Royale applications are usually comprised of many files. If you are in rapid-prototyping or proof-of-concept “get something small running quickly” mode, you can cram everything into one file. But breaking things into multiple pieces often helps you organize or create “separation of concerns”, and as your project and team grows, you and your teammates can work on individual pieces independently without stepping on each other's work. Finally, coherent pieces that perform some standard function or provide a common user experience (like a login form and its related logic) can more easily be re-used in other applications.
There are multiple popular ways of dividing an Application into coherent and reusable pieces: Model-View (MV), Model-View-Controller (MVC), and other alphabet soup like MVP, MVVM, HMVC and more. This documentation will not address these patterns in detail. You can read more about them on the internet.
Whatever you decide for how many files you will have, another thing to keep in mind is that Royale can produce different kinds of output, like SWFs for Adobe FlashPlayer or Adobe AIR as well as HTML/JS/CSS for browsers and Apache Cordova applications. So, the recommended practice is to create a folder for your project files and a set of subfolders within it. The Royale compiler detects certain common folder patterns and automatically chooses where to put output folders, although you can override that if you desire.
If you are using an IDE that supports Royale, it will create the standard folder structure for you when you create a Royale project. If you are working outside of an IDE, and perhaps using command-line instructions to compile your code, here is how to structure your project.
Let's say you are creating a project called MyFirstRoyaleApp. Create a MyFirstRoyaleApp folder and in it create a folder named “src”. Put your source code in there. If you do that, the compiler will put the output in a “bin” folder that it creates.
If you use Apache Maven to build your app, you can use one of the Maven archetypes, which put the main application source code 3 levels deep in a “src/main/royale” folder structure. Other kinds of files then go in “src/main/resource”, “src/main/config” and so on. Maven instructs the compiler to put the output in a “target/javascript/bin” folder.
Most Royale applications use an MXML file as the main application file. Other files are written in MXML or ActionScript depending on whether you are assembling pieces or writing custom logic. You can write a Royale Application without using MXML at all, but you'll end up writing more code.
So, if you decide to use MXML as your main application file, then your folder structure might look like this:
-MyFirstRoyaleApp |-src/MyFirstRoyaleApp.mxml
And after compilation you will see:
-MyFirstRoyaleApp
|-src
|-MyFirstRoyaleApp.mxml
|-bin
|-js-debug
|-index.html
|-MyFirstRoyaleApp.js
|-MyFirstRoyaleApp.css
|-(lots of other files)
If you create a production version, you will also see:
|-bin
|-js-release
|-index.html
|-MyFirstRoyaleApp.js
|-MyFirstRoyaleApp.css