constructor

问题 I've developed a recent interest in (re-)learning programming, so I have taken up C++ as it is a commonly used language. However, I've ran into a roadblock, and I have doubts whether my solution is the best way to go around it. I have a relatively complex class (for me anyways), with around 20 variables, which have been divided into 4 groups for simplification. It also has a parent class which is called during object initialization. However, I do not have a need to set these to values other

问题 I am trying to modify the following fields in a class constructor using javassist : Label Label1 = new Label(new StringBuilder().append(user.name)); Label Label2 = new Label(new StringBuilder().append(user.time.toString()); I want to prepend text to the 2 labels. The text can be accessed and set using getText() and setText(). How could I achieve this? 回答1: The simplest approach is to use the ability to modify the constructor body with java code and let javassist create the bytecode. So you

问题 I wanted to call a class method without creating an object or calling the constructor on the document.ready event. I tried following different options but nothing worked. var objReportsInterface; class ReportsInterface extends ReportBase { constructor() { super(); objReportsInterface = this; } subCategories() {} } $(document).ready(function() { $("dropdown").on('change', function() objReportsInterface.subCategories(); }) }) <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1

问题 ORIGINAL POST When compiled, the following code produces error C2436: '__ctor' : member function or nested class in constructor initializer list in Child.h #include Parent.h class Child : public Parent { public: Child (List* pList) : Parent::Parent(pList) { } }; Here the parent class: in Parent.h class __declspec(dllimport) Parent : public GrandParent { public: Parent (List* pList = NULL); } in Parent.cpp Parent::Parent (List* pList) : m_a(1) ,m_b(1) ,GrandParent(pList) { } Isn't it right the

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: Initializing fields in constructor - initializer list vs constructor body In a lecture I attended, the lecturer talked briefly in C++ about non-default class constructors. He stated specifically that one version was preferable to the other. He showed these two examples: Point::Point(double x, double y, double z) : x_(x), y_(y), z_(z) {} Point::Point(double x, double y, double z) { x_= x; y_= y; z_= z; } He

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: Initializing fields in constructor - initializer list vs constructor body In a lecture I attended, the lecturer talked briefly in C++ about non-default class constructors. He stated specifically that one version was preferable to the other. He showed these two examples: Point::Point(double x, double y, double z) : x_(x), y_(y), z_(z) {} Point::Point(double x, double y, double z) { x_= x; y_= y; z_= z; } He

问题 I'm working on some OpenCV code and developed it in VS 2008 on windows. I'm trying to run the code on Linux with g++ but I get the error "Cannot call constructor 'ImageProcessor::ImageProcessor' directly" for ImageProcessor and all of the other classes I have created. I've attempted to find a way to indirectly call the constructor, but to no avail. Any suggestion would be great. The code compiles and runs fine on Windows. if (x == 1){ cout <<"MODE SELECTED: IMAGE TESTING \n"; ImageProcessor*

问题 I am struggling to understand the constructor invocation pattern in Javascript. I have a base object Mammal ( would it be incorrect to use the term class ? ) and an inherited object Cat . In the following code the object Cat correctly inherits from the Mammal object. /* Mammal base Object */ var Mammal = function(name) { this.name = name; } Mammal.prototype.get_name = function() { return this.name; } Mammal.prototype.says = function () { return this.saying || ''; } /* Cat object */ var Cat =

问题 I have a model like this: class Person(models.Model,Subject): name = .. The class Subject is not supposed to be in the Database so, it doesn't extends from models.Model: class Subject: def __init__(self,**kargs): _observers = [] my problem is that the constructor of Subject is never called , so i've tried adding this to the class Person: def __init__(self): super(Person,self).__init__() but now i have an error saying that init takes 1 arguments but 7 are given, and the only thing i'm doing is

问题 I was working on one my projects, and while I was making the constructor for a class, I was setting some of my variables to a default value. I went to set an std::string to NULL , and it gave me an error. But when I define an std::string and set it to NULL on the same line, it works without any errors. I was wondering why First Example std::string text = NULL; worked, and Second Example std::string text; text = NULL; didn't work. Now I know you shouldn't set a string to NULL, or 0, but I