AttributeUI

This folder is primarily a container for the top-level pieces of the application. While you can remove some files and folders that this application does not use, be sure to read below before deciding what can be deleted and what needs to be kept in source control.

The following files are all needed to build and load the application.

"app.json" - The application descriptor which controls how the application is built and loaded.
"app.js" - The file that launches the application. This is primarily used to launch an instance of the MyApp.Application class.
"index.html" - The default web page for this application. This can be customized in "app.json".
"build.xml" - The entry point for Sencha Cmd to access the generated build script. This file is a place where you can hook into these processes and tune them. See the comments in that file for more information.
".sencha" - This (typically hidden) folder contains the generated build scripts and configuration files for the application. This folder is required in order to build the application but its content should not need to be edited in most cases. The content of this folder is updated by "sencha app upgrade".

These files can be ignored from source control as they are regenerated by the build process.

"build" - This folder contain the output of the build. The generated CSS file, consolidated resources and concatenated JavaScript file are all stored in this folder.
"bootstrap.*" - These files are generated by the build and watch commands to enable the application to load in "development mode".

Other Folders

Basic Application Structure

Applications that target a single toolkit will have the following structure.

app/                # Contains JavaScript code
    model/          # Data model classes
    view/           # Views as well as ViewModels and ViewControllers
    store/          # Data stores
    controller/     # Global / application-level controllers

overrides/          # JavaScript code that is automatically required

sass/
    etc/            # Misc Sass code (all.scss is imported by default)
    var/            # Sass variable and mixin declarations
    src/            # Sass rules

resources/          # Assets such as images, fonts, etc.

See the Sass readme for details on the "sass" folder.

Universal Applications

In a Universal Application, the basic application structure above is retained but only holds code, resources, etc. pieces that are used in both classic and modern build profiles. The following additional directories are used to isolate code and other files that are toolkit-specific:

classic/                # Content specific to the classic toolkit
    src/
        model/          # Data model classes
        view/           # Views as well as ViewModels and ViewControllers
        store/          # Data stores
        controller/     # Global / application-level controllers

    overrides/          # JavaScript code that is automatically required

    sass/
        etc/            # Misc Sass code (all.scss is imported by default)
        var/            # Sass variable and mixin declarations
        src/            # Sass rules

    resources/          # Assets such as images, fonts, etc.

modern/                 # Content specific to the modern toolkit
    src/
        model/          # Data model classes
        view/           # Views as well as ViewModels and ViewControllers
        store/          # Data stores
        controller/     # Global / application-level controllers

    overrides/          # JavaScript code that is automatically required

    sass/
        etc/            # Misc Sass code (all.scss is imported by default)
        var/            # Sass variable and mixin declarations
        src/            # Sass rules

    resources/          # Assets such as images, fonts, etc.

Overrides

The contents of "overrides" folders are automatically required and included in builds. These should not be explicitly mentioned in "requires" or "uses" in code. This area is intended for overrides like these:

Ext.define('AttributeUI.overrides.foo.Bar', {
    override: 'Ext.foo.Bar',
    ...
});

Such overrides, while automatically required, will only be included if their target class ("Ext.foo.Bar" in this case) is also required. This simplifies applying patches or extensions to other classes.