Constructors are the same as methods in this respect – if you don’t give an explicit public, private or protected then the constructor gets the default “package private” visibility. It can be called from within the same class or from any other class in the same package, but not from subclasses in a different package … Read more
If you have virtual members that are going to be invoked during construction (against best advice, but we’ve already agreed on that), then you need to move your initialization into a separate method, that can protect itself against multiple calls (i.e. if init has already happened, return immediately). That method will then be invoked by … Read more
You can use class as a type which is the way you’re using it. So, whether Hero is an interface or class it doesn’t matter because you’re using it as a type. class Hero { id: number; name: string } or interface Hero { id: number; name: string } The following doesn’t concern whether Hero … Read more
It’s called exactly to avoid problems. A new object serving as result is initialized from the locally-defined object, then the locally defined object is destroyed. In case of deep-copy user-defined constructor it’s all the same. First storage is allocated for the object that will serve as result, then the copy constructor is called. It uses … Read more
The JPA specification requires that all persistent classes (@Entity) have a no-arg constructor, public or protected. (note that this is not necessarily true when dealing with some implementation like Hibernate, see this answer). This is needed because JPA uses the default constructor method to create a bean class using the reflection API. Indeed if your … Read more
You get that compilation error because the signature of the implementation function does not satisfy the empty constructor you declared. As you want to have the default constructor, it should be: class MyItem { public name: string; public surname: string; public category: string; public address: string; constructor(); constructor(name:string, surname: string, category: string, address?: string); constructor(name?: … Read more
JAXB can support this case using an XML Adapter. Consider you have the following object with no zero-arg constructor: package blog.immutable; public class Customer { private final String name; private final Address address; public Customer(String name, Address address) { this.name = name; this.address = address; } public String getName() { return name; } public Address … Read more
You can create initializer functions that take a pointer to a structure. This was common practice. Also functions that create a struct and initialize it (like a factory) – so there is never a time where the struct is “uninitialized” in the “client” code. Of course – that assumes people follow the convention and use … Read more
The method foo() is private, so you don’t inherit it and can’t call it directly from the C class. However, you can see private methods and constructor from B since everything is declared in the same containing class, and access them with super, which is why super() works. In the same way, you can access … Read more
I believe backwards compatibility plays a big part here. If the user defines any of the “Rule of three” functions (copy ctor, copy assignment op, dtor), it can be assumed the class does some internal resource management. Implicitly defining a move constructor could suddenly make the class invalid when compiled under C++11. Consider this example: … Read more