constructor

问题 In the code below I receive the compile error Error Too many arguments to 'Public Sub New()' on the Dim TestChild As ChildClass = New ChildClass("c") . I do not receive it on TestChild.Method1() even though they are both on the base class I am inheriting from. Public Class BaseClass Public ReadOnly Text As String Public Sub New(ByVal SetText As String) Text = SetText End Sub Public Sub New() Text = "" End Sub End Class Public Class ChildClass Inherits BaseClass End Class Public Class

问题 In a Java class with static instance fields, is the constructor called every time the fields are accessed, or only on the first access? I initialize the static fields in the constructor, and was wondering if this would cause a slow down because the fields are initialized on every access. 回答1: I initialize the static fields in the constructor, Don't . Never initialize static fields inside a constructor. static fields are not something associated with any instance of a class. It is bound to

问题 This question already has an answer here : How to call the constructor with call_user_func_array in PHP (1 answer) Closed 4 years ago . I have searched many a page of Google results as well as here on stackoverflow but cannot find a solution that seems to fit my situation. I appear to have but one last snag in the function I am trying to build, which uses call_user_func_array to dynamically create objects. The catchable fatal error I am getting is Object of class Product could not be

问题 I'm not really sure why my application won't start up, I get no errors and I have no idea what's going on? I'm pretty new to android and this is just a basic calculator, but it keeps crashing every time I start it up. ***************Main Activity.java********************** package com.example.alex.myapplication; import android.support.v7.app.ActionBarActivity; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; public class MainActivity extends ActionBarActivity

问题 I am trying to rewrite my code from one big function to oop. If I have this, it crash on session.add(a1) # Unresolved reference : from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import * from sqlalchemy.orm import * Base = declarative_base() class Address(Base): __tablename__ = 'address' id = Column(Integer, primary_key=True) street = Column(String, nullable=False) city = Column(String, nullable=False) user = relationship('User', back_populates="address") class Main():

问题 I am learning constructors and Destructors in c++; Help me grasp my mistakes even if they are silly... HERE is a code I have written to perform addition using classes in c++; This creates two summands of datatype num and employs the constructor sum() to perform sum of the two numbers; However when everything was goin' alright, I stumbled upon creating a copy constructor for num , (Although not necessary but still for practice)... without the dynamic object of the class sum it is not possible

问题 This question already has answers here : Assigning variables with dynamic names in Java (7 answers) Closed 5 years ago . Trying to get a better understanding of Swing and AWT with constructors, but now I have a question about constructors. Based on whether or not the boolean maximize is true I want to set a new public boolean variable with the same value. Thing is I might need multiple JFrames but I can't have the same public variable name created if true. How do I instantiate a boolean with

问题 my constructor gets ignored somehow. Here is my code: My class: class field { private: char PlayField[5][5]; public: char o = 'o'; field() { char PlayField[5][5] = { { o, o, o, o, o }, { o, o, o, o, o }, { o, o, o, o, o }, { o, o, o, o, o }, { o, o, o, o, o } }; } void setTile(int x_val, int y_val) { PlayField[x_val][y_val] = 'x'; } char getTile(int x_val, int y_val) { return PlayField[x_val][y_val]; } /*field::~field();*/ }; The constructor field() should initalize my 4 wins field with 'o's

问题 I have this class: public class Book extends SugarRecord { private Long id; private String mBookName; private String mAuthorName; private List<Page> mPageList; public Book() { } public Book(String bookname, String authorName) { mBookName = bookname; mAuthorName = authorName; mPageList = new ArrayList<>(); } public Book(String bookname, String authorName, List<Page> pageList) { mBookName = bookname; mAuthorName = authorName; mPageList = pageList; } @Override public Long getId() { return id; }

问题 I've read through some of the other posts that are related but I don't believe I have the same problem that they do. I believe I'm doing my constructor for my inherited class properly, however it still won't work - and won't even recognize that I have a constructor there it seems. class BlockedNumber : PhoneNumber { public BlockedNumber(string a, string m, string l) : base(a, m, l) { } } This still gives me the error in the title: "DTS.PhoneNumber does not contain a constructor that takes 0