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Why do I need to provide constructor implementation in header? C++


By : Rezam Alkhaldi
Date : July 31 2020, 03:00 PM
Does that help You declared 2 classes with same name, your cpp is completely wrong. It does not contain implementation of constructor declared in hpp file, it declares another class and it's implementation. main.cpp includes hpp file and look for implementation which does not exists.
So at first never use reserved keywords as names! test.hpp:
code :
#pragma once
#include <string>
class Test{
public:
    std::string name;
    Test(std::string name);
};
#include "test.hpp"

Test::Test(std::string name)
{
    this->name = name;
}


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Constructor in implementation versus header


By : user3757828
Date : March 29 2020, 07:55 AM
Hope that helps The constructor should, to my knowledge, be defined in the implementation file but I've only been able to find examples with the class inside one main file instead of split into a .h and .cpp file
code :
cEntity::cEntity (int x, int y, int height, int width) {
   X,Y,Height,Width = new int;
   X = new int(x);
   Y = new int(y);
   Height = new int(height);
   Width = new int(width);
cEntity::cEntity (int x, int y, int height, int width) {
    :X(new int(x))
    ,Y(new int(y))
    ,Height(new int(height))
    ,Width(new int(width))
{}

Does an available compiler provide an implementation of the C11 '_Atomic' keyword and its related header 'stdatomic.h'?


By : Mikołaj Trawiński
Date : March 29 2020, 07:55 AM

Is it okay to provide the definition of a constructor inside the header file that declares it?


By : Janysson Silva
Date : March 29 2020, 07:55 AM
With these it helps Yes, you can define constructors in the header file, typically inside the class definition itself as you have been doing.
No, it isn't necessarily poor practice. For example, it is probably silly to create a cpp file just to put the constructor definition somewhere other than the header, if the constructor is short and simple.

Can I provide an incomplete header for a C++ class to hide the implementation details?


By : user3234729
Date : March 29 2020, 07:55 AM
it should still fix some issue The short answer is "No!"
The reason: any/all 'client' projects that need to use your Class class have to have the full declaration of that class, in order that the compiler can properly determine such things as offsets for member variables.
code :
// impl.h
struct MyInternal; // An 'opaque' structure - the definition is For Your Eyes Only
class Class {
public:
    Class();
    init();
    doSomething();
private:
    MyInternal* hidden; // CLient never needs to access this! Compiler error if attempted.
}

// impl.cpp
#include <api.h>
#include <impl.h>

struct MyInternal {
    SomeLibrary::Type myData;
};

Class::Class() {
    init();
}
Class::init() {
    hidden = new MyInternal; // MUCH BETTER TO USE unique_ptr, or some other STL.
    hidden->myData = SomeLibrary::Type(42);
}
Class::doSomething() {
    hidden->myData.doSomething();
}

Getting 'Context is not constructible. Add a default constructor or provide an implementation of IDbContextFactory."


By : Nicholas Phillips
Date : March 29 2020, 07:55 AM
Any of those help Essentially you need a default ctor (that's the error) - but just implementing it would lead to problems.
You'd have to implement the IDbContextFactory for the results to be consistent (or your migration from code won't work etc.).
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