Database: Set dir as #define

[jzych]

"../databse.txt" can be set ad #define, because this value is constant for whole project and used more then once.

UniversityDatabase/Database.hpp

Lines 39 to 40 in 3aeff1f

	bool loadFromFile(const std::string filename = "../database.txt");
	bool saveToFile(const std::string filename = "../database.txt");

[ziobron]

I do not recommend using #define in C++
It's better to have a constant value that keeps this information.

[gitmajo]

@jzych @LordLukin @majkel84
I had some problems / doubts with that change.
I know that there are two options to set default value to fuction parameter.

Based on below links:
https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.cbclx01/cplr239.htm
https://en.cppreference.com/w/cpp/string/basic_string/operator%22%22s
https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_73/rzarg/cplr038.htm

1. const dbfilename above Database.hpp class (global variable)
2. static member, which must be literal, so it should be rather static constexpr member

It seems to me that second version is better, because we can hide it in private section. What do you think?

Problems:
I wasn't able to avoid using auto keyword here.
I don't understand why I wasn't able to define my own string literal like that:
using namespace std::string_literals;
constexpr static std::string dbFilename = "../database.txt"s; //literal

Do you know what is wrong in that approach?

[ziobron]

You don't need to use string_literals here. I guess the problem lies in static member initialization. Try to initialize it outside class definition.
hpp: static std::string dbFilename;
cpp: std::string Database::dbFilename = "../database.txt;"
It cannot be constexpr because it would be uninitialized in a place of definition.