constructor

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 implement good design patterns for a program I am writing. I have a class structure like this. abstract class SomeBase { public SomeObject obj { get; protected set; } protected SomeBase(SomeObject x) { obj = x; } //Other methods and fields... } public class SomeDerived : SomeBase { public SomeDerived() : base(new SomeObject(this)) { } } Now as I;m sure you now, you can't pass this in a contructor because the object hasn't bee initialized. But I was really hoping there was a

问题 It is possible to pass uninitialized object to a parent class like in the following example class C { public: C(int i): m_i(i) {}; int m_i; } class T { public: T(C & c): m_c(c) { }; C & m_c; }; class ST : public T { public: ST(): T(m_ci), m_ci(999) { }; C m_ci; }; In class T constructor, c is a reference to uninitialized object. If class T were using c object during construction, this would possibly lead to an error. But since it's not, this compiles and works fine. My question is - does it

问题 Is there a way to construct a vector as the concatenation of 2 vector s (Other than creating a helper function?) For example: const vector<int> first = {13}; const vector<int> second = {42}; const vector<int> concatenation = first + second; I know that vector doesn't have an addition operator like string , but that's the behavior that I want. Such that concatenation would contain: 13 and 42. I know that I can initialize concatenation like this, but it prevents me from making concatenation

问题 This question already has answers here : In this specific case, is there a difference between using a member initializer list and assigning values in a constructor? (12 answers) Closed 6 years ago . I was just going through random pages on Cprogramming.com and noticed the Constructors and Destructors tutorial/example page. They have used the following method of defining a constructor: class String { private: char *str; int size; public: String() : str(NULL), size(0) { } // <- This statement

问题 which declaration/instantiation is better and WHY ? public class MainWindow { private Test _test; public MainWindow() { _test = new Test(); } } OR public class MainWindow { private Test _test = new Test(); public MainWindow() { } } 回答1: Ask yourself this question: what happens when you add other constructors to MainWindow ? Do you want to then have to remember to invoke other constructors to ensure that _test is correctly initialized? Or is it okay for _test to not be initialized if another

问题 Common design practice is to make instance variables private and have public getters and setters to access them. But many times I have seen code samples on the internet that have constructors that assign values directly to the private instance variable instead of using the setters inside constructors. Am I missing something? public class Person{ private String name; public Person(String name){ //is this right, seems like the whole encapsulation purpose is defeated this.name = name; //shouldn

问题 In kotlin, how to make the setter of properties in primary constructor private? class City(val id: String, var name: String, var description: String = "") { fun update(name: String, description: String? = "") { this.name = name this.description = description ?: this.description } } I want the setter of properties name to be private, and the getter of it public, how can I do? 回答1: The solution is to create a property outside of constructor and set setter's visibility. class Sample(var id: Int,

问题 In kotlin, how to make the setter of properties in primary constructor private? class City(val id: String, var name: String, var description: String = "") { fun update(name: String, description: String? = "") { this.name = name this.description = description ?: this.description } } I want the setter of properties name to be private, and the getter of it public, how can I do? 回答1: The solution is to create a property outside of constructor and set setter's visibility. class Sample(var id: Int,