106 questions
3
votes
2
answers
201
views
Can I dynamically generate a contiguous sequence of non-default-ctorable objects which can be deleted with delete[]?
Suppose I have:
Identifier
Meaning
T
a non-default-constructible class
gen
a function returning a T
n
a positive size_t value
Now, I want to generate n T-objects, using gen, consecutively on the ...
- 130k
3
votes
1
answer
102
views
explicit deleted constructors - does this matter?
When marking a constructor as deleted, i.e.
class MyClass {
// ...
MyClass(int x) = delete;
// ...
};
is there any effect to marking the deleted constructor as explicit? i.e.
...
- 130k
13
votes
3
answers
2k
views
Is it legal to initialize an array via a functor which takes the array itself as a parameter by reference?
In the question Idiom for initializing an std::array using a generator function taking the index?,which basically asks how one can initialize an array of an arbitrary type which is not necessarily ...
- 4,876
3
votes
0
answers
71
views
How come I can capture an object being constructed in the lambda doing the construction? [duplicate]
Consider the following code:
int x = [&x](){
std::cout << "Inside lambda, x is " << x << '\n';
x = 5;
return 23;
}();
std::cout << "x is " &...
- 130k
7
votes
2
answers
574
views
Idiom for initializing an std::array using a generator function taking the index?
Suppose I have a function T foo(size_t i). What would be an elegant and succinct way of constructing an object arr, of type std::array<T, N>, so that we have arr[i] == foo(i)?
If possible, I ...
- 130k
0
votes
1
answer
192
views
Snowflake query to create json - multiple results for single attribute
I have a table in snowflake that has three different columns being used as name type/values. These need to be mapped in an MDM tool using json. Of course, I cannot use the same attribute name more ...
- 25
0
votes
1
answer
96
views
Constructing lambdas in constructors
I had some nasty bugs when constructing lambdas in constructors when working with callback-based event system.
Here's simple scenario:
class Object {
public:
int variable = 10;
std::function&...
- 79
0
votes
0
answers
33
views
Trouble constructing a map with immovable value types from initializer list [duplicate]
Consider the following code:
#include <map>
#include <type_traits>
#include <memory>
void foo() {
using map_type = std::map<int, std::unique_ptr<float[]>>;
auto ...
- 130k
1
vote
2
answers
230
views
Using a method to create objects
I have a question regarding creating object using a method, please see my code below:
import java.util.ArrayList;
import java.util.Scanner;
public class Student {
private String name;
private ...
- 71
0
votes
0
answers
41
views
Calling multiple async operations in a C# class initializer
Given a C# class like this
public class MyData
{
public int Value1 { get; set; }
public int Value2 { get; set; }
}
Could it ever create a concurrency problem to instantiate and initialize ...
- 11
0
votes
1
answer
61
views
Mocking object construction in unit tests
I would like to write unit tests for a class which creates an instance of a problematic class, and I am working under the following constraints:
My class calls some third-party library initialization ...
- 7,784
5
votes
1
answer
770
views
Why does object.__new__ accept parameters?
Besides the obvious asking "again" about __new__ and __init__ in Python - I can ensure, I know what it does. I'll demonstrate some strange and to my opinion undocumented behavior, for which ...
- 16.1k
0
votes
1
answer
253
views
Python Factory Method Suggestions
I would like to ask you to help me out with my factory method. I have to handle multiple and periodic csv objects, each of which has its own properties, thus its own class. The only way I can tell ...
- 47
1
vote
1
answer
56
views
How can I create new objects with user defined properties every time a function is called in JavaScript?
Apologies if this is a stupid question, I'm very much a beginner here.
I run a D&D game, and I thought a good thing to practice coding with would be a simple initiative tracker.
At the moment, I'm ...
- 15
1
vote
1
answer
448
views
Why does std::map crash when it is declared static inline inside a class and used early?
I have found several times that when a std::map is declared inside a class as a static inline (C++ 17),
struct MyStruct
{
static inline std::map <A, B> mymap;
MyStruct(A& a, B& ...
- 157
0
votes
3
answers
100
views
object Object being written [duplicate]
I am very new to JS and am playing around trying to output this verify function I came across below.
In my limited thinking I thought that the result would be false and I would be able to write that ...
0
votes
2
answers
39
views
The value returned for a newly constructed object returns the value of the previously created one
I have the following challenge for practicing OOP in javascript:
The Bank should allow us to:
Add customers
A customer should be able to deposit an amount.
A customer should bevable to withdraw an ...
- 103
0
votes
1
answer
102
views
Should a java constructor contain logic to build itself? [duplicate]
I'm working on a java project where I take in some JSON objects and have to then go through them to create a domain object that I need to then further process. Currently the constructor of this object ...
- 611
3
votes
2
answers
98
views
F# Object Tree Syntax
In C# it is possible to construct object trees in a rather succint syntax:
var button = new Button() { Content = "Foo" };
Is there an idiomatic way to do something similar in F#?
Records ...
- 5,692
0
votes
1
answer
151
views
How are objects from derived classes constructed in C++
Im not a C++ pro, i've done mostly Java and C#. A teacher said something that confused me today. I've tried to validate the info by doing some research, but i ended up even more confused.
Lets say i ...
0
votes
0
answers
175
views
What is the difference between object creation and object initialization in C++?
This section of Richard Smith’s paper Guaranteed copy elision through simplified value categories makes an important distinction between object creation and object initialization (prvalues were ...
- 7,890
0
votes
1
answer
291
views
Can I call the garbage collector early in matlab?
In matlab, I have a class that ties up a shared resource during construction and releases it when deleted. (In my specific case, the shared resource is a port I can interact with it via http://...
- 1,050
2
votes
3
answers
193
views
Do we really need placement new-expressions?
I am trying to understand placement new-expressions in C++.
This Stack Overflow answer states that T* p = new T(arg); is equivalent to
void* place = operator new(sizeof(T)); // storage allocation
T* ...
- 7,890
0
votes
0
answers
27
views
How do I correctly construct a new Python object? [duplicate]
Apologies for the slightly vague question, but I'm not too sure how to word it.
The following very basic code example isn't doing what I'd expect it do, and I'd like to understand why...
class Message(...
- 133
2
votes
1
answer
134
views
What's the difference between push_back({ "George", 1 }) and push_back(Student("Jack", 10));
I was just wondering if there's a difference between the following two lines:
objStudents.push_back({ "George", 1 });
objStudents.push_back(Student("Jack", 10));
Is one way more ...
1
vote
0
answers
18
views
working of universal initialization causing destructor to be called one extra time [duplicate]
#include<iostream>
#include<vector>
class test {
public:
virtual ~test()
{
std::cout<<"...
- 11
0
votes
0
answers
50
views
Javascript examples from Duckett's book not working
I am learning javascript from Duckett's book and have noticed that the examples from the book were not working when I copied them onto my text edit.
The code is on the website so, I downloaded the ...
1
vote
2
answers
102
views
constructing object from temporary
I'm using a third-party class with (only) constructor as follows
class foo // cannot be altered
{
public:
explicit foo(std::istream&);
...
};
and the documentation of which suggests the ...
- 45.3k
3
votes
4
answers
5k
views
how to maintain order of elements using snowflake object_construct() function instead of sorting by the keys?
Following snowflake query returns the JSON structure but output is sorted by the keys. How not to sort by the keys but retains the order? Is there any parameter setting that needs to be set?
select
...
- 31
0
votes
1
answer
117
views
How to enforce that construction is always through a certain method?
I have some third-party abstract base class
struct foo
{
virtual foo*job() = 0;
...
static void* make_space(size_t sizeofDerived);
};
which I cannot alter. Objects of type foo (and all ...
- 45.3k
3
votes
1
answer
2k
views
Kotlin: How do you make a new instance of a data class with changes
I have a kotlin data class:
data class MyCats (
) {
val name: String = "",
val female: Boolean = false,
val fixed: Boolean = false
}
As I understand Kotlin (still a newbie), I ...
- 11.6k
11
votes
1
answer
694
views
What is the purpose for std::construct_at to cast through a pointer to volatile when using placement new?
According to cppreference, std::construct_at(T*p, Args&&... args) is equivalent to
return ::new (const_cast<void*>(static_cast<const volatile void*>(p)))
T(std::forward<Args&...
- 45.3k
-2
votes
1
answer
77
views
why do i not return anything from my constructor function?
function Person (name, eyeColor, age) {
this.name = name;
this.eyeColor = eyeColor;
this.age = age;
this.updateAge = function () {
return ++this.age;
};
}
let person1 = new Person("kevin&...
user13752749
5
votes
3
answers
301
views
How to make an object constructor in JavaScript;
Could you please explain me what's wrong in the following code?
function box (width, height, color) {
this.width=width;
this.height=height;
this.color=color;
this.style.width=width;
...
1
vote
2
answers
56
views
how to get the member in C++ struct initialization
struct Test {
int w, h;
int * p;
};
int main(){
Test t {
10,
20,
new int[this->h*this->w]
};
return 0;
}
I just want to use the w and h in ...
- 151
-2
votes
1
answer
270
views
Problem constructing a base class from within a subclass constructor
I have 2 classes. Since Doctor will be considered as Employee, I should be using Employee class functions in Doctor class. Only extra thing that Doctor class has is TITLE. Basically, What I tried is I ...
- 33
0
votes
2
answers
216
views
Reconstructing JSON with jq
I have a JSON like this (sample.json):
{
"sheet1": [
{
"hostname": "sv001",
"role": "web",
"ip1": "172.17.0.3"
},
{
"hostname": "sv002",
"role": "web",
...
- 13
0
votes
1
answer
1k
views
Lombok: How to define a special method which runs upon the Object construction?
I have a @Value @AllArgsConstructor class, and I want each instance of it to have an ID(The first object has the ID of 1, the second is 2, etc..).
until now, before I used lombok but a constructor, my ...
- 21
1
vote
1
answer
100
views
How do I include a previously declared function as a value in a key-value pair in an object constructor?
The task:
declare a variable called myName that returns an array of two elements, firstname and last name.
declare a function called join(), it will return the two elements as a string with a space ...
4
votes
3
answers
1k
views
Java bad practice doing: new... ().doSomething()?
I just saw a piece of code that had some classes with only one method. I picked an examples:
public class TempDirCleanupProcess {
public void cleanup(final File directory) {}
}
Then, later on in ...
- 2,369
1
vote
1
answer
440
views
How usage of member initializer list prevents creation of redundant object in c++? [duplicate]
I have a question regarding difference in initializing an object with and without constructor member initializer list.
In the following code snippet there are two classes Test1 and Test2 each with ...
- 607
0
votes
2
answers
622
views
Function Constructor - add function using prototype gives - Uncaught SyntaxError: Unexpected token {
I tried adding a function y() into the object constructor x using prototype chaining. It results to an unexpected error:
Unexpected token {
function x(a, b) {
this.a = a
this.b = b
}
...
- 1,086
1
vote
1
answer
229
views
Is it possible to limit the number of instances of a class at compile time?
Assume there is a class Foo that I, as the designer of a library, do not want my users to be able to instantiate more than n amount of times (where n is not necessarily 1).
Is there any way to enforce ...
- 163
2
votes
3
answers
2k
views
The Scope of Creating an instance of a class inside a method in java
Can anyone explain to me the scope of creating an object from a class inside a method in java, is it a bad way and wasting the resources or it's normal? The program is running but I am not sure about ...
- 71
0
votes
1
answer
497
views
QML: object instantiation
Is there a way to have a mechanism similar to Component.createObject's second argument (initial properties) with a Loader element? I'm setting the properties manually in onLoaded, but this has ...
- 7,749
1
vote
0
answers
35
views
varadic argument templated object creation on container not working
Below is a example (not the entire class, just relevant parts)
class Container {
private:
size_t m_next_id;
std::unordered_map m_objects;
public:
template<typename Type, typename... ...
- 654
0
votes
1
answer
203
views
How do I name an Object inside of an Object Constructor someone's Discord Username?
I am trying to create an object constructor in a JSON file for Discord. The large constructor is named "person" and I want the objects inside of that to be the Discord Message Author's name, but I can'...
- 13
-3
votes
2
answers
77
views
Representing a value which can't be ctor-initialization-list initialized
I'm writing a class C with a member foo of type foo_t. This member must be defined and valid throughout the liftime of a C instance; however, I don't have the necessary information to construct it at ...
- 130k
14
votes
2
answers
10k
views
std::initializer_list constructor
In code like this:
#include <iostream>
#include <initializer_list>
#include <string>
struct A
{
A() { std::cout << "2" << std::endl; }
A(int a) { std::cout <&...
- 1,196
-1
votes
2
answers
370
views
Delete object's variable after instantiation
So I have an object which needs certain variables to be instantiated. These variables are passed to the object through an array of objects. Then, each element in the array gets assigned to an internal ...
- 138