Popularity
4.1
Growing
Activity
0.0
Declining
17
2
0

Programming language: Crystal
License: MIT License
Tags: Dependency Injection    
Latest version: v0.4.2

HardWire alternatives and similar shards

Based on the "Dependency Injection" category.
Alternatively, view HardWire alternatives based on common mentions on social networks and blogs.

Do you think we are missing an alternative of HardWire or a related project?

Add another 'Dependency Injection' Shard

README

HardWire โšก

Crystal CI

A Compile-time Dependency Injection system for Crystal.

Installation

  1. Add the dependency to your shard.yml:
dependencies:
  hardwire:
    github: jerometwell/hardwire
  1. Run shards install

Usage

require "hardwire"

Hardwire is designed to operate inside a container object. Since the resolution is compile-time (Using Macros), normally this will be a module.

Creating a container ๐Ÿ“ฆ

# To create a new container, include `HardWire::Container`
# This will add the macros you need to register and resolve wiring
module Container
  include HardWire::Container

  # use transient/singleton to wire different lifecycles
  # singleton dependencies will be memoized
  # dependencies for the constructor will be resolved from the constructor automatically
  transient Dependency
  singleton NeedsDependency

  # you can also register dependencies with a block instead of inspecting the constructor
  # Your block MUST return an instance of the class you are registering
  singleton NeedsDependency {
    NeedsDependency.new( self.resolve Dependency )
  }
end

Hardwire tries to operate with minimal modifications to other classes (unless required). "simple" classes, e.g.

  • Have a single constructor
  • Have unique dependencies/do not require tags

If your classes match this signature, you can wire up in the container without adding anything to the classes.

For everything else, there's:

Multiple Constructors ๐Ÿšง

Hardwire needs to know which constuctor function to use.

Annotate your "Injectable" constructor with the Hardwire::Inject annotation.

class MultipleInits
  @[HardWire::Inject]
  def initialize(input: String)
    # register will inspect this method's arguments
    # [...]
  end

  def initialize
    # will not be used for injection
    # [...]
  end
end

Tags ๐Ÿท

To differentiate between registrations of the same type, use the HardWire::Tags annotation. Tags allow you to attach additional metadata to the signature. Tags themselves are string-based, simple identifiers (/\w+/) that allow you to resolve a different registration of the same class.

# [...]

# registering a transient dependency with tag "secret"
transient String, "secret" {
  "a secret string"
}

# registering a singleton
# When no tags are set, it is considered the "default" registration
singleton DbService

# registering a different singleton with a tag
singleton DbService, "primary"

# Resolving Dependencies
class Resolving
  @[Hardwire::Tags(input: "secret", primary_db: "primary")]
  def initialize(input : String, primary_db : DbService, default_db : DbService)
  end
end

Resolving Manually ๐Ÿ”จ

You can resolve dependencies manually using the .resolve macro. This allows you to resolve dependencies manually with the tag string.

module Container
  include HardWire::Container

  transient SecretService, "primary"
  singleton DatabaseThing
end

service = Container.resolve SecretService, "primary"
db = Container.resolve DatabaseThing

Runtime Interrogation ๐Ÿ‘€

Hardwire can tell you information about the registrations at runtime, but the dependencies are HardWired (See what I did there?), so they can't be changed.

module Container
  include HardWire::Container

  singleton DbService
end

Container.registered?(DbService) # true
Container.registered?(DbService, "tagged") # false
Container.registered?(String) # false

Contributing

  1. Fork it (https://github.com/jerometwell/hardwire/fork)
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request

Contributors