivalent in C# .NET? There is no ? extends keyword apparently and this does not work: List<Base> aList = new List<Subclass>(); Actually there is an Equivalent(sort of), the where keyword. I don't know how "close" it is. I had a function I needed to do something similar for. I found an msdn page about it. I don't know if you can do this inline for a variable, but for a class you can do: public class MyArray<T> where T: someBaseClass or for a function