Function pointer to singleton class instance function

Question

What I'm trying to do is create a function pointer to a single class instance function. I want to do this so I can do something like this:

C->member_method();

instead of:

Config::inst()->member_method();

but I'm not sure how to go about it. Here is my singleton class:

class Config {
private:
    Config() {}

    static Config* m_instance;

public:
    ~Config() {}

    static Config* inst() {
        if (m_instance == nullptr) {
            m_instance = new Config;
        }
        return m_instance;
    }

    bool load();
};

Thanks in advance

You mean just `member_method()`? What's wrong with `Config::instance()->load()`? That's kind of how singletons work. — Barry, Jun 14 '15 at 20:13
Looks like you simply want to create a global variable. You don't even need a pointer. You can just declare `Config C;` at the global scope and be using `C.member_method();`. But it doesn't seem like a terribly good idea. — The Paramagnetic Croissant, Jun 14 '15 at 20:14
I was thinking about going the singleton route because I need a global class which contains variables loaded in from a configuration file. From what I've read, there are advantages of using a singleton instead of something like a static object. However, I don't want to call the singleton's methods like `Config::inst()->method_name()` throughout all of my code cus lazy. I guess if there's not a way to do this, I'll just use a static object — th3v0id, Jun 14 '15 at 20:21
Once you go the singleton way there is no coming back. Your avatar confirm your allegiance to the dark side. — UmNyobe, Jun 14 '15 at 20:23
That class doesnt have to be a singleton. Create a normal class with non static method, create a static instance of the class and voila — UmNyobe, Jun 14 '15 at 20:25
@UmNyobe Doesn't necessarily have to be a `static` instance. — πάντα ῥεῖ, Jun 14 '15 at 20:32

score 1 · Answer 1 · answered Jun 14 '15 at 20:19

Use a static class method for a facade, to let you use your preferred syntax:

class Config {

    // The declarations you already have, then:

public:

    static void member_method()
    {
        inst()->member_method_impl();
    }
private:
    void member_method_impl();
};

Then, simply invoke:

Config::member_method();

If you just want to use a class pointer-like syntax, you don't need to declare anything. Just use:

auto C=Config::inst();

then:

C->member_method();

score 1 · Accepted Answer · edited May 23 '17 at 10:26

1

Simply create a normal class without static methods, ditch the singleton pattern aside, and create an instance.

The burden of singleton pattern usually outweigh any benefit.

edited May 23 '17 at 10:26

Community

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answered Jun 14 '15 at 20:31

UmNyobe

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I think im going to follow your advice. I don't fully understand the singleton pattern and what I need is fairly straight forward / simple. – th3v0id Jun 14 '15 at 20:36

Function pointer to singleton class instance function

2 Answers2