README

Dependency Injection Container Demo

A Free Pascal implementation of a dependency injection container with different service lifetimes (Singleton, Transient, Scoped).

Project Structure

DIContainerdemo/
????????? src/                          # Source code
???   ????????? AppContainer.pas          # Main DI container implementation
???   ????????? LoggerIntf.pas           # Logger interface
???   ????????? Loggers.pas              # Basic logger implementations
???   ????????? EnhancedLoggers.pas      # Advanced loggers with lifetime demos
???   ????????? CalculationService.pas   # Example service implementation
???   ????????? Demo.pas                 # Basic demo program
???   ????????? TestLifetimeFeatures.pas # Lifetime testing program
???   ????????? ContainerLifetimeTests.pas # Test framework
???   ????????? LifetimeDemo.pas         # Advanced lifetime examples
???   ????????? WebAppLifetimeDemo.pas   # Web application simulation
???   ????????? CalculationService_FakeLoggerTest.pas # Unit test example
????????? build/                       # Compiled output (executables, .ppu, .o files)
????????? docs/                        # Documentation
???   ????????? ContainerPatternGuide.md # Detailed pattern guide
????????? .vscode/                     # VS Code configuration
????????? README.md                    # This file

Building the Project

Using VS Code Tasks (Recommended)

Press Ctrl+Shift+P and type "Tasks: Run Task" then select:

• Compile Demo (Enhanced Debug) - Builds the main demo with full debug info
• Compile TestLifetimeFeatures (Debug) - Builds the test suite
• Compile All Programs - Builds all programs at once
• Clean Build Files - Cleans the build directory
• Run Demo - Compiles and runs the main demo
• Run Tests - Compiles and runs the test suite

Using Command Line

# Compile main demo
fpc src/Demo.pas -FUbuild -FEbuild -g -gl

# Compile test suite  
fpc src/TestLifetimeFeatures.pas -FUbuild -FEbuild -g -gl

# Run programs
./build/Demo
./build/TestLifetimeFeatures

# Clean build files
rm -rf build/*

Programs

• Demo - Basic dependency injection demonstration
• TestLifetimeFeatures - Comprehensive lifetime management tests

Features

• Singleton Lifetime - One instance for the entire application
• Transient Lifetime - New instance every time it's requested
• Scoped Lifetime - One instance per scope (e.g., per web request)
• Factory Pattern - Compatible with Free Pascal 3.2.2
• Interface-based - Clean separation of concerns
• Thread-safe - Ready for multi-threaded applications

Requirements

• Free Pascal Compiler (FPC) 3.2.2 or later
• Linux/Windows/macOS

Getting Started

1. Open the project in VS Code
2. Press Ctrl+Shift+P → "Tasks: Run Task" → "Run Demo"
3. Check the output to see dependency injection in action
4. Run "Run Tests" to see all lifetime behaviors tested

Documentation

See docs/ContainerPatternGuide.md for detailed explanations of the dependency injection patterns implemented in this project.