swift-hashed

Hashable wrapper type and a set of explicit hashing strategies.

Table of Contents

• Motivation
• Features
  • Predefined comparators
• Installation
  • Basic
  • Recommended
• License

Motivation

Swift strongly encourages Hashable, especially when working with collections, diffing, and identity-based logic.

In practice, however, hashing often becomes problematic at API boundaries:

• values erased to any
• reference types without stable identity
• types you don’t own
• generic code that cannot add Hashable constraints
• contexts where different hashing strategies are required

This is especially visible when working with KeyPath-based APIs, where generic composition frequently destroys compile-time Hashable conformance.

Features

Hashed is a lightweight Hashable container that lets you define equality explicitly, while keeping call sites terse.

Predefined hashers

Choose how two values should be compared using a Hashed.Hasher:

Automatic

The detectHashable comparator attempts to cast values to any Hashable and compare them using native hash(into hasher: inout Swift.Hasher) method:

.detectHashable(fallback: Hasher = .dump)

If hashable cast is not possible, the provided fallback hasher is used.

Building blocks

• .empty – nothing is combined into `Swift.Hasher``
• .custom((Value, inout Swift.Hasher) -> Void) – full control
• .dump – hashes the textual dump() output

Hashable-driven

• .defaultHashable – equivalent to using native hash(into hasher: Swift.Hasher) method

Property-based

The property hashable hashes values by a derived hashable projection:

.property(\.someHashableProperty)
.property { String(reflecting: $0) }

• .objectID – hash reference identity (only when Value: AnyObject)

Error convenience

The .localizedDescription hasher is equivalent to .property(\.localizedDescription).

It is typically most useful as a fallback, for example:

.detectHashable(fallback: .localizedDescription)

Concurrency escape hatches

• .uncheckedSendable((Value) -> any Hashable)

  A property-style comparator for non-sendable projections

• .uncheckedSendable((Value, inout Swift.Hasher) -> Void)

  A custom-style comparator for non-sendable values

Note

Most users should prefer .detectHashable() or .property hashers

Installation

Basic

You can add Hashed to an Xcode project by adding it as a package dependency.

1. From the File menu, select Swift Packages › Add Package Dependency…
2. Enter "https://github.com/capturecontext/swift-hashed" into the package repository URL text field
3. Choose products you need to link them to your project.

Recommended

If you use SwiftPM for your project structure, add Hashed to your package file.

.package(
  url: "git@github.com:capturecontext/swift-hashed.git",
  .upToNextMinor(from: "0.0.1")
)

or via HTTPS

.package(
  url: "https://github.com:capturecontext/swift-hashed.git",
  .upToNextMinor("0.0.1")
)

Do not forget about target dependencies:

.product(
  name: "Hashed",
  package: "swift-hashed"
)

License

This library is released under the MIT license. See LICENSE for details.