CODEWITHSUNDEEP
c#c++
user1240679
user1240679

Reputation: 6979

Using a constant variable in C++

I have a C++ file in my C++ project in Visual Studio. The C++ file has a snippet wherein some applications are run using system

system("Files\\tx1");
system("Files\\tx2");
system("Files\\tx3");
system("Files\\tx4");

I want to replace the "Files" constant with some constant variable which can be changed at a single place. Something like what we wuld do in C# with app.config files etc.
Directly hardcoding a constant is not a good practice. C++ project doesn't have settings file unlike C# projects. So, any suggestions what I should do in this case?

Upvotes: 0

Views: 224

Answers (5)

Moo-Juice
Moo-Juice

Reputation: 38810

I would create a class that did this for me:

class Path
{
private:
    static const std::string prefix_;

public:
    static std::string get(const std::string& file)
    {
        return prefix_ + '\\' + file;
    };
}; // eo class Path

.cpp

const std::string Path::prefix_ = "Files";

Now, it's easy to use everywhere else:

system(Path::get("tx1").c_str());
system(Path::get("tx2").c_str());
system(Path::get("tx3").c_str());
system(Path::get("tx4").c_str());

Upvotes: 0

CapelliC
CapelliC

Reputation: 60034

instead of a constant, place an inline function that returns values appropriate, given minimally required data: for instance

inline const char *FileNum(int n) {
 static char buf[100];
 sprintf(buf, "Files\\txt%d", n);
 return buf;
}

and call

system(FileNum(1));
...

Upvotes: -1

Constantinius
Constantinius

Reputation: 35089

If you want to use a compile time approach (as with the app.config in C#) you can use defines.

conf.h

#define FILES "mypath"

impl.c

#include "conf.h"
...

system(FILES "tx1");

When you prefer a runtime approach, there are numerous formats/libraries for configuration files.

Upvotes: 1

Mario
Mario

Reputation: 36567

You could simply write your own small settings parser which isn't that hard or use some premade library to read some kind of configuration file (e.g. you can use the Windows API to read/write ini files or you could use some kind of json/xml library).

I personally prefer using pugixml for stuff like this.

Upvotes: 0

Nick
Nick

Reputation: 25828

As there is no similar mechanism to the app.config file you will have to spin your own. There are lots of frameworks out there for doing this.

One option is to use the boost property tree library. This allows easy serialisation of configuration data to a variety of file formats.

However, you'd still have to create a global object for accessing these values.

Upvotes: 1

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