Minimal Zig Program with C++, Qt, and SQLite Integration

This tutorial will guide you through the steps of creating a minimal Zig program that integrates with C++, Qt, and SQLite to create a simple application with a button that interacts with a local SQLite database.

Project Initialization

First, initialize your Zig project:

mkdir simple_hello
cd simple_hello
zig init

This will create a basic project structure for you.

Project Structure

Ensure your project structure looks like this:

simple_hello/
├── build.zig
├── src/
│   ├── main.zig
│   ├── main.cpp
│   ├── main.h
│   ├── database.cpp
│   └── database.h

Step 1: Create main.zig

Create the main.zig file with the following content:

const std = @import("std");

extern fn cppHelloWorld() void;
extern fn initDatabase() void;
extern fn insertData(data: [*]const u8) void;

pub fn main() void {
    // Initialize the database
    initDatabase();
    // Insert initial data
    const data = "Sample Data";
    insertData(data);

    // Call the C++ function
    cppHelloWorld();
}

Step 2: Create main.cpp

Create the main.cpp file with the following content:

#include <QApplication>
#include <QPushButton>
#include <QMessageBox>
#include <iostream>
#include <sqlite3.h>
#include "main.h"
#include "database.h"

void onButtonClick() {
    QMessageBox::information(nullptr, "Info", "Button clicked!");
}

void cppHelloWorld() {
    int argc = 0;
    char *argv[] = { nullptr };
    QApplication app(argc, argv);

    QPushButton button("Hello, World!");
    QObject::connect(&button, &QPushButton::clicked, onButtonClick);
    button.resize(200, 100);
    button.show();

    app.exec();
}

Step 3: Create main.h

Create the main.h file with the following content:

#ifndef MAIN_H
#define MAIN_H

#ifdef __cplusplus
extern "C" {
#endif

void cppHelloWorld();

#ifdef __cplusplus
}
#endif

#include "database.h"

#endif // MAIN_H

Step 4: Create database.cpp

Create the database.cpp file with the following content:

#include <iostream>
#include <sqlite3.h>
#include "database.h"

sqlite3 *db;

void initDatabase() {
    int rc = sqlite3_open("world_builder.db", &db);
    if (rc) {
        std::cerr << "Can't open database: " << sqlite3_errmsg(db) << std::endl;
        return;
    }
   char *errMsg = 0;
    const char *sql = "CREATE TABLE IF NOT EXISTS World (ID INTEGER PRIMARY KEY AUTOINCREMENT, Name TEXT NOT NULL);";
    rc = sqlite3_exec(db, sql, 0, 0, &errMsg);
    if (rc != SQLITE_OK) {
        std::cerr << "SQL error: " << errMsg << std::endl;
        sqlite3_free(errMsg);
    } else {
        std::cout << "Table created successfully" << std::endl;
    }
}

void insertData(const char *data) {
    char *errMsg = 0;
    std::string sql = "INSERT INTO World (Name) VALUES ('" + std::string(data) + "');";
    int rc = sqlite3_exec(db, sql.c_str(), 0, 0, &errMsg);
    if (rc != SQLITE_OK) {
        std::cerr << "SQL error: " << errMsg << std::endl;
        sqlite3_free(errMsg);
    } else {
        std::cout << "Data inserted successfully" << std::endl;
    }
}

Step 5: Create database.h

Create the database.h file with the following content:

#ifndef DATABASE_H
#define DATABASE_H

#ifdef __cplusplus
extern "C" {
#endif

void initDatabase();
void insertData(const char *data);

#ifdef __cplusplus
}
#endif

#endif // DATABASE_H

Step 6: Update build.zig

Update the build.zig file with the following content:

const std = @import("std");

pub fn build(b: *std.Build) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});

    const exe = b.addExecutable(.{
        .name = "simple_hello",
        .root_source_file = b.path("src/main.zig"),
        .target = target,
        .optimize = optimize,
    });

    exe.addCSourceFile(.{
        .file = b.path("src/main.cpp"),
        .flags = &[_][]const u8{
            "-I.",
            "-fPIC",
        },
    });

    exe.addCSourceFile(.{
        .file = b.path("src/database.cpp"),
        .flags = &[_][]const u8{
            "-I.",
            "-fPIC",
        },
    });

    exe.addIncludePath(b.path("src")); // Add include path for headers

    exe.linkSystemLibrary("stdc++");
    exe.linkSystemLibrary("Qt5Core");
    exe.linkSystemLibrary("Qt5Widgets");
    exe.linkSystemLibrary("sqlite3");

    b.installArtifact(exe);

    const run_cmd = b.addRunArtifact(exe);
    run_cmd.step.dependOn(b.getInstallStep());

    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);
}

Step 7: Install SQLite and Qt Development Libraries

Make sure SQLite and Qt development libraries are installed:

sudo apt-get install libsqlite3-dev qtbase5-dev

Build and Run

  1. Navigate to your project directory: 
    cd /path/to/simple_hello
  2. Build the project: 
    zig build
  3. Run the executable: 
    zig-out/bin/simple_hello

This setup should compile and run, displaying a window with a button that says "Hello, World!" and initialize an SQLite database, inserting sample data into it.