Why the singleton initialization failed (link error)

Asked Sep 20 '17 at 15:31

Active Sep 20 '17 at 15:31

Viewed 29 times

I have defined a singleton as below:

struct Conditions {
    bool bMonolithic;
    bool bKeepVersion;
    bool bToc;

    static Conditions& initialize() {
        if (instance == nullptr)
            instance = new Conditions;
        return *instance;
    }
private: 
    Conditions():bMonolithic(false), bKeepVersion(false), bToc(false) {}
    static Conditions* instance;
};

When I try to use it, I call the initialize() function:

Conditions& kcondition = Conditions::initialize();

However, the compiler gives me this error:

error LNK2001: unresolved external symbol "private: static struct Conditions * Conditions::instance" (?instance@Conditions@@0PEAU1@EA)

What is the correct way to use the singleton?

asked Sep 20 '17 at 15:31

lightrek

2

And do you have an instance of it in a c++ file? – UKMonkey Sep 20 '17 at 15:32
4

I recommend you consider this design for your singleton. https://stackoverflow.com/questions/1008019/c-singleton-design-pattern/1008289#1008289 – Galik Sep 20 '17 at 15:33
Seconded. Your code is not a good C++ implementation for a singleton. – spectras Sep 20 '17 at 15:36
@UKMonkey yes, this line `Conditions& kcondition = Conditions::initialize();` – lightrek Sep 20 '17 at 15:40
2

No, UKMonkey meant where is `Conditions* Conditions::instance;`? – StoryTeller - Unslander Monica Sep 20 '17 at 15:43
@StoryTeller yes, you are right, I didn't define that static member. – lightrek Sep 20 '17 at 16:06

Why the singleton initialization failed (link error)

0 Answers0