Question

Actually my question is all in the title.
Anyway:
I have a class and I use explicit constructor:
.h

class MyClass {   public:     explicit MyClass(const string& s): query(s) {}   private:    string query; } 

Is it obligatory or not to put explicit keyword in implementation(.cpp) file?

Answer 1

No, it is not. The explicit keyword is only permitted in the header. My gcc says:

test.cpp:6: error: only declarations of constructors can be 'explicit' 

for the following code:

class foo { public:     explicit foo(int); };  explicit foo::foo(int) {}