Initializing a reference to member to NULL in C++

Question

Is it possible to initialize a reference member to NULL in c++?
I'm trying to something like this:

class BigClass { private:   Object m_inner; public:   const Object& ReadOnly;   BigClass() : ReadOnly(NULL)   {     Do stuff.   } }; 

I know I can do this if I initialize "ReadOnly" to a real reference of an object, but when I want to put in there "NULL", i get the error:

"cannot convert from 'int' to 'const Object &'

How can I solve this?

Answer 1

No, references cannot be NULL in C++.¹

Possible solutions include:

• using a pointer instead of a reference.
• having a dummy Object instance that can be used to indicate "no object".

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_{[1] From the C++11 standard:}

_{[dcl.ref] [...] a null reference cannot exist in a well-defined program, because the only way to create such a reference would be to bind it to the “object” obtained by dereferencing a null pointer, which causes undefined behavior.}