sqlite modern cpp wrapper

This library is a lightweight modern wrapper around sqlite C api .

#include<iostream>
#include <sqlite_modern_cpp.h>
using namespace  sqlite;
using namespace std;

int main() {

	try {
		// creates a database file 'dbfile.db' if it does not exists.
		database db("dbfile.db");

		// executes the query and creates a 'user' table
		db <<
			"create table if not exists user ("
			"   _id integer primary key autoincrement not null,"
			"   age int,"
			"   name text,"
			"   weight real"
			");";

		// inserts a new user record.
		// binds the fields to '?' .
		// note that only types allowed for bindings are :
		//      int ,long, long long, float, double
		//      string , u16string
		// sqlite3 only supports utf8 and utf16 strings, you should use std::string for utf8 and std::u16string for utf16.
		// note that u"my text" is a utf16 string literal of type char16_t * .
		db << "insert into user (age,name,weight) values (?,?,?);"
			<< 20
			<< u"bob"
			<< 83.25;

		int age = 21;
		float weight = 68.5;
		string name = "jack";
		db << u"insert into user (age,name,weight) values (?,?,?);" // utf16 query string
			<< age
			<< name
			<< weight;

		cout << "The new record got assigned id " << db.last_insert_rowid() << endl;

		// slects from user table on a condition ( age > 18 ) and executes
		// the lambda for each row returned .
		db << "select age,name,weight from user where age > ? ;"
			<< 18
			>> [&](int age, string name, double weight) {
			cout << age << ' ' << name << ' ' << weight << endl;
		};

		// selects the count(*) from user table
		// note that you can extract a single culumn single row result only to : int,long,long,float,double,string,u16string
		int count = 0;
		db << "select count(*) from user" >> count;
		cout << "cout : " << count << endl;

		// you can also extract multiple column rows
		db << "select age, name from user where _id=1;" >> tie(age, name);
		cout << "Age = " << age << ", name = " << name << endl;

		// this also works and the returned value will be automatically converted to string
		string str_count;
		db << "select count(*) from user" >> str_count;
		cout << "scount : " << str_count << endl;
	}
	catch (exception& e) {
		cout << e.what() << endl;
	}
}

Transactions

You can use transactions with begin;, commit; and rollback; commands. (don't forget to put all the semicolons at the end of each query).

		db << "begin;"; // begin a transaction ...   
		db << "insert into user (age,name,weight) values (?,?,?);"
			<< 20
			<< u"bob"
			<< 83.25f;
		db << "insert into user (age,name,weight) values (?,?,?);" // utf16 string
			<< 21
			<< u"jack"
			<< 68.5;
		db << "commit;"; // commit all the changes.
                
		db << "begin;"; // begin another transaction ....
		db << "insert into user (age,name,weight) values (?,?,?);" // utf16 string
			<< 19
			<< u"chirs"
			<< 82.7;
		db << "rollback;"; // cancel this transaction ...

Dealing with NULL values

If you have databases where some rows may be null, you can use boost::optional to retain the NULL value between C++ variables and the database. Note that you must enable the boost support by including the type extension for it.

	#include <sqlite_modern_cpp.h>
	#include <sqlite_modern_cpp/extensions/boost_optional.h>
	
	struct User {
		long long _id;
		boost::optional<int> age;
		boost::optional<string> name;
		boost::optional<real> weight;
	};
	
	{
		User user;
		user.name = "bob";
		
		// Same database as above
		database db("dbfile.db");
		
		// Here, age and weight will be inserted as NULL in the database.
		db << "insert into user (age,name,weight) values (?,?,?);"
			<< user.age
			<< user.name
			<< user.weight;
			
		user._id = db.last_insert_rowid();
	}
	
	{
		// Here, the User instance will retain the NULL value(s) from the database.
		db << "select _id,age,name,weight from user where age > ? ;"
			<< 18
			>> [&](long long id,
				boost::optional<int> age, 
				boost::optional<string> name
				boost::optional<real> weight) {
			
			User user;
			user._id = id;
			user.age = age;
			user.name = move(name);
			user.weight = weight;
			
			cout << "id=" << user._id
				<< " age = " << (user.age ? to_string(*user.age) ? string("NULL"))
				<< " name = " << (user.name ? *user.name : string("NULL"))
				<< " weight = " << (user.weight ? to_string(*user.weight) : string(NULL))
				<< endl;
		};
	}

Errors

On error, the library throws an error class indicating the type of error. The error classes are derived from the SQLITE3 error names, so if the error code is SQLITE_CONSTRAINT, the error class thrown is sqlite::exceptions::constraint. Note that all errors are derived from sqlite::sqlite_exception and that itself is derived from std::runtime_exception.

node: for NDK use the full path to your database file : sqlite::database db("/data/data/com.your.package/dbfile.db").

Building and Installing

The usual way works for installing:

./configure && make && sudo make install

Note, there's nothing to make, so you there's no need to run configure and you can simply point your compiler at the hdr/ directory.

##License

MIT license - http://www.opensource.org/licenses/mit-license.php