In Xcode 6 beta 4, Swift adds support for access control. This gives you complete control over what part of the code is accessible within a single file, available across your project, or made public as API for anyone that imports your framework. The three access levels included in this release are:
privateentities are available only from within the source file where they are defined.
internalentities are available to the entire module that includes the definition (e.g. an app or framework target).
publicentities are intended for use as API, and can be accessed by any file that imports the module, e.g. as a framework used in several of your projects.
Read more on Apple's Swift Blog