Thread: Trouble storing ifstream object in pair object

Hello, I am trying to store an ifstream in a pair object, but when I try to assign to pair_name.second (the ifstream object) an existing ifstream object, it fails with compiler errors hinting that the assignment operator of the ios::base type is private.

Any ideas what I can do to solve the problem?

Thanks.

Originally Posted by whiteflags

Use a reference to an ifstream instead.

The problem is, the ifstream object I'm trying to assign to pair's object is a local object of a function, and so is the pair, and I'm adding the pair to a global vector. Why does it have to be a reference?

Or, if the stream is guaranteed to exist for at least as long as the pair object, use a std::pair<whatever, ifstream *> and store a pointer to the stream.

That eliminates the need to copy the actual ifstream object around - which is not allowed, and is the cause of the compilation errors.

Originally Posted by grumpy

Or, if the stream is guaranteed to exist for at least as long as the pair object, use a std:air<whatever, ifstream *> and store a pointer to the stream.

That eliminates the need to copy the actual ifstream object around - which is not allowed, and is the cause of the compilation errors.

Well, a pointer wouldn't work either, because I would be pointing at a local ifstream object in a function which is then destroyed after the function completes its execution, thus making it impossible to use that object in other functions, which is what I hoped to do, which is why I wanted to copy the object.
So I changed my design, and am no longer trying to hold on to the ifstream objects. I instead merely store the filenames of the files associated with those ifstream objects, along with the content of each file, so I can later open those files again in other functions using completely different ifstream objects, if I need to.

You could use new along with a std::unique_ptr. Remember to use appropriate std::move.