default-constructor

问题 This question already has answers here : Java default constructor (11 answers) Closed 8 months ago . I am a newbie in java and was wondering "Why default constructor is not provided by compiler when class contains parametrized constructor defined by user?" 回答1: When an author decides to not provide any constructor, it is perfectly fine that the compiler adds that default constructor. Obviously the user doesn't care "how" objects of that class are created, he accepts that the "default" kicks

问题 A "Singular Iterator" is defined as an: iterators that are not associated with any sequence. A null pointer, as well as a default-constructed pointer (holding an indeterminate value) is singular My question 1 would be: Is a default constructed iterator considered a "Singular Iterator"? Secondly, I have been told here that: Results of most expressions are undefined for singular values; the only exceptions are destroying an iterator that holds a singular value, the assignment of a non-singular

问题 I have the following class: class Tileset { //base class public: static std::vector<Tileset*> list; virtual ~Tileset() = 0; protected: std::vector<Tile> tiles_list; sf::Texture sheet; private: //non copiable Tileset(const Tileset&); Tileset& operator=(const Tileset&); }; where sf::Texture has a default constructor From my understanding a default constructor should be generated since every member can be default-constructed too. Yet I have a compiler error when I try to construct a derived

问题 It's possible that someone has already asked about this but googling for "default", "defaulted", "explicit" and so on doesn't give good results. But anyway. I already know there are some differences between an explicitly defined default construtor (i.e. without arguments) and an explicitly defined defaulted constructor (i.e. with the keyword default ), from here: The new keyword =default in C++11 But what are the differences between an explicitly defined defaulted constructor and implicitly

问题 It's possible that someone has already asked about this but googling for "default", "defaulted", "explicit" and so on doesn't give good results. But anyway. I already know there are some differences between an explicitly defined default construtor (i.e. without arguments) and an explicitly defined defaulted constructor (i.e. with the keyword default ), from here: The new keyword =default in C++11 But what are the differences between an explicitly defined defaulted constructor and implicitly

问题 I am trying to understand how default constructor (provided by the compiler if you do not write one) versus your own default constructor works. So for example I wrote this simple class: class A { private: int x; public: A() { std::cout << "Default constructor called for A\n"; } A(int x) { std::cout << "Argument constructor called for A\n"; this->x = x; } }; int main (int argc, char const *argv[]) { A m; A p(0); A n(); return 0; } The output is : Default constructor called for A Argument

问题 I am trying to understand how default constructor (provided by the compiler if you do not write one) versus your own default constructor works. So for example I wrote this simple class: class A { private: int x; public: A() { std::cout << "Default constructor called for A\n"; } A(int x) { std::cout << "Argument constructor called for A\n"; this->x = x; } }; int main (int argc, char const *argv[]) { A m; A p(0); A n(); return 0; } The output is : Default constructor called for A Argument

问题 Below is the class used as the value in a map: class Book { int m_nId; public: // Book() { } <----- Why is this required? Book( int id ): m_nId( id ) { } }; Inside main(): map< int, Book > mapBooks; for( int i = 0; i &lt 10; ++i ) { Book b( i ); mapBooks[ i ] = b; } The statement causing the error is: mapBooks[ i ] = b; If I add a default constructor, the error does not appear. However, I don't understand why the need. Can anyone explain? If I use insert() , the problem does not appear. By

问题 If I define a class with a private default constructor and a public constructor that has parameters, how can I access the private constructor? public class Bob { public String Surname { get; set; } private Bob() { } public Bob(string surname) { Surname = surname; } } I can access the private constructor via a static method on the class like this: public static Bob GetBob() { return new Bob(); } I thought that I could access the private constructor via an extension method, since (according to

问题 This question already has answers here : Conditions for automatic generation of default/copy/move ctor and copy/move assignment operator? (3 answers) Closed 6 years ago . This is supposed to be a trivial question but I could not find it explicitly on stackoverflow. The following will be defined implicitly if not provided by the user. default (parameterless) constructor copy constructor copy assignment operator destructor But I have read somewhere (which I cant seem to find now), that there