Construction.md

Construction

Constructing otn tokens is similar to constructing smart pointers from the C++ STL.

See the Synopsis for token's constructors and factory functions.

Itself constructors

itself constructor

template <class ... Args>
explicit token(itself_t, Args&& ... args);

Constructs a token<T> that creates an object of type T, initialized as if direct-initializing from the arguments std::forward<Args>(args)....

Example

#include <otn/all.hpp>
#include <iostream>

class Foo
{
public:
    explicit Foo(int value) : m_value{value} {}
    int value() const { return m_value; }

private:
    int m_value;
};

int main()
{
    using namespace otn;

    // Constructing a, b and c are equivalent.
    unique<Foo> a{itself, 7};
    unique<Foo> b{new Foo(7)};
    auto c = make_unique<Foo>(7);

    std::cout << "a: " << (*a).value() << std::endl;
    std::cout << "b: " << (*b).value() << std::endl;
    std::cout << "c: " << (*c).value() << std::endl;
}

Output:

a: 7
b: 7
c: 7

itself_type constructor

template <class Y, class ... Args>
explicit token(itself_type_t<Y>, Args&& ... args);

Constructs a token<T> that creates an object of type Y, initialized as if direct-initializing from the arguments std::forward<Args>(args)....

Example

#include <otn/all.hpp>
#include <iostream>

class Foo
{
public:
    virtual int value() const = 0;

    virtual ~Foo() = default;
};

class Bar : public Foo
{
public:
    explicit Bar(int value) : m_value{value} {}
    int value() const override { return m_value; }

private:
    int m_value;
};

int main()
{
    using namespace otn;

    // Constructing a, b and c are equivalent.
    unique<Foo> a{itself_type<Bar>, 7};
    unique<Foo> b{new Bar(7)};
    unique<Foo> c = make_unique<Bar>(7);

    std::cout << "a: " << (*a).value() << std::endl;
    std::cout << "b: " << (*b).value() << std::endl;
    std::cout << "c: " << (*c).value() << std::endl;
}

Output:

a: 7
b: 7
c: 7