constructor

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 last year . I've this code snippet: class You{ public You(String s){} } public static void main(String[] args) throws NoSuchMethodException { Constructor[] constructors = You.class.getConstructors(); for(Constructor constructor: constructors){ Class[] parameterTypes = constructor.getParameterTypes(); for(Class c:

问题 what is the meaning of the following sequence diagram and exactly the constructor(that is represented as a create object)? 回答1: It means that ClassA instantiates ClassB . The arrow represents that the constructor of ClassB is called by ClassA 回答2: The message's name "Class B()" is wrong : it should be "create". Is that what confusing you ? 回答3: Chriss, hopefully you've figured it out by now. Please accept Cratylus's answer as it is correct. Here is an example in Java: Main.java package com

问题 I have countless Python classes from various projects from SQLAlchemy (and a couple from Pygame as well), and I recently noticed a pattern in many of them: their constructors always went something like this: class Foo(Base): def __init__(self, first, last, email, mi=""): self.first = first self.last = last self.email = email self.mi = mi ... whereby the only thing the constructor did was to transfer a set of positional arguments into an exactly identically named set of data members,

问题 I have two classes: poly and Node. I create a linked list of Nodes, then I want to create a new poly object that contains a pointer to my first Node object. Here is the calling code: poly *polyObj = new poly(head); I have tested my code and confirmed that "head" contains the linked list of nodes, also head is declared as a Node *. Here are the class definitions: class poly { private: Node *start; public: poly(Node *head) { start = head; } }; class Node { private: double coeff; int exponent;

问题 I'd like to be able to initialize a derived class from a base class, like so: class X { public: X() : m(3) {} int m; }; class Y : public X { public: Y() {} Y(const & X a) : X(a) {} }; Is there anything dangerous or unusual by doing that? I want it because I'm deserializing a bunch of objects who's type I don't immediately know, so I basically want to use X just as some temp storage while I'm reading the whole serialized file, and then create my Y objects (and W, X, Y objs, depending on the

问题 A implicit default constructor has an empty body and an empty initializer list (primitive types undefined, and the default constructor is called for user defined types). This post says MyClass *c = new MyClass(); does indeed do a member-wise value-initialization, but what is the point of calling the default constructor when doing MyClass c; ? Is the implicit default constructor called, to ensure that the default constructors for user defined types (which might have non-trivial default

问题 I want to modify a constructor to use an initialization list as in the following example: class Foo { public: Foo(std::wstring bar); private: std::wstring bar; }; // VERSION 1: Foo::Foo(std::wstring bar) {this->bar = bar} // VERSION 2: Foo::Foo(std::wstring bar) : this->bar(bar) {} // ERROR! Unfortunately I can't do version 2 because you can't use the this pointer for data members since (I'm guessing) they don't exist yet at that point. How then, do I deal with the name hiding issue (i.e. my

问题 here's the default AccountController.cs that's generated by the framework. public class AccountController : Controller { public IFormsAuthentication FormsAuth { get; private set; } public IMembershipService MembershipService { get; private set; } public AccountController() : this(null, null) { } public AccountController(IFormsAuthentication formsAuth, IMembershipService membershipService) { FormsAuth = formsAuth ?? new FormsAuthenticationService(); MembershipService = membershipService ?? new

问题 I have data type data Constants = Constants { x1 :: Int, x2 :: Int, ... , x100 :: Int } Names x1, x2, ..., x100 may have irregular naming. Is there an elegant way to create Constants object from list of 100 Int values? mkConstants :: [Int] -> Constants mkConstants [x1, x2, ..., x100] = Constants x1 x2 ... x100 -- The bad way What about reverse task? extractInts :: Constants -> [Int] extractInts (Constants x1 x2 ... x100) = [x1, x2, ..., x100] -- The bad way 回答1: Edit: see Reading long data

问题 I have a parent class with 2 constructor and the derived class trying to call the constructor of parent in 2 different methods public class Parent { public Parent() { //some stuffs } public Parent(string st) { //some stuffs } } Now I have a derived class with two methods. I Have to use Parent -constructor in one method and the Parent(string st) in other method. But here It is always calling the Parent -constructor. Below is the derived class public class Derived : Parent { public void GetData