This small app try to demo a application framework for streamlit.

Basic idea:

1. Separate the layout and logic.
2. Use application states to control the layout since Streamlit will run the code repeatedly.
   • working_step is used

Class Definitions

1. class Env: used to access global variables st.session_state, make access the variable more readable
2. class Show: manage all layout
3. class App: implement all business logic

Two strategies to connect Show and App:

1. through global variables, Env

2. use instance, app in Show and show in App, which will combine two classes

   • direct access variable in eather class, or
   • use method call to encapsulate the detail

   we use 2nd method in the demo code.

Note:

• The "default way" Streamlit use to connect input widgets to st.session_state via "keywords" is a BAD concept. Hided in another global session variable and pass to on_change args is better.