| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"TBass" |
| Date: |
18 Dec 2007 07:40:03 AM |
| Object: |
Put numbers in std::string |
Hi,
I've been switching a C program over to C++, and using std::string for
all the string members of the class.
One question I'm having trouble finding documentation on is how to put
numeric varaible data into a string. For example, in the C program I
did the following:
sprintf( sql, "SELECT * FROM DEVICES WHERE RKEY=\'%d\'", device_id );
But, in C++, I'm trying to do something similar to the following:
std::string sql;
int device_id;
sql = "SELECT * FROM DEVICES WHERE RKEY = ' ".... ?? HOW DO I INSERT
THE VALUE OF device_id?
I'm trying to do things the proper "C++" way.
Thanks in advance,
T
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| User: "Nick Keighley" |
|
| Title: Re: Put numbers in std::string |
18 Dec 2007 07:54:04 AM |
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On 18 Dec, 13:40, TBass <t...@automateddesign.com> wrote:
I've been switching a C program over to C++, and using std::string for
all the string members of the class.
One question I'm having trouble finding documentation on is how to put
numeric varaible data into a string. For example, in the C program I
did the following:
sprintf( sql, "SELECT * FROM DEVICES WHERE RKEY=\'%d\'", device_id );
But, in C++, I'm trying to do something similar to the following:
std::string sql;
int device_id;
sql = "SELECT * FROM DEVICES WHERE RKEY = ' ".... ?? HOW DO I INSERT
THE VALUE OF device_id?
I'm trying to do things the proper "C++" way.
#include <sstream>
std::ostringstream sql;
sql << "SELECT * FROM DEVICES WHERE RKEY=\'" << device_id << "\'";
do_sql (sql.str().c_str()); // assuming do_sql() takes a char*
that's from memory so check the documentation
--
Nick Keighley
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| User: "TBass" |
|
| Title: Re: Put numbers in std::string |
18 Dec 2007 08:29:34 AM |
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On Dec 18, 7:54 am, Nick Keighley <nick_keighley_nos...@hotmail.com>
wrote:
On 18 Dec, 13:40, TBass <t...@automateddesign.com> wrote:
I've been switching a C program over to C++, and using std::string for
all the string members of the class.
One question I'm having trouble finding documentation on is how to put
numeric varaible data into a string. For example, in the C program I
did the following:
sprintf( sql, "SELECT * FROM DEVICES WHERE RKEY=\'%d\'", device_id );
But, in C++, I'm trying to do something similar to the following:
std::string sql;
int device_id;
sql = "SELECT * FROM DEVICES WHERE RKEY = ' ".... ?? HOW DO I INSERT
THE VALUE OF device_id?
I'm trying to do things the proper "C++" way.
#include <sstream>
std::ostringstream sql;
sql << "SELECT * FROM DEVICES WHERE RKEY=\'" << device_id << "\'";
do_sql (sql.str().c_str()); // assuming do_sql() takes a char*
that's from memory so check the documentation
--
Nick Keighley- Hide quoted text -
- Show quoted text -
Thanks, guys. That's exactly what I need.
Much appreciated,
T
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| User: "Boris" |
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| Title: Re: Put numbers in std::string |
18 Dec 2007 09:45:09 AM |
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On Tue, 18 Dec 2007 15:40:03 +0200, TBass <tbj@automateddesign.com> wrot=
e:
Hi,
I've been switching a C program over to C++, and using std::string for=
all the string members of the class.
One question I'm having trouble finding documentation on is how to put=
numeric varaible data into a string. For example, in the C program I
did the following:
sprintf( sql, "SELECT * FROM DEVICES WHERE RKEY=3D\'%d\'", device_id )=
;
But, in C++, I'm trying to do something similar to the following:
std::string sql;
int device_id;
sql =3D "SELECT * FROM DEVICES WHERE RKEY =3D ' ".... ?? HOW DO I INSE=
RT
THE VALUE OF device_id?
I'm trying to do things the proper "C++" way.
If you are using Boost C++ Libraries already Boost.Format might be an =
option: http://www.boost.org/libs/format/index.html
Your code would look like this then:
std::string sql =3D boost::str(boost::format("SELECT * FROM DEVICES WHER=
E =
RKEY=3D\'%1%\'") % device_id);
Boris
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| User: "Christian Hackl" |
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| Title: Re: Put numbers in std::string |
18 Dec 2007 02:14:38 PM |
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Boris wrote:
On Tue, 18 Dec 2007 15:40:03 +0200, TBass <tbj@automateddesign.com> wrote:
sql = "SELECT * FROM DEVICES WHERE RKEY = ' ".... ?? HOW DO I INSERT
THE VALUE OF device_id?
I'm trying to do things the proper "C++" way.
If you are using Boost C++ Libraries already Boost.Format might be an
option: http://www.boost.org/libs/format/index.html
There's also boost::lexical_cast:
try
{
string sql = "SELECT * FROM DEVICES WHERE RKEY = '" +
lexical_cast<string>(device_id) + "'";
}
catch (bad_lexical_cast &)
{
// error converting device_id to string
}
(By the way, this isn't related to C++, but you may check if your DBMS
allows you to use prepared statements instead of constructing query
strings manually like this.)
--
Christian Hackl
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| User: "Tim Love" |
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| Title: Re: Put numbers in std::string |
18 Dec 2007 07:56:29 AM |
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TBass <tbj@automateddesign.com> writes:
One question I'm having trouble finding documentation on is how to put
numeric varaible data into a string.
Read about stringstream. Once you can do I/O to and from files, I/O to and from strings is very similar.
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