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Tip of the Day
Language: C++
Expertise: Beginner
Sep 18, 2000

Checking If a Function Pointer is Valid

Question:
I am collecting a number of function pointers in C++ and before I call them I want to check to see if they have been set. I really want to avoid calling them if they aren't valid. I have tried the following "if func != Null { ... " but I get an error.

Answer:
First of all, there's no 'Null' in C++. The constant NULL is all uppercase. However, it's not a keyword so you have to #include a header file to make its definition visible to the compiler. The best way check for nullness is to compare the pointer (any type of pointer, including a pointer to member) to the literal zero:

if (pmf!=0)
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