class

问题 I have a function which is supposed to return an array of class type. So from database I picked data and filled datatable. Now from datatable I am picking columns value and assigning to the properties of the class. But problem is that what I am doing will assign a single record only but I want to fill the class type array with multiple record. My code: Private Sub BindGridInfoFunctionalLocation() Dim v_ObjDs As New DataSet Try v_ObjDs = v_ObjBREngine.FetchSqlDS("select FunctionalLocation as

问题 I have a function which is supposed to return an array of class type. So from database I picked data and filled datatable. Now from datatable I am picking columns value and assigning to the properties of the class. But problem is that what I am doing will assign a single record only but I want to fill the class type array with multiple record. My code: Private Sub BindGridInfoFunctionalLocation() Dim v_ObjDs As New DataSet Try v_ObjDs = v_ObjBREngine.FetchSqlDS("select FunctionalLocation as

问题 I'm trying to figure out why I'm getting the following error: error: redefinition of 'TimeDuration' // TimeDuration.cpp #define HOUR 3600 #define MIN 60 #include <iostream> #include <string> #include "TimeDuration.h" using namespace std; TimeDuration::TimeDuration() { seconds = 0; } void TimeDuration::setDuration(const int sec) { seconds = sec; } void TimeDuration::display() { // Some code to display the time } The error is showing in my header file. // TimeDuration.h class TimeDuration {

问题 I'm trying to figure out why I'm getting the following error: error: redefinition of 'TimeDuration' // TimeDuration.cpp #define HOUR 3600 #define MIN 60 #include <iostream> #include <string> #include "TimeDuration.h" using namespace std; TimeDuration::TimeDuration() { seconds = 0; } void TimeDuration::setDuration(const int sec) { seconds = sec; } void TimeDuration::display() { // Some code to display the time } The error is showing in my header file. // TimeDuration.h class TimeDuration {

问题 I am currently trying to get a two body problem to work, that I can then upgrade to more planets, but it is not working. It is outputting me impossible positions. Does anyone know what is causing that? This is the code I use: day = 60*60*24 # Constants G = 6.67408e-11 dt = 0.1*day au = 1.496e11 t = 0 class CelBody: def __init__(self, id, name, x0, y0, z0, vx0, vy0, vz0, mass, vector, ax0, ay0, az0, totalforcex, totalforcey, totalforcez): self.ax0 = ax0 self.ay0 = ay0 self.az0 = az0 self.ax =

问题 Does Python have a mechanism for class constructors, i.e. a function that is called whenever the class is first referenced (as opposed to when an instance of that object is created)? I know this exists in some other languages, but I haven't come across it in Python. Basically, I would like to initialise some static attributes in that function. I put an example below of what I would expect. Of course, the example returns None, but I would like it return 'foo'. class T: arg = None def __class

问题 So I'm trying to run a particular file called CountdownTree.java that inherits functions from a bunch of other files in the package comp2402a4. These were all starting files given by my instructor that I'm supposed to add to, and there shouldn't be any errors running these files. I compiled it using 'javac comp2402a4/CountdownTree.java' and it compiled fine with no problems. But when I try to run it using 'java comp2402a4/CountdownTree.java', I get the error: Exception in thread "main" java

问题 I have always this question burning in me. Why do people assign objects of subclass to a superclass reference as below: What exactly are the benefits and reasons that makes people do so? public static void main(String[] args) { A obj1 = new C(); //Why do this ? C obj2 = new C(); //When we can simply do this ??? } class A {} class B extends A {} class C extends B {} I understands all the logic where a Class Dog is an Animal but Animals are not essentially Dogs. I've also bumped into this link:

问题 Assume you define a class, which has a method which does some complicated processing: class A(object): def my_method(self): # Some complicated processing is done here return self And now you want to use that method on some object from another class entirely. Like, you want to do A.my_method(7) . This is what you'd get: TypeError: unbound method my_method() must be called with A instance as first argument (got int instance instead) . Now, is there any possibility to hack things so you could

问题 To give you some context, yesterday I came across this post. I found the problem quite interesting, so I tried to find a solution that would keep the syntax as close as possible to what was asked. Here is what I came up with: class DummyCube: cubes = [] @classmethod def __getattribute__(cls, name): print('is this called?') attributes = [getattr(cube, name) for cube in cls.cubes] return attributes class Cube: def __init__(self, volume): DummyCube.cubes.append(self) self.volume = volume a =