Re: Globals

From:

Victor Bazarov <v.bazarov@comcast.invalid>

Newsgroups:

comp.lang.c++

Date:

Fri, 05 Nov 2010 10:56:35 -0400

Message-ID:

<ib15v4$m86$1@news.eternal-september.org>

On 11/5/2010 10:48 AM, Andrea Crotti wrote:

Andrea Crotti<andrea.crotti.0@gmail.com> writes:

Again on the "Globals" problem.
Since I also have an option parser, to avoid repetition and other
annonying things this approach

namespace GLOBALS
{
     int num_landmarks;
     int trace_length;
     int history_size;
     int distribution_size;
     Environment *environment;
     ostream *out;

is no longer good.
I need a class which stores a map where for example I keep a mapping
like

conf["num_landmarks"] = 3;
and so on.

So how do I make a class for only one object without using the annoying
singleton.
I actually don't care that it could be called more times (which won't).

Should I define the class (as extern??) in the header file and in the
.cpp allocate an object of it?

Ok I thought something like
--8<---------------cut here---------------start------------->8---
class Globals
{
private:
     std::map<string, string> config;

public:
     Globals();
     string operator[](string& idx) { return config[idx]; }

string& operator[](string const& idx) { return config[idx]; }

(returns a reference and takes a reference to const).

};

extern Globals CONFIG;

Why do you really need a class? Why can't you simply do

extern std::map<std::string,std::string> GLOBALS;

?

--8<---------------cut here---------------end--------------->8---

in the header would work, but the operator[] doesn't work as I thought.
How do I pass a reference to a string to it?
I would like to be able to do

CONFIG["variable"] = 10;

for example, but I guess that's not casted to string reference in C++...

V
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