stringtrim / designpatternexamples

18 unique views of the classic Design Patterns for C, C++, C#, Python, and Rust.

Design Pattern Examples

by Stephen P. Lepisto

Copyright (c) 2023 Stephen P. Lepisto

Licensed under the MIT License. See LICENSE.md for details.

Overview

This repository contains implementations of 18 of the classic object-oriented Design Patterns as described in the book Design Patterns: Elements of Reusable Object-Oriented Software by Gamma, Helm, Johnson, and Vlissides. There are implementations in C, C++, C#, Python, and Rust. These are not implementations of the examples in the book but are my own creations to demonstrate my experience with these patterns.

The C, C++, C#, and Python examples are documented with Doxygen and the results are online at https://stephenlepisto.com/developer/designpatternexamples/.

Doxygen does not support Doxygen so the Rust example uses Rust's own documentation support, with the results also available at https://stephenlepisto.com/developer/designpatternexamples/. Refer to the Doxygen-based documentation for the overall discussion of each pattern (I didn't want to duplicate the discussions with the Rust's less capable documentation functionality).

How to Build

Minimum Requirements

These are the versions of the various applications the DesignPatternExamples were written and tested on. Later versions of these applications should continue to work.

Windows

• CMake v3.26
• Doxygen v1.9.6
• GraphViz v7.1
• Visual Studio 2022 (I used Community edition)
  • Work Loads
    • Python Development
    • .Net Desktop Development
    • Desktop Development with C++
• Python 3.11
• Rust v1.69 in release 2021
• Git Bash for Windows v2.40

Linux

(I used Ubuntu 22.04 mounted through Windows Subsystem for Linux (WSL) v2)

• C/C++ build tools

  sudo apt install build-essential
  

• CMake v3.27

  sudo snap install cmake --classic
  

• Doxygen v1.9

  sudo apt install doxygen gsfonts
  

• Graphviz v7.1

  cd ~
  mkdir tools
  cd tools
  wget https://gitlab.com/api/v4/projects/4207231/packages/generic/graphviz-releases/7.1.0/graphviz-7.1.0.tar.gz
  tar xzf graphviz-7.1.0.tar.gz
  cd graphviz-7.1.0
  ./configure
  make
  make install
  

  If doxygen generates errors about not supporting the PNG format (Format: "png" not recognized.), the following should fix that (later versions of graphviz might fix this "bug"). Note: This has been tested only Ubuntu. The "bug" is libgvplugin_gd.so.6 is not in /usr/local/lib/graphviz, which is where dot -c looks for plugins, so the following adds a symbolic link to the actual file:

  sudo ln /usr/local/bin/dot /usr/bin/dot
  sudo ln /usr/lib/x86_64-linux-gnu/graphviz/libgvplugin_gd.so.6.0.0 /usr/local/lib/graphviz/libgvplugin_gd.so.6
  sudo dot -c
  

• Python 3.10

  sudo apt install python310-full
  

• Rust v1.71.1 in release 2021

  curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
  

  Select option 1 (default) then follow the prompts.
• .Net SDK 7.0 (for C#)

  sudo apt install dotnet-sdk-7.0
  

Building the Code

1. Open a Git Bash prompt or Linux terminal and create a directory where to download the code. For example:

   cd ~
   mkdir work
   cd work
   

2. Use git to get the code from GitHub.com:

   git https://github.com/stephenlepisto/designpatternexamples.git
   

3. Go into the created directory:

   cd designpatternexamples
   

4. Create the build directory for cmake and go into it:

   mkdir build
   cd build
   

5. Use cmake to build everything:

   Windows

   cmake ..
   cmake --build . --config release
   

   Linux

   cmake .. -D CMAKE_BUILD_TYPE=Release
   cmake --build .
   

View the Code Documentation

After building everything, the following command lines displays Doxygen or Rust source documentation when run from a Windows Command Prompt (navigate to the build directory first, for example cd %HOMEPATH%\designpatternexamples\build).

Note: The documentation is not directly viewable on Linux unless a GUI and browser are loaded and even then, the following command line invocations will not work (load the browser and navigate to those files. If you want to play with a text-based browser such as lynx, be aware the diagrams will not be visible).

Documentation	Command Line/Location
Doxygen	html\index.html
Rust	rust\doc\design_pattern_examples_rust\index.html

Running the Examples

After building everything, the following command lines runs each example (navigate to the build directory first).

Language	Windows Command line	Linux Command Line
go to build	cd "%HOMEPATH%\designpatternexamples\build"	cd ~/work/designpatternexamples/build
C	c\release\DesignPatternExamples_c.exe	c/DesignPatternExamples_c
C++	cplusplus\release\DesignPatternExamples_cpp.exe	cplusplus/DesignPatternExamples_cpp
C#	csharp\release\DesignPatternExamples_csharp.exe	csharp/DesignPatternExamples_csharp
Python	py -m python.DesignPatternExamples_python	python3 -m python.DesignPatternExamples_python
Rust	rust\release\design_pattern_examples_rust.exe	rust/release/design_pattern_examples_rust

To get help for each set of examples, use --help switch after the command line. For example: c\release\DesignPatternExamples_c.exe --help

To run a single design pattern example in a language, add the name (or names) of the example after the command line (view all the names of examples with the --help option. For example: c\release\DesignPatternExamples_c.exe Flyweight).

Known Issues (all on Ubuntu Linux v22.04)

• Python
  • Flyweight can be skipped only with the Enter key.
  • Doxygen might produce two warnings:

    memento/memento.py:110: warning: unable to resolve reference to 'DesignPatternExamples_python.memento.memento.Memento_TextObject' for \ref command
    mediator/mediator_user_classes.py:37: warning: unable to resolve reference to 'DesignPatternExamples_python.mediator.mediator_user_classes.User' for \ref command
    

    This may be due to doxygen being v1.9.1 on Ubuntu. Doxygen v1.9.6 on Windows does not produce this warning (the fix might have occurred in v1.9.2).
• Rust
  • Flyweight can be skipped only with the Enter key.