Integrating an ARX application with SQLite

<?xml encoding=”UTF-8″>By Sreeparna Mandal

A brief introduction to SQLite:

SQLite is a C-language library that implements a small, fast, self-contained, high-reliability, full-featured SQL database engine. For programs that have a lot of data that must be sifted and sorted in diverse ways, it is often easier and quicker to load the data into an in-memory SQLite database and use queries with joins and ORDER BY clauses to extract the data in the form and order needed.

What can an ARX Application integrated with SQLite do?

The ARX application can create a new database and add tables to it by defining the structure of each table and adding data to it through INSERT statements. If a database containing tables already exists, the ARX can fetch the necessary data from it using SELECT statements combined with other clauses, store the records in a data structure and use it to create a drawing in AutoCAD.

How to create an ARX Application integrated with SQLite?

Step 1:

Download the C source code of SQLite as an amalgamation from its website.

Step 2:

Create a new project with “ARX/DBX Project for AutoCAD” template. Add shell.c and sqlite3.c to Source Files in the project.

Step 3:

Set Project->Properties->C/C++->Code Generation->Smaller Type Check to No

Step 4:

Set Properties->C/C++->Pre Compiled Header->Pre Compiled Header to NOT USING

Step 5:

To create a table by adding it to a database:

1. Define the table structure(s) as members of the class.

   <span>
   struct LineCoord
   {
   int x_coord;
   int y_coord;
   };
   </span>

2. Open the particular database using sqlite3_open() function.

   <span>
   sqlite3* db;
   if (sqlite3_open("LineCoordDB.db", &db) != SQLITE_OK)
   {
   sqlite3_close(db);
   return;
   }
   </span>

3. Store the CREATE TABLE query as a string. Prepare the sql query from this string using sqlite3_prepare() and execute this query using sqlite3_step().

   <span>
   std::string createTableQuery = "CREATE TABLE LINECOORD ("
   "ID INT PRIMARY KEY NOT NULL,"
   "XCOORD INT NOT NULL,"
   "YCOORD INT NOT NULL);";
   //prepare sql statement from the string containing the query
   sqlite3_stmt* createTableStmt;
   sqlite3_prepare(db, createTableQuery.c_str(), static_cast(createTableQuery.size()), &createTableStmt, nullptr);
   //execute sql query to create table
   if (sqlite3_step(createTableStmt) != SQLITE_DONE)
   {
   sqlite3_close(db);
   }
   </span>

Step 6:

Inserting data into table:

1. Store the INSERT query into a string or in case of multiple INSERT statements, use a vector of string.

   <span>
   std::vector insertStmtList;
   insertStmtList.emplace_back("INSERT INTO LINECOORD ('ID', 'XCOORD', 'YCOORD') VALUES ('101', '1', '1');");
   </span>

2. Prepare the sql query from the string using sqlite3_prepare() and execute this query using sqlite3_step().

   <span>
   for (const auto& insertQueryStr : insertStmtList)
   {
   sqlite3_stmt* insertStmt;
   sqlite3_prepare(db, insertQueryStr.c_str(), static_cast(insertQueryStr.size()), &insertStmt, nullptr);
   //execute each sql stmt
   if (sqlite3_step(insertStmt) != SQLITE_DONE)
   {
   sqlite3_close(db);
   return;
   }
   }
   </span>

3. Close the database using sqlite3_close().

The created table and its data can be checked by installing ‘DB Browser (SQLite)’ from official website of SQLite.

Step 7:

To fetch data from an existing table

1. Open the particular database using sqlite3_open() function.
2. Define the following where each variable of Record type will hold data of a tuple(row) and a variable of Records type will hold the data of the entire table:

   <span>
   using Record = std::vector;
   using Records = std::vector;
   </span>

3. We call a user defined function with string parameter containing the sql SELECT query to fetch all the data and return it to a variable of Records type. Inside the user defined function, we use a callback. SQLite will call this callback function for each record processed in each SELECT statement executed within the SQL argument.

For a very basic understanding, you may refer to the example shown in SQLite website. Kindly refer to the methods ADSKMyGroupGetLineCoord(), select_callback() and exec_select_stmt() from the complete source code to see the full implementation.

Step 8:

To create a drawing using the data stored in the table

In this case, extract data of each record(an X-coordinate and a Y-coordinate) from the data structure used to store the table values and use them to draw a line.

Complete sample with source code is available at Github : Arx_SQLite_2DLineCoordinates