Custom manipulator for class

Question

I\'m trying to write a stream manipulator with arguments. I have class with 3 int\'s CDate(Year, Month, Day). So I need to make manipulator date_format(const char*)

Answer 1

You can use pword array for this. Every iostream in C++ has two arrays associated with it.

ios_base::iword - array of ints
ios_base::pword - array of void* pointers

You can store you own data in it. To obtain an index, that refers to an empty element in all iword and pword arrays you should use function std::ios_base::xalloc(). It returns int that you can use as an unique index in *word. You should obtain that index once on the start-up, and than use it for all operations with *word.

Then programming your own manip will look like:

Manipulator function, that receives reference to ios_base object and pointer to the format string, simply stores that pointer in pword

iosObject.pword(index_from_xalloc) = formatString

Then overloaded operator << (>>) obtains format string from the iostream object in the same way. After that you just make a conversion referencing to the format.