: base(…) If you omit the call to a base constructor it will call the default base constructor automatically. It is mandatory to call a base constructor explicitly if there is no default constructor. Even if there is a default constructor you may still wish to call a different constructor than the default constructor. In … Read more
When a class is (intended as) an abstract class, a protected constructor is exactly right. In that situation you don’t want objects to be instantiated from the class but only use it to inherit from. There are other uses cases, like when a certain set of construction parameters should be limited to derived classes.
Classes have a “class body” that is a constructor. If you use an internal constructor() function, that function would be the same class body as well, and would be what is called when the class is called, hence a class is always a constructor. Constructors requires the use of the new operator to create a … Read more
I don’t think GetMethod will do it, no – but GetConstructor will. using System; using System.Reflection; class Addition { public Addition(int a) { Console.WriteLine(“Constructor called, a={0}”, a); } } class Test { static void Main() { Type type = typeof(Addition); ConstructorInfo ctor = type.GetConstructor(new[] { typeof(int) }); object instance = ctor.Invoke(new object[] { 10 }); … Read more
Design decisions made regarding the way Windows Forms works more or less preclude parameterized .ctors for windows forms components. You can use them, but when you do you’re stepping outside the generally approved mechanisms. Rather, Windows Forms prefers initialization of values via properties. This is a valid design technique, if not widely used. This has … Read more
You can explicitly call constructors and assignment operators: class Base { //… public: Base(const Base&) { /*…*/ } Base& operator=(const Base&) { /*…*/ } }; class Derived : public Base { int additional_; public: Derived(const Derived& d) : Base(d) // dispatch to base copy constructor , additional_(d.additional_) { } Derived& operator=(const Derived& d) { Base::operator=(d); … Read more
Probably the best way to handle this is with a factory function, which calls a private constructor. In Dart, private methods start with an underscore, and “additional” constructors require a name in the form ClassName.constructorName, since Dart doesn’t support function overloading. This means that private constructors require a name, which starts with an underscore (MyComponent._create … Read more
You can specify how to initialize members in the member initializer list: BigMommaClass { BigMommaClass(int, int); private: ThingOne thingOne; ThingTwo thingTwo; }; BigMommaClass::BigMommaClass(int numba1, int numba2) : thingOne(numba1 + numba2), thingTwo(numba1, numba2) {}
Sounds like you’d be better served by a singleton rather than a bunch of static methods class Singleton { /** * * @var Singleton */ private static $instance; private function __construct() { // Your “heavy” initialization stuff here } public static function getInstance() { if ( is_null( self::$instance ) ) { self::$instance = new self(); … Read more
In the first case (ArrayList::new) you are using the constructor which takes an initial capacity argument, in the second case you are not. A large initial capacity (index in your code) causes a large Object[] to be allocated, resulting in your OutOfMemoryErrors. Here are the two constructors’ current implementations: public ArrayList(int initialCapacity) { if (initialCapacity … Read more