swift-foundation

# Foundation

Foundation provides a base layer of functionality useful in many applications, including fundamental types for numbers, data, collections, and dates, as well as functions for task management, file system access, and more.

It is designed with these goals in mind:

* Provide a small set of basic utility types
* Enable a level of platform independence, to enhance portability
* Demonstrate useful conventions that can be widely adopted by the Swift ecosystem
* Support internationalization and localization to make software accessible around the world

This project, `swift-foundation`, provides a shared implementation of key Foundation API for all platforms.

On macOS, iOS, and other Apple platforms, apps should use the Foundation that comes with the operating system. The Foundation framework includes this code.

On all other Swift platforms, `swift-foundation` is available as part of the toolchain. Simply `import FoundationEssentials` or `import FoundationInternationalization` to use its API. It is also re-exported from [swift-corelibs-foundation](http://github.com/apple/swift-corelibs-foundation)'s `Foundation`, `FoundationXML`, and `FoundationNetworking` modules.

## Obtaining Foundation

Foundation is available in several forms — built into the OS on Apple platforms,
included in Swift toolchains, and as a Swift package. For guidance on which to
use and the tradeoffs involved, see [Distributions.md](Distributions.md).

> [!IMPORTANT]
> The swift-foundation package is intended to support development and testing of
> Foundation itself. It is not supported for use as a package dependency in
> other shipping projects. Prefer the built-in copy of Foundation that ships with 
> your toolchain or operating system instead.

## Building and Testing

> [!NOTE]
> Building swift-foundation requires a matching nightly Swift development snapshot toolchain. For example, building the `main` branch requires a nightly main toolchain and building the `release/6.4.x` branch requires a nightly 6.4 toolchain. You can download Swift nightly toolchains from [the Swift website](https://swift.org/install).

Before building Foundation, first ensure that you have a Swift toolchain installed. Next, check out the _Getting Started_ section of the [Foundation Build Process](Foundation_Build_Process.md#getting-started) guide for detailed steps on building and testing.


## Project Navigator

Foundation builds in different configurations and is composed of several projects.

```mermaid
  graph TD;
      FF[Foundation.framework]-->SF
      subgraph GitHub
        SCLF[swift-corelibs-foundation]-->SF
        SF[swift-foundation]-->FICU[swift-foundation-icu]
        SF-->SC[swift-collections]
      end   
```

### Swift Foundation

A shared library shipped in the Swift toolchain, written in Swift. It provides the core implementation of many key types, including `URL`, `Data`, `JSONDecoder`, `Locale`, `Calendar`, and more in the `FoundationEssentials` and `FoundationInterna