CODEWITHSUNDEEP
c++templatesfunctionsingleton
Kiran
Kiran

Reputation: 5526

problems with this singleton (Not class)

I am sure this could have been answered but I couldn't actually find a consolidated answer.

what are the problems with the following singleton that is just a function and guaranteed to have initialization and assuming T supports operator!, needed constructors, functions etc? (I am not looking for thread safety). More over, its ok for others to create objects of T as T in my case is a database handle I want to use for the life of my program. 

template<typename T>
T* getInstance(){
    static T instance;
    if ( !instance && !instance.initialize() ){
       return NULL;
    }
    else {
       return &instance;
    }
}

Upvotes: 1

Views: 106

Answers (2)

Nick
Nick

Reputation: 5805

There are some mistakes in your code -- the template type is being used instead of the variable.

For what you need (don't care about thread safety & need it for the entire duration of your application), it might be exactly what you need. You might wish to start from this though:

template<typename T> T* getInstance()
{
    static T instance;
    return &instance;
}

Upvotes: 1

Daniel Lidstr&#246;m
Daniel Lidstr&#246;m

Reputation: 10280

This won't even compile. Moreover, using singletons will get you in trouble sooner or later. For instance, when will you destroy the instance? In C++ it is generally better to be explicit about construction and destruction. Lookup the static gateway pattern (example in C#).

Good luck!

Upvotes: 0

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