Source Layouts

The modules that swift build creates are determined from the filesystem layout of your source files.

For example, if you created a directory with the following layout:

example/
example/Sources/bar.swift
example/Sources/baz.swift

Running swift build within directory example would produce a single library target: example/.build/debug/example.a

To create multiple modules create multiple subdirectories:

example/Sources/foo/foo.swift
example/Sources/bar/bar.swift

Running swift build would produce two library targets:

To generate an executable module (instead of a library module) add a main.swift file to that module’s subdirectory:

example/Sources/foo/main.swift
example/Sources/bar/bar.swift

Running swift build would now produce:

Where foo is an executable and bar.a a static library.

Other Rules

Sub directories of directory named Tests become test-modules and are executed by swift test. Tests or any subdirectory can be excluded via Manifest file.
Sub directories of a directory named Sources, Source, srcs or src become modules.
It is acceptable to have no Sources directory, in which case the root directory is treated as a single module (place your sources there) or sub directories of the root are considered modules. Use this layout convention for simple projects.