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§Swift bindings backend for UniFFI

This module generates Swift bindings from a ComponentInterface definition, using Swift’s builtin support for loading C header files.

Conceptually, the generated bindings are split into two Swift modules, one for the low-level C FFI layer and one for the higher-level Swift bindings. For a UniFFI component named “example” we generate:

  • A C header file exampleFFI.h declaring the low-level structs and functions for calling into Rust, along with a corresponding exampleFFI.modulemap to expose them to Swift.

  • A Swift source file example.swift that imports the exampleFFI module and wraps it to provide the higher-level Swift API.

Most of the concepts in a ComponentInterface have an obvious counterpart in Swift, with the details documented in inline comments where appropriate.

To handle lifting/lowering/serializing types across the FFI boundary, the Swift code defines a protocol ViaFfi that is analogous to the uniffi::ViaFfi Rust trait. Each type that can traverse the FFI conforms to the ViaFfi protocol, which specifies:

  • The corresponding low-level type.
  • How to lift from and lower into into that type.
  • How to read from and write into a byte buffer.

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