add: factory method example, not done yet

factoryMethod/.gitignore

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+# Xmake cache
+.xmake/
+build/
+
+# MacOS Cache
+.DS_Store
+
+

factoryMethod/doc/Note.md

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+# Factory Method
+
+The Factory Method is a creational design pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created. It is useful when the exact class of the object that needs to be created is determined by subclasses.
+
+For example, imagine a game where you need different types of characters: warriors, wizards, and archers. Instead of hardcoding object creation (e.g., using `new` everywhere), a Factory Method allows you to delegate this process to subclasses, making your code more flexible and easier to extend.
+
+## Pros
+
+1. It provides flexibility in object creation, allowing subclasses to decide which class to instantiate;
+2. It follows the Open/Closed Principle by enabling easy extension without modifying existing code;
+3. Helps reduce the dependency between client code and specific concrete classes.
+
+## Cons
+
+1. Can increase code complexity due to the need for multiple subclasses;
+2. Introducing many factory classes for minor variations in object creation might lead to overcomplication.
+
+## References
+
+1. [Factory Method on Refactoring.Guru](https://refactoring.guru/design-patterns/factory-method)
+2. [Factory Pattern. When to use factory methods?](https://stackoverflow.com/questions/69849/factory-pattern-when-to-use-factory-methods)

factoryMethod/src/main.cpp

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+#include <iostream>
+
+using namespace std;
+
+int main(int argc, char** argv)
+{
+    cout << "hello world!" << endl;
+    return 0;
+}

factoryMethod/xmake.lua

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+add_rules("mode.debug", "mode.release")
+
+target("factoryMethod")
+    set_kind("binary")
+    add_files("src/*.cpp")
+
+--
+-- If you want to known more usage about xmake, please see https://xmake.io
+--
+-- ## FAQ
+--
+-- You can enter the project directory firstly before building project.
+--
+--   $ cd projectdir
+--
+-- 1. How to build project?
+--
+--   $ xmake
+--
+-- 2. How to configure project?
+--
+--   $ xmake f -p [macosx|linux|iphoneos ..] -a [x86_64|i386|arm64 ..] -m [debug|release]
+--
+-- 3. Where is the build output directory?
+--
+--   The default output directory is `./build` and you can configure the output directory.
+--
+--   $ xmake f -o outputdir
+--   $ xmake
+--
+-- 4. How to run and debug target after building project?
+--
+--   $ xmake run [targetname]
+--   $ xmake run -d [targetname]
+--
+-- 5. How to install target to the system directory or other output directory?
+--
+--   $ xmake install
+--   $ xmake install -o installdir
+--
+-- 6. Add some frequently-used compilation flags in xmake.lua
+--
+-- @code
+--    -- add debug and release modes
+--    add_rules("mode.debug", "mode.release")
+--
+--    -- add macro definition
+--    add_defines("NDEBUG", "_GNU_SOURCE=1")
+--
+--    -- set warning all as error
+--    set_warnings("all", "error")
+--
+--    -- set language: c99, c++11
+--    set_languages("c99", "c++11")
+--
+--    -- set optimization: none, faster, fastest, smallest
+--    set_optimize("fastest")
+--
+--    -- add include search directories
+--    add_includedirs("/usr/include", "/usr/local/include")
+--
+--    -- add link libraries and search directories
+--    add_links("tbox")
+--    add_linkdirs("/usr/local/lib", "/usr/lib")
+--
+--    -- add system link libraries
+--    add_syslinks("z", "pthread")
+--
+--    -- add compilation and link flags
+--    add_cxflags("-stdnolib", "-fno-strict-aliasing")
+--    add_ldflags("-L/usr/local/lib", "-lpthread", {force = true})
+--
+-- @endcode
+--
+