constructor

问题 I've got an issue creating entities in Kotlin. In particular, it's about passing data to a super class. Find an example below. I've got an abstract super class called Trackable that classes can extend. It has a user property that stores who has created that particular object. abstract class Trackable( var createdBy: User ) : Persistable() An class called Contract would now implement the Trackable super class with a compile-time error for the time being: @Entity data class Contract( var

问题 I was wondering how to catch an exception from a constructor in a derived class with C#. Something as such: public class MyClassA { public MyClassA() { //Do the work if (failed) { throw new Exception("My exception"); } } } public class MyClassB : MyClassA { public MyClassB() { //How to catch exception from a constructor in MyClassA? } } 回答1: Do not even try to figure out how to do this. If the base class constructor is throwing an exception, it means the base class is in a bad state. If the

问题 Is it possible to use es6 constructor instructions on another instance by changing the "this" context (call, apply or other)? This is possible using es5 "classes". Here is a small example of what I mean: function ES5() { this.foo = 'foo'; } class ES6 { constructor() { this.bar = 'bar'; } } var a = new ES6(); ES5.call(a); console.log(a.foo + a.bar); //foobar var b = new ES5(); //Reflect.construct(ES6); ?? ES6.call(b); //TypeError: Class constructor ES6 cannot be invoked without 'new' console

问题 I was told the following was possible due to changes in C++11: class SomeType { int number; public: SomeType(int new_number) : number(new_number) {} SomeType() : SomeType(42) {} }; But when I try to build I get an error: "SomeType" is not a nonstatic data member or base class of class "SomeType" error C2614: 'SomeType' : illegal member initialization: 'SomeType' is not a base or member Is this feature not yet supported in Visual Studio 2010? Do I need to configure something to get this to

问题 If I save some object in a php session variable $_SESSION['geoip'] = new GeoIP(); and then on future page loads I use $geoip = $_SESSION['geoip'] , will it call the constructor? My constructor for that GeoIP class is making a call to an remote API (CURL), so I was hoping to save on API calls by only doing it the first time and then storing the results in my session variable. GeoIP.class.php: require_once('geoPlugin.class.php'); class GeoIP { public $currentIP; public $geoplugin; function _

问题 I've read pages and pages about JavaScript prototypal inheritance, but I haven't found anything that addresses using constructors that involve validation. I've managed to get this constructor to work but I know it's not ideal, i.e. it's not taking advantage of prototypal inheritance: function Card(value) { if (!isNumber(value)) { value = Math.floor(Math.random() * 14) + 2; } this.value = value; } var card1 = new Card(); var card2 = new Card(); var card3 = new Card(); This results in three

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 years ago . Im a complete beginner in the Java especially OOP so please pardon my naivety but recently while going through Head First Java,they said, A constructor is a code that runs when somebody says new on a class type. But then i tried this code to see what actually happened but to my surprise the output was totally

问题 I have the following class: public class ArrayObjects<E> implements SomeImp<E>{ int maxCapacity, actualSize; public ArrayObjects(){ maxCapacity = 10; array = (E[]) new Object[maxCapacity]; } } Eclipse marks an error and says the following: "array cannot be resolved to a variable" Also it shows some additional details: -Type safety: Unchecked cast from Object[] to E[] Does anyone know what am I doing wrong? My goal is to have an array in my class constructor that can hold any kind of object

问题 I don't know how to solve the following JavaScript problem: function A() { var numbers = []; this.addNumber = function(number) { numbers.push(number); } this.getNumbers = function() { return numbers; } } A.prototype.alertNumbers = function() { var numbers = this.getNumbers(); var length = numbers.length; var number; var numbersString = ""; for (var i = 0; i < length; i++) { number = numbers[i]; numbersString += " " + number; } alert(numbersString); } B.prototype = new A(); function B() { this

问题 For whatever reason, I cannot find this question anywhere else, nor can I find the answer online. If I have the following: package temp1; public class MainClass { public static void main(String[] args) { } public MainClass(int radius_x, int area_x, int circumference_x) { int radius = radius_x; int area = area_x; int circumference = circumference_x; } } Assuming that this is even correct usage, then how would I actually use the variables defined in the constructor here? They only work inside