c++ factory pattern syntax

Question

In this question, the accepted answer uses the following syntax:

typedef std::map<std::string, Base*(*)()> map_type;

Can someone explain what the (*) means, I've never seen it before?

score 5 · Accepted Answer · answered Oct 16 '14 at 09:31

5

It is a function pointer that returns a Base pointer and takes no arguments, e.g.

struct Base {};

Base* myfun() {
    return 0;
}

int main() {
    std::map<std::string, Base*(*)()> mymap;
    mymap.insert(std::make_pair("hello", myfun));
}

Example

answered Oct 16 '14 at 09:31

Marco A.

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Thanks. I get that the return type is a Base*, what exactly is the (*) meant to signify? – stack user Oct 16 '14 at 09:35
1

@stackuser It's a function pointer without a name. Take a look at the linked wiki page. – Jiří Pospíšil Oct 16 '14 at 09:36
1

@stackuser That it is a pointer, a function pointer to be precise. The parenthesis are part of the syntax for specifying a function pointer. There's no name as Jiri hinted since it is not needed. – Marco A. Oct 16 '14 at 09:38
1

can we add a name, for readability? std::map mymap; – vincentB Oct 16 '14 at 09:38
@vincentB not in this case since it's a template argument – Marco A. Oct 16 '14 at 10:11

c++ factory pattern syntax

1 Answers1