CODEWITHSUNDEEP
c++functionconstructormember
jabk
jabk

Reputation: 1458

Should I call a member function in a constructor

I know it's a rather a simple question and also depends on the rest of the code, but I'm more interested in the rule of thumb.

So in what cases it's appropriate to call a function inside a constructor?

What is preferable:

ClassA obj1;
obj1.memFun();

or 

ClassA obj1;
//where constructor of ClassA is
ClassA::ClassA(){ memFun(); }

Upvotes: 5

Views: 9991

Answers (5)

ahj
ahj

Reputation: 795

Conceptually it might not be the best to call a public member functions in the constructor as it implies that the constructor is doing more than initialization and creation of the object. However, having the private member functions should be fine as they are not part of the interface of the class and can be considered as helper functions to the constructor.

Upvotes: 1

fhsilva
fhsilva

Reputation: 1257

In case memFun is virtual and you do need to call it for your object to be completely built, consider using a factory method. Something like:

static ClassA* makeX(){
    ClassA* pObj = new ClassX(); // ClassX is a subclass of ClassA.
    pObj->memFun();
    return pObj ;
}

Then make ClassA and ClassX constructors protected.

Upvotes: 2

Laura Maftei
Laura Maftei

Reputation: 1863

It is usually safe to call any member function from within a constructor because the object has been completely set up prior to the execution of the first line of user code. However, it is potentially unsafe for a member function to call a virtual member function for an abstract base class during construction or destruction.

http://msdn.microsoft.com/en-us/library/s8e39b8h.aspx

Upvotes: 2

nvoigt
nvoigt

Reputation: 77285

A constructors task is to create an object in a valid, usable state. So if your function call is needed for the object's instance to be valid, please call it in the constructor.

Do not call virtual methods in your constructor though, it can lead to problems.

Upvotes: 4

Dr. Debasish Jana
Dr. Debasish Jana

Reputation: 7118

It's no harm to call a member function within your constructor. However, make sure the member function is non-virtual one, as dynamic binding mechanism starts after constructor is done. If memFun is virtual and overridden in its subclass, then calling memFun will bind to ClassA::memFun

Upvotes: 13

Related Questions