8000 Add Multiton Object Scope changes and PR documentation by spencer-edgecombe · Pull Request #584 · Swinject/Swinject · GitHub
[go: up one dir, main page]
More Web Proxy on the site http://driver.im/
Skip to content

Add Multiton Object Scope changes and PR documentation #584

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Add Multiton Object Scope changes and PR documentation #584

wants to merge 1 commit into from

Conversation

spencer-edgecombe
Copy link

Add Multiton Object Scope to Swinject

Summary

This PR introduces a new object scope called multiton to Swinject. The multiton scope caches instances based on the arguments passed during resolution, allowing the same instance to be returned when resolving with identical arguments.

Motivation

The multiton pattern is useful in scenarios where you want to:

  • Share instances based on configuration parameters
  • Implement a factory pattern where instances are cached by their initialization arguments
  • Reduce memory usage and initialization overhead for objects that are expensive to create
  • Maintain consistency when the same configuration should always yield the same instance

Changes

Added

  1. New Object Scope: .multiton

    • Added MultitonStorage class in Sources/InstanceStorage.swift
    • Registered the scope in Sources/ObjectScope.Standard.swift
    • Instances are cached using arguments as keys

  2. Extended InstanceStorage Protocol

    • Added new methods with default implementations for backward compatibility:
      • func instance(inGraph:withArguments:) -> Any?
      • func setInstance(_:inGraph:withArguments:)

  3. Container Resolution Enhancement

    • Added resolveWithArgumentCapture method to extract and pass arguments to multiton storage
    • Modified resolution logic to handle multiton scope specially
    • Added support for argument extraction from tuples up to 9 arguments

  4. Documentation

    • Added multiton scope documentation in Documentation/ObjectScopes.md
    • Updated README.md to include multiton in the feature list

  5. Tests

    • Added comprehensive test suite in Tests/SwinjectTests/ContainerTests.Multiton.swift
    • Tests cover single arguments, multiple arguments, no arguments, and resetObjectScope

Modified

  1. Container.swift

    • Updated _resolve method to detect multiton storage and use argument capture
    • Modified resolveAsWrapper to support multiton scope for wrapped types
    • Updated resolve method to pass arguments to storage methods

  2. InstanceStorage.swift

    • Added default implementations to maintain backward compatibility

Usage

// Register a service with multiton scope
container.register(Animal.self) { _, name in
    Cat(name: name)
}
.inObjectScope(.multiton)

// Resolve with arguments
let cat1 = container.resolve(Animal.self, argument: "Mimi")
let cat2 = container.resolve(Animal.self, argument: "Mimi")
let cat3 = container.resolve(Animal.self, argument: "Mew")

// cat1 === cat2 (same instance for same arguments)
// cat1 !== cat3 (different instance for different arguments)

Important Notes

  • Arguments must be Hashable: The multiton scope requires arguments to be hashable to use them as cache keys
  • Memory considerations: Cached instances are held strongly until resetObjectScope(.multiton) is called
  • Thread safety: The implementation maintains the same thread safety guarantees as other Swinject scopes

Implementation Details

The multiton storage uses a dictionary to cache instances by their arguments. When arguments are provided during resolution:

  1. Arguments are extracted from the resolver's tuple format
  2. Arguments are converted to a hashable representation
  3. The cache is checked for an existing instance with those arguments
  4. If found, the cached instance is returned; otherwise, a new instance is created and cached

For cases with no arguments, a special sentinel value is used as the cache key.

Testing

The implementation includes comprehensive tests covering:

  • Single argument caching
  • Multiple argument caching
  • No argument scenarios
  • Scope reset functionality
  • Integration with existing Swinject features

Breaking Changes

None. The implementation maintains full backward compatibility through default protocol implementations.

Performance Impact

Minimal. The multiton scope adds a small overhead for:

  • Argument extraction (only for multiton-scoped services)
  • Hash computation for cache keys
  • Dictionary lookup for cached instances

This overhead is negligible compared to the potential savings from reusing instances.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers
No reviews
Assignees
No one assigned
Labels
None yet
Projects
None yet
Milestone
No milestone
Development

Successfully merging this pull request may close these issues.
1 participant
@spencer-edgecombe
0