constructor

问题 This question already has answers here : Closed 11 years ago . Possible Duplicate: C# constructor execution order class Foo { public int abc; Foo() { abc = 3; } } class Bar : Foo { Bar() : base() { abc = 2; } } In the example above, when an object of Bar is created, what will be the value of BarObject.abc? Is the base constructor called first, or is Bar() run, /then/ the base() constructor? 回答1: It'll be 2. Constructors run in order from base class first to inherited class last. Note that

问题 I have a pretty simple and straightforward question. What is the standardized way, or the right way, of calling another constructor of a class, along with the base constructor of such class? I understand that the second example does not work. It just seems hackish to be doing it the third way. So what is the way that the people who designed C# expected users to do this? For example: public class Person { private int _id; private string _name; public Person() { _id = 0; } public Person(string

问题 //listen for messages channel.on("messageAdded", function (message) { //render new message console.log("New awesome message", message) //this is null for some reason console.log("Stringify 3",JSON.stringify(message.state.aggregatedDeliveryReceipt)) } But by storing it as a global object via console right click, I am able to do a console.log(temp1.state.aggregatedDeliveryReceipt) and get back The problem is that, when I use the same state.aggregatedDeliveryReceipt on my JS file, I am unable to

问题 //listen for messages channel.on("messageAdded", function (message) { //render new message console.log("New awesome message", message) //this is null for some reason console.log("Stringify 3",JSON.stringify(message.state.aggregatedDeliveryReceipt)) } But by storing it as a global object via console right click, I am able to do a console.log(temp1.state.aggregatedDeliveryReceipt) and get back The problem is that, when I use the same state.aggregatedDeliveryReceipt on my JS file, I am unable to

问题 This question already has answers here : What is array to pointer decay? (9 answers) Closed 2 years ago . I came across a piece of C++ code in one of my projects that initializes a vector with two inputs. One of the inputs is an existing array, and the other is the same array plus the array length. I found a similar piece of code on another site: // Create an array of string objects std::string arr[] = {"first", "sec", "third", "fourth"}; // Initialize vector with a string array std::vector

问题 I know this question has already been ask, but I couldn't figure it out. I have two classes Point and Line, and 2 Points are members of Line. However in the Line constructor I get "no default constructor exists for the class" error. How can I fix this problem? #include <cstdlib> #include <cmath> #include "PointClass.h" using namespace std; class Line { public: Line(const Point& p1, const Point& p2) { this->point1 = p1; this->point2 = p2; } Point point1; Point point2; static double Distance

问题 I am new to C++ programming language, i have a confusion about order of calling the constructor in inheritance. my question is even though the constructor and destructor are not inherited by derived class why the base class constructor will call when i create a derived class object. 回答1: The purpose of a constructor is to define how the data members should be initialised. Since a derived class inherits the data members from the base class, any constructor of the derived class must define not

问题 is there any way I can declare constructor to take HashSet as one of arguments and then pass HashSet value directly as argument during object initialization? I mean something like this: public class Order { private Set<Product> products = new HashSet<Product>(); public Order (???) { this.products = ??? } } and then, while initializing object: Order order = new Order("product1", "product2", "product3"); is it possible? 回答1: You can use varargs : public class Order { private Set<Product>

问题 is there any way I can declare constructor to take HashSet as one of arguments and then pass HashSet value directly as argument during object initialization? I mean something like this: public class Order { private Set<Product> products = new HashSet<Product>(); public Order (???) { this.products = ??? } } and then, while initializing object: Order order = new Order("product1", "product2", "product3"); is it possible? 回答1: You can use varargs : public class Order { private Set<Product>

问题 import java.util.ArrayList; import java.util.Random; public class College { // instance variables - replace the example below with your own private ArrayList<Student> students; public College() { // initialise instance variables ArrayList<Student> students = new ArrayList<Student>(); students.add("Student 1"); students.add("Student 2"); students.add("Student 3"); } } basically it highlights the .add showing the error message "java.lang.IllegalArgumentException: bound must be positive", I don