In order to better understand how and why Flysystem works the way it does, several concepts require some explanation.
The main entry point for the file system API is the FilesystemInterface. When working with file systems, this is the class you’ll want to be talking to.
Flysystem works the way it does because of its use of the adapter pattern. The inconsistencies of the different file systems are eliminated in these adapters.
While adapters have a public interface (publicly accessible methods), they should be considered internal.
Portability is a very important concept within Flysystem. In order to roll out this aspect to the fullest, all paths in Flysystem are relative. File system root paths, whether remote or local, are viewed as endpoints. Because of this, file systems are movable independently. This allows parts of the application file handling to move to other storage types, while the majority is in a centralized location.
Like the storage type, root paths are an implementation detail. When root paths are defined as configuration, the stability of your code improves.
Flysystem has a files first approach. Storage systems like AWS S3 are linear file systems, this means the path to a file is used as an identifier, rather than a representation of all the directories it’s nested in.
This means directories are second class citizens. Because of this, directories will be automatically created on file systems that require them when writing files. Not only does this make handling writes a lot easier, it also ensures a consistent behaviors across all file system types.