Implementing the singleton pattern [closed]

-1

using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};



    public:

    PersonA* createInstance(){

        cout << "Instance created" << endl;

        return new PersonA;

    };

};



int main()

{

    PersonA* Hello = PersonA::createInstance();

    return 0;

}

My IDE is giving me an error which says:
Call to non static member function without an argument
I dont understand why this method requires an argument?
Am i missing something?

asked Jan 1 at 5:20

LuckyBlue

closed as off-topic by Sneftel, t.niese, Raedwald, DebanjanB, zx485 Jan 1 at 20:55

This question appears to be off-topic. The users who voted to close gave this specific reason:

"This question was caused by a problem that can no longer be reproduced or a simple typographical error. While similar questions may be on-topic here, this one was resolved in a manner unlikely to help future readers. This can often be avoided by identifying and closely inspecting the shortest program necessary to reproduce the problem before posting." – Sneftel, t.niese, zx485

If this question can be reworded to fit the rules in the help center, please edit the question.

1

createInstance is not a static function so you cant call it without an object.

– user1438832
Jan 1 at 5:22

ohhhhhhh, thank you

– LuckyBlue
Jan 1 at 5:24

I am abit drunk, but thank you

– LuckyBlue
Jan 1 at 5:24

How come is this a singleton pattern?

– Kunal Puri
Jan 1 at 5:27

It is beginning to look like a singleton pattern

– LuckyBlue
Jan 1 at 5:30

|
show 1 more comment

-1

using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};



    public:

    PersonA* createInstance(){

        cout << "Instance created" << endl;

        return new PersonA;

    };

};



int main()

{

    PersonA* Hello = PersonA::createInstance();

    return 0;

}

My IDE is giving me an error which says:
Call to non static member function without an argument
I dont understand why this method requires an argument?
Am i missing something?

asked Jan 1 at 5:20

LuckyBlue

closed as off-topic by Sneftel, t.niese, Raedwald, DebanjanB, zx485 Jan 1 at 20:55

This question appears to be off-topic. The users who voted to close gave this specific reason:

"This question was caused by a problem that can no longer be reproduced or a simple typographical error. While similar questions may be on-topic here, this one was resolved in a manner unlikely to help future readers. This can often be avoided by identifying and closely inspecting the shortest program necessary to reproduce the problem before posting." – Sneftel, t.niese, zx485

If this question can be reworded to fit the rules in the help center, please edit the question.

1

createInstance is not a static function so you cant call it without an object.

– user1438832
Jan 1 at 5:22

ohhhhhhh, thank you

– LuckyBlue
Jan 1 at 5:24

I am abit drunk, but thank you

– LuckyBlue
Jan 1 at 5:24

How come is this a singleton pattern?

– Kunal Puri
Jan 1 at 5:27

It is beginning to look like a singleton pattern

– LuckyBlue
Jan 1 at 5:30

|
show 1 more comment

-1

using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};



    public:

    PersonA* createInstance(){

        cout << "Instance created" << endl;

        return new PersonA;

    };

};



int main()

{

    PersonA* Hello = PersonA::createInstance();

    return 0;

}

My IDE is giving me an error which says:
Call to non static member function without an argument
I dont understand why this method requires an argument?
Am i missing something?

asked Jan 1 at 5:20

LuckyBlue

using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};



    public:

    PersonA* createInstance(){

        cout << "Instance created" << endl;

        return new PersonA;

    };

};



int main()

{

    PersonA* Hello = PersonA::createInstance();

    return 0;

}

My IDE is giving me an error which says:
Call to non static member function without an argument
I dont understand why this method requires an argument?
Am i missing something?

c++

asked Jan 1 at 5:20

LuckyBlue

asked Jan 1 at 5:20

LuckyBlue

asked Jan 1 at 5:20

LuckyBlue

asked Jan 1 at 5:20

LuckyBlue

asked Jan 1 at 5:20

LuckyBlue

closed as off-topic by Sneftel, t.niese, Raedwald, DebanjanB, zx485 Jan 1 at 20:55

This question appears to be off-topic. The users who voted to close gave this specific reason:

"This question was caused by a problem that can no longer be reproduced or a simple typographical error. While similar questions may be on-topic here, this one was resolved in a manner unlikely to help future readers. This can often be avoided by identifying and closely inspecting the shortest program necessary to reproduce the problem before posting." – Sneftel, t.niese, zx485

If this question can be reworded to fit the rules in the help center, please edit the question.

closed as off-topic by Sneftel, t.niese, Raedwald, DebanjanB, zx485 Jan 1 at 20:55

This question appears to be off-topic. The users who voted to close gave this specific reason:

"This question was caused by a problem that can no longer be reproduced or a simple typographical error. While similar questions may be on-topic here, this one was resolved in a manner unlikely to help future readers. This can often be avoided by identifying and closely inspecting the shortest program necessary to reproduce the problem before posting." – Sneftel, t.niese, zx485

If this question can be reworded to fit the rules in the help center, please edit the question.

1

createInstance is not a static function so you cant call it without an object.

– user1438832
Jan 1 at 5:22

ohhhhhhh, thank you

– LuckyBlue
Jan 1 at 5:24

I am abit drunk, but thank you

– LuckyBlue
Jan 1 at 5:24

How come is this a singleton pattern?

– Kunal Puri
Jan 1 at 5:27

It is beginning to look like a singleton pattern

– LuckyBlue
Jan 1 at 5:30

|
show 1 more comment

1

createInstance is not a static function so you cant call it without an object.

– user1438832
Jan 1 at 5:22

ohhhhhhh, thank you

– LuckyBlue
Jan 1 at 5:24

I am abit drunk, but thank you

– LuckyBlue
Jan 1 at 5:24

How come is this a singleton pattern?

– Kunal Puri
Jan 1 at 5:27

It is beginning to look like a singleton pattern

– LuckyBlue
Jan 1 at 5:30

createInstance is not a static function so you cant call it without an object.

– user1438832
Jan 1 at 5:22

ohhhhhhh, thank you

– LuckyBlue
Jan 1 at 5:24

I am abit drunk, but thank you

– LuckyBlue
Jan 1 at 5:24

How come is this a singleton pattern?

– Kunal Puri
Jan 1 at 5:27

It is beginning to look like a singleton pattern

– LuckyBlue
Jan 1 at 5:30

|
show 1 more comment

2 Answers
2

active

oldest

votes

static is missing.

but you don't implement singleton pattern currently, if you want to, use Meyers' one:

class PersonA

{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}

public:

    PersonA(const PersonA&) = delete;

    PersonA& operator =(const PersonA&) = delete;



    static PersonA& getInstance(){

        static PersonA instance{};

        return instance;

    }

};

But maybe you just want a factory method, then avoid raw owning pointer, and use smart pointer:

class PersonA{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}



public:

    std::unique_ptr<PersonA> create()

    {

        std::cout << "Instance created" << std::endl;

        return std::make_unique<PersonA>();

    }

};

edited Jan 1 at 17:15

answered Jan 1 at 9:12

Jarod42

118k12103188

add a comment |

you can do it like -

#include <iostream>



using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};

    static PersonA* p;

    public:

    static PersonA* createInstance(){

        if(p == nullptr)

        {

            cout << "Instance created" << endl;

            p= new PersonA();

        }

        return p;

    };

};



PersonA* PersonA::p=nullptr;



int main()

{

    PersonA* A = PersonA::createInstance();

    PersonA* B = PersonA::createInstance();

    return 0;

}

answered Jan 1 at 5:29

user1438832

39318

Thank you thank you, god bless. Happy new year

– LuckyBlue
Jan 1 at 5:31

Attempting to code when drunk is not good

– LuckyBlue
Jan 1 at 5:31

But happy new year anyway!!

– LuckyBlue
Jan 1 at 5:31

BIG UP MAN!!!!!!!

– LuckyBlue
Jan 1 at 5:42

You will also want to delete the copy constructor and assignment operator.

– user4581301
Jan 1 at 5:44

|
show 1 more comment

2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

static is missing.

but you don't implement singleton pattern currently, if you want to, use Meyers' one:

class PersonA

{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}

public:

    PersonA(const PersonA&) = delete;

    PersonA& operator =(const PersonA&) = delete;



    static PersonA& getInstance(){

        static PersonA instance{};

        return instance;

    }

};

But maybe you just want a factory method, then avoid raw owning pointer, and use smart pointer:

class PersonA{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}



public:

    std::unique_ptr<PersonA> create()

    {

        std::cout << "Instance created" << std::endl;

        return std::make_unique<PersonA>();

    }

};

edited Jan 1 at 17:15

answered Jan 1 at 9:12

Jarod42

118k12103188

add a comment |

static is missing.

but you don't implement singleton pattern currently, if you want to, use Meyers' one:

class PersonA

{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}

public:

    PersonA(const PersonA&) = delete;

    PersonA& operator =(const PersonA&) = delete;



    static PersonA& getInstance(){

        static PersonA instance{};

        return instance;

    }

};

But maybe you just want a factory method, then avoid raw owning pointer, and use smart pointer:

class PersonA{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}



public:

    std::unique_ptr<PersonA> create()

    {

        std::cout << "Instance created" << std::endl;

        return std::make_unique<PersonA>();

    }

};

edited Jan 1 at 17:15

answered Jan 1 at 9:12

Jarod42

118k12103188

add a comment |

static is missing.

but you don't implement singleton pattern currently, if you want to, use Meyers' one:

class PersonA

{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}

public:

    PersonA(const PersonA&) = delete;

    PersonA& operator =(const PersonA&) = delete;



    static PersonA& getInstance(){

        static PersonA instance{};

        return instance;

    }

};

But maybe you just want a factory method, then avoid raw owning pointer, and use smart pointer:

class PersonA{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}



public:

    std::unique_ptr<PersonA> create()

    {

        std::cout << "Instance created" << std::endl;

        return std::make_unique<PersonA>();

    }

};

edited Jan 1 at 17:15

answered Jan 1 at 9:12

Jarod42

118k12103188

static is missing.

but you don't implement singleton pattern currently, if you want to, use Meyers' one:

class PersonA

{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}

public:

    PersonA(const PersonA&) = delete;

    PersonA& operator =(const PersonA&) = delete;



    static PersonA& getInstance(){

        static PersonA instance{};

        return instance;

    }

};

But maybe you just want a factory method, then avoid raw owning pointer, and use smart pointer:

class PersonA{

private:

    PersonA() { std::cout << "PersonA constr called" << std::endl;}



public:

    std::unique_ptr<PersonA> create()

    {

        std::cout << "Instance created" << std::endl;

        return std::make_unique<PersonA>();

    }

};

edited Jan 1 at 17:15

answered Jan 1 at 9:12

Jarod42

118k12103188

edited Jan 1 at 17:15

answered Jan 1 at 9:12

Jarod42

118k12103188

answered Jan 1 at 9:12

Jarod42

118k12103188

answered Jan 1 at 9:12

Jarod42

118k12103188

add a comment |

you can do it like -

#include <iostream>



using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};

    static PersonA* p;

    public:

    static PersonA* createInstance(){

        if(p == nullptr)

        {

            cout << "Instance created" << endl;

            p= new PersonA();

        }

        return p;

    };

};



PersonA* PersonA::p=nullptr;



int main()

{

    PersonA* A = PersonA::createInstance();

    PersonA* B = PersonA::createInstance();

    return 0;

}

answered Jan 1 at 5:29

user1438832

39318

Thank you thank you, god bless. Happy new year

– LuckyBlue
Jan 1 at 5:31

Attempting to code when drunk is not good

– LuckyBlue
Jan 1 at 5:31

But happy new year anyway!!

– LuckyBlue
Jan 1 at 5:31

BIG UP MAN!!!!!!!

– LuckyBlue
Jan 1 at 5:42

You will also want to delete the copy constructor and assignment operator.

– user4581301
Jan 1 at 5:44

|
show 1 more comment

you can do it like -

#include <iostream>



using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};

    static PersonA* p;

    public:

    static PersonA* createInstance(){

        if(p == nullptr)

        {

            cout << "Instance created" << endl;

            p= new PersonA();

        }

        return p;

    };

};



PersonA* PersonA::p=nullptr;



int main()

{

    PersonA* A = PersonA::createInstance();

    PersonA* B = PersonA::createInstance();

    return 0;

}

answered Jan 1 at 5:29

user1438832

39318

Thank you thank you, god bless. Happy new year

– LuckyBlue
Jan 1 at 5:31

Attempting to code when drunk is not good

– LuckyBlue
Jan 1 at 5:31

But happy new year anyway!!

– LuckyBlue
Jan 1 at 5:31

BIG UP MAN!!!!!!!

– LuckyBlue
Jan 1 at 5:42

You will also want to delete the copy constructor and assignment operator.

– user4581301
Jan 1 at 5:44

|
show 1 more comment

you can do it like -

#include <iostream>



using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};

    static PersonA* p;

    public:

    static PersonA* createInstance(){

        if(p == nullptr)

        {

            cout << "Instance created" << endl;

            p= new PersonA();

        }

        return p;

    };

};



PersonA* PersonA::p=nullptr;



int main()

{

    PersonA* A = PersonA::createInstance();

    PersonA* B = PersonA::createInstance();

    return 0;

}

answered Jan 1 at 5:29

user1438832

39318

you can do it like -

#include <iostream>



using namespace std;



class PersonA{

    private:

    PersonA(){cout << "PersonA cconstr called" << endl;};

    static PersonA* p;

    public:

    static PersonA* createInstance(){

        if(p == nullptr)

        {

            cout << "Instance created" << endl;

            p= new PersonA();

        }

        return p;

    };

};



PersonA* PersonA::p=nullptr;



int main()

{

    PersonA* A = PersonA::createInstance();

    PersonA* B = PersonA::createInstance();

    return 0;

}

answered Jan 1 at 5:29

user1438832

39318

answered Jan 1 at 5:29

user1438832

39318

answered Jan 1 at 5:29

user1438832

39318

answered Jan 1 at 5:29

user1438832

39318

Thank you thank you, god bless. Happy new year

– LuckyBlue
Jan 1 at 5:31

Attempting to code when drunk is not good

– LuckyBlue
Jan 1 at 5:31

But happy new year anyway!!

– LuckyBlue
Jan 1 at 5:31

BIG UP MAN!!!!!!!

– LuckyBlue
Jan 1 at 5:42

You will also want to delete the copy constructor and assignment operator.

– user4581301
Jan 1 at 5:44

|
show 1 more comment

Thank you thank you, god bless. Happy new year

– LuckyBlue
Jan 1 at 5:31

Attempting to code when drunk is not good

– LuckyBlue
Jan 1 at 5:31

But happy new year anyway!!

– LuckyBlue
Jan 1 at 5:31

BIG UP MAN!!!!!!!

– LuckyBlue
Jan 1 at 5:42

You will also want to delete the copy constructor and assignment operator.

– user4581301
Jan 1 at 5:44

Thank you thank you, god bless. Happy new year

– LuckyBlue
Jan 1 at 5:31

Attempting to code when drunk is not good

– LuckyBlue
Jan 1 at 5:31

But happy new year anyway!!

– LuckyBlue
Jan 1 at 5:31

BIG UP MAN!!!!!!!

– LuckyBlue
Jan 1 at 5:42

You will also want to delete the copy constructor and assignment operator.

– user4581301
Jan 1 at 5:44

|
show 1 more comment

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