Pointer to a logger class provide for all other classes?

Question

I have a Logger class in my C++ application. This class has public methods like writeDebug(std::string & str) , can write to a debug output file and it works for me very good. The object is being created on application start by the first main class and there it is stored as a Logger * myLogger; object.

Since I have other classes as well, I would like to provide this logging functionality to those classes as well.

Currently I oberhead the myLogger pointer to toher classes in their contructor, and all the other classes store this very same Logger pointer when being created --> all other classes has this Logger * myLogger pointer stored:

Other_XY_Class::Other_XY_Class(Logger * logger, ...) 
: localLoggerPtr{logger} { //.. }

==> localLoggerPtr (in class Other_XY_Class) == myLogger (in main application class)

I can imagine that there is a more convenient / elegant way to handle that ?

I would use a [`std::shared_ptr`](http://en.cppreference.com/w/cpp/memory/shared_ptr) if you want one instance shared among many objects. — NathanOliver, Aug 20 '15 at 12:38
Are you asking wheter using a *singleton* or a global variable is a better solution, for example? — Paolo M, Aug 20 '15 at 12:41
I think what you do is called dependency injection and it is good. — trenki, Aug 20 '15 at 12:45
@prajmus: I don't think making it static is good. That basically makes it a singleton. Why should I only want one logger? Maybe I want to have two different one to log to different files? — trenki, Aug 20 '15 at 12:47
@trenki ok, I get the use case, but I just thought OP wants to have only one object, but doesn't want to share the pointer between classes. — prajmus, Aug 20 '15 at 12:51
@trenki `Why should I only want one logger?` Because if you don't need more, then it's simpler. That said, I wouldn't make the memeber function static either. Instead, I'd use a global instance because that's just as simple and doesn't limit you to just one logger. — eerorika, Aug 20 '15 at 12:51

score 0 · Answer 1 · answered Aug 20 '15 at 12:46

0

Since you only have one instance, why not use a Singleton for that?

Something along this lines:

class foo {
private:
   void bar();

   static foo Instance;

public:
  static void Bar() { Instance.bar(); }
}

answered Aug 20 '15 at 12:46

MHolzmayr

1,541
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What's the advantage of this as opposed to just making `bar` static? – eerorika Aug 20 '15 at 12:47
1

This is hardly a singleton... – SingerOfTheFall Aug 20 '15 at 13:06
In my Logging class I have already created a private file handle File* file which I use oneach write attempt. How would I access that? – MarkZltr Aug 20 '15 at 13:27
I like the idea of a singleton, but new problem: http://stackoverflow.com/questions/32120691/singleton-with-two-getinstance-methods-handing-over-a-parent-pointer – MarkZltr Aug 20 '15 at 14:17

Pointer to a logger class provide for all other classes?

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