Re: Exception base class

From:
"AnonMail2005@gmail.com" <anonmail2005@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Wed, 10 Mar 2010 13:10:58 CST
Message-ID:
<3513d21d-7ce3-4f5c-a1a6-9c6ba5869d28@e7g2000yqf.googlegroups.com>
On Mar 10, 10:46 am, Lars Schouw <schou...@yahoo.com> wrote:

Hi,

I want to construct an exception base class that is easy to use.
Ideally I want to be able to throw exceptions in one liners like this:
throw Exception("string1" + "string2 <number>", 5.0);

I can use boost::format but don't want to use any boost in my code.
Would look like this.. a two liner.
string err = str( boost::format("test %s%") % "some more into");
throw Exception("string1" + "string2 <number>", 5.0);

I came up with this approach but it is not ideal.

Exception class:

class Base : public std::exception
{
public:
        Base(const std::string& whatStr) : m_whatStr(whatStr) {}
     virtual const char* what() const throw() { return
m_whatStr.c_str(); }
     virtual ~Base() throw () {}
private:
        std::string m_whatStr;

};

class TypeException : public Base
{
public:
        TypeException(std::stringstream& ss) : Base1(std::string("Type
exception: " + ss.str())) {}

};

usage:
        try
        {
                int i = 5;
                double d = 10.;
                std::stringstream ss;
                ss << "test" << " some more into " << i << " " << d;
                throw TypeException(ss);

                throw TypeException("test" << " some more into " << i << " " << d);
        }
        catch(Base1 base)
        {
                std::cout << base.what() << std::endl;
        }

Lars


My advice is twofold:

1. Build a very simple exception class that derives from
std::exception. Deriving make it easier on whatever code catches.

2. Have a separate class (or other mechanism) to build messages. See
my sample code on a message building class here:

http://groups.google.com/group/comp.lang.c++/tree/browse_frm/thread/13561b03dc61003b/fc17da60e4e721bf?rnum=11&_done=%2Fgroup%2Fcomp.lang.c%2B%2B%2Fbrowse_frm%2Fthread%2F13561b03dc61003b%2Fb1bdbd05945439f5%3F#doc_b1bdbd05945439f5

HTH

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