OTL 4.0, Example 100 (otl_value<T> / otl_compact_value<T,null> / std::optional<T>, DB2-CLI)

This example demonstrates OTL streams and otl_value<T> / otl_compact_value<T,null> / std::optional<T>.

Source Code

#include <iostream>
#include <string>
#define OTL_DB2_CLI // Compile OTL 4.0/DB2-CLI
#define OTL_STL // Turn on STL features and otl_value<T>
#define OTL_ANSI_CPP // Turn on ANSI C++ typecasts

#if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON)
// enable OTL support for std::optional when clang or g++ is used and
// when -std=c++14 or higher switch is used
#define OTL_STREAM_WITH_STD_OPTIONAL_ON
#endif

#if defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
#define OTL_STREAM_WITH_STD_OPTIONAL_ON
#endif

#include <otlv4.h> // include the OTL 4.0 header file
#if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON) \
&& defined(OTL_STREAM_WITH_STD_OPTIONAL_ON)
// for clang or g++, when they use -std=c++14 or higher
#include <experimental/optional>
#endif

#if defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
#include <optional>
#endif
using namespace std; otl_connect db; // connect object void insert() // insert rows into table { otl_stream o(50, // buffer size "insert into test_tab " "values(:f1<int>,:f2<char[31]>,:f3<db2date>)", // SQL statement db // connect object ); otl_compact_value<int,-1> f1; // otl_compact_value container for int, and -1 as NULL value otl_value<string> f2; // otl_value container of STL string #if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON) \
&& defined(OTL_STREAM_WITH_STD_OPTIONAL_ON)
// for clang or g++, when they use -std=c++14 or higher
std::experimental::optional<otl_datetime> f3; // container of otl_datetime
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
std::optional<otl_datetime> f3; // container of otl_datetime
#else
otl_value<otl_datetime> f3; // container of otl_datetime #endif
for(int i=1;i<=100;++i){ f1=i; if(i%2==0) f2="NameXXX"; else f2=otl_null(); // Assign otl_null() to f2 if(i%3==0){ #if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON) \
&& defined(OTL_STREAM_WITH_STD_OPTIONAL_ON)
// for clang or g++, when they use -std=c++14 or higher
f3.emplace(otl_datetime());
f3->year=2001;
f3->month=1;
f3->day=1;
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
f3.emplace(otl_datetime());
f3->year=2001;
f3->month=1;
f3->day=1;
#else
// Assign a value to f3 via the .v field directly
f3.v.year=2001;
f3.v.month=1;
f3.v.day=1;
f3.set_non_null(); // Set f3 as a "non-NULL"
#endif
}else
#if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON) \
&& defined(OTL_STREAM_WITH_STD_OPTIONAL_ON)
// for clang or g++, when they use -std=c++14 or higher
f3=std::experimental::optional<otl_datetime>();
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
f3=std::optional<otl_datetime>();
#else
f3.set_null(); // Set f3 as null via .set_null() function
#endif
#if defined(OTL_ANSI_CPP_11_VARIADIC_TEMPLATES)
otl_write_row(o,f1,f2,f3);
#else
// when variadic template functions are not supported by the C++
// compiler, OTL provides nonvariadic versions of the same template
// functions in the range of [1..15] parameters
otl_write_row(o,f1,f2,f3);

// the old way (operators >>() / <<()) is available as always:
// o<<f1<<f2<<f3; #endif
} } void select() { otl_stream i(50, // buffer size "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2", // SELECT statement db // connect object ); // create select stream otl_compact_value<int,-1> f1(0); otl_value<string> f2; #if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON) \
&& defined(OTL_STREAM_WITH_STD_OPTIONAL_ON)
// for clang or g++, when they use -std=c++14 or higher
std::experimental::optional<otl_datetime> f3;
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
std::optional<otl_datetime> f3;
#else
otl_value<otl_datetime> f3; #endif
#if defined(OTL_ANSI_CPP_11_VARIADIC_TEMPLATES)
otl_write_row(i,8,8);
#else
// when variadic template functions are not supported by the C++
// compiler, OTL provides nonvariadic versions of the same template
// functions in the range of [1..15] parameters
otl_write_row(i,8,8);

// the old way (operators >>() / <<()) is available as always:
// i<<8<<8; // assigning :f11, :f12 = 8 #endif
// SELECT automatically executes when all input variables are // assigned. First portion of output rows is fetched to the buffer while(!i.eof()){ // while not end-of-data #if defined(OTL_ANSI_CPP_11_VARIADIC_TEMPLATES)
otl_read_row(i,f1,f2,f3);
#else
// when variadic template functions are not supported by the C++
// compiler, OTL provides nonvariadic versions of the same template
// functions in the range of [1..15] parameters
otl_read_row(i,f1,f2,f3);

// the old way (operators >>() / <<()) is available as always:
// i>>f1>>f2>>f3; #endif
#if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON) \
&& defined(OTL_STREAM_WITH_STD_OPTIONAL_ON)
// for clang or g++, when they use -std=c++14 or higher
if(f3)
cout<<"f1="<<f1<<", f2="<<f2<<", f3="<<*f3<<endl;
else
cout<<"f1="<<f1<<", f2="<<f2<<", f3=NULL"<<endl;
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
if(f3)
cout<<"f1="<<f1<<", f2="<<f2<<", f3="<<*f3<<endl;
else
cout<<"f1="<<f1<<", f2="<<f2<<", f3=NULL"<<endl;
#else
cout<<"f1="<<f1<<", f2="<<f2<<", f3="<<f3<<endl;
#endif
} i<<4<<4; // assigning :f11, :f12 = 4 // SELECT automatically executes when all input variables are // assigned. First portion of output rows is fetched to the buffer while(!i.eof()){ // while not end-of-data i>>f1>>f2>>f3; #if (defined(__clang__) || defined(__GNUC__)) && defined(OTL_CPP_14_ON) \
&& defined(OTL_STREAM_WITH_STD_OPTIONAL_ON)
// for clang or g++, when they use -std=c++14 or higher
if(f3)
cout<<"f1="<<f1<<", f2="<<f2<<", f3="<<*f3<<endl;
else
cout<<"f1="<<f1<<", f2="<<f2<<", f3=NULL"<<endl;
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
if(f3)
cout<<"f1="<<f1<<", f2="<<f2<<", f3="<<*f3<<endl;
else
cout<<"f1="<<f1<<", f2="<<f2<<", f3=NULL"<<endl;
#else
cout<<"f1="<<f1<<", f2="<<f2<<", f3="<<f3<<endl;
#endif
} } int main() { otl_connect::otl_initialize(); // initialize DB2-CLI environment try{ db.rlogon("scott/tiger@db2sql"); // connect to DB2 otl_cursor::direct_exec ( db, "drop table test_tab", otl_exception::disabled // disable OTL exceptions ); // drop table otl_cursor::direct_exec ( db, "create table test_tab(f1 int, f2 varchar(30), f3 date)" ); // create table insert(); // insert records into table select(); // select records from table } catch(otl_exception& p){ // intercept OTL exceptions cerr<<p.msg<<endl; // print out error message cerr<<p.stm_text<<endl; // print out SQL that caused the error cerr<<p.sqlstate<<endl; // print out SQLSTATE message cerr<<p.var_info<<endl; // print out the variable that caused the error } db.logoff(); // disconnect from DB2 return 0; }

Output

f1=8, f2=NameXXX, f3=NULL
f1=9, f2=NULL, f3=1/1/2001 0:0:0
f1=10, f2=NameXXX, f3=NULL
f1=11, f2=NULL, f3=NULL
f1=12, f2=NameXXX, f3=1/1/2001 0:0:0
f1=13, f2=NULL, f3=NULL
f1=14, f2=NameXXX, f3=NULL
f1=15, f2=NULL, f3=1/1/2001 0:0:0
f1=16, f2=NameXXX, f3=NULL
f1=4, f2=NameXXX, f3=NULL
f1=5, f2=NULL, f3=NULL
f1=6, f2=NameXXX, f3=1/1/2001 0:0:0
f1=7, f2=NULL, f3=NULL
f1=8, f2=NameXXX, f3=NULL


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Copyright 1996-2017, Sergei Kuchin, email: skuchin@gmail.com, skuchin@gmail.com.

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