Making template class get another class as <T> and consider it as data type (C++)
I suppose to do some unusual stuff. I have a class template:
template<class T> class CFile
I want to build another class which would have a member of int type,
class foo
{
private:
int memb;
}
when I pass the "foo" class as "< T >" to "CFile", foo
is supposed to simply act as integer. I need ideas how to implement it only with internal logic in foo
, without changing CFile
(CFile is not allowed to contain any logic which extracts the int member from the class).
It's for a task in college, so I should not change the rules given to me. It should look like this:
class foo
{
int memb;
}
int main()
{
foo myFoo;
// The ctor of CFile takes a file path and opens the file. After that it can write
// members from type 开发者_JS百科< T > to the file. I need the CFile to write the memb member to
// the file (Remember that the CFile is passed as < T >
CFile<foo> file("c:\\file.txt");
}
Thanks.
What I think you're trying to do is for class foo
to act as an integer. For this effect you need to provide:
- A constructor that can create a
foo
from anint
. - An overloaded cast operator that implicitly casts your
foo
class to anint
.
You would have something like this:
class foo {
public:
foo() {} // Create a foo without initializing it
foo(const int &memb): _memb(memb) {} // Create and initialize a foo
operator int&() {return _memb;} // If foo is not constant
operator const int&() const {return _memb;} // If foo is constant
private:
int _memb;
};
If CFile uses streams to write to the file then you only need to implement operator<< in the Foo class.
Something like:
ofstream file;
file.open("file.txt"); //open a file
file<<T; //write to it
file.close(); //close it
in the CFile and this added to Foo:
ofstream &operator<<(ofstream &stream, Foo& foo)
{
stream << foo.memb;
return stream;
}
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