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https://github.com/stevenharman/dumb_delegator
Delegator and SimpleDelegator in Ruby's stdlib are useful, but they pull in most of Kernel. This is not appropriate for many uses; for instance, delegation to Rails models.
https://github.com/stevenharman/dumb_delegator
design-patterns proxy-object ruby simpledelegator
Last synced: 2 days ago
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Delegator and SimpleDelegator in Ruby's stdlib are useful, but they pull in most of Kernel. This is not appropriate for many uses; for instance, delegation to Rails models.
- Host: GitHub
- URL: https://github.com/stevenharman/dumb_delegator
- Owner: stevenharman
- License: mit
- Created: 2012-03-20T02:35:24.000Z (almost 13 years ago)
- Default Branch: main
- Last Pushed: 2024-12-17T16:11:48.000Z (28 days ago)
- Last Synced: 2025-01-05T09:01:57.313Z (9 days ago)
- Topics: design-patterns, proxy-object, ruby, simpledelegator
- Language: Ruby
- Homepage:
- Size: 77.1 KB
- Stars: 65
- Watchers: 5
- Forks: 6
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# DumbDelegator
[](https://badge.fury.io/rb/dumb_delegator)
[](https://github.com/stevenharman/dumb_delegator/actions/workflows/ci.yml)
[](https://codeclimate.com/github/stevenharman/dumb_delegator/maintainability)
[](https://codeclimate.com/github/stevenharman/dumb_delegator/test_coverage)
Ruby provides the `delegate` standard library.
However, we found that it is not appropriate for cases that require nearly every call to be proxied.
For instance, Rails uses `#class` and `#instance_of?` to introspect on Model classes when generating forms and URL helpers.
These methods are not forwarded when using `Delegator` or `SimpleDelegator`.
```ruby
require "delegate"
class MyAwesomeClass
# ...
end
o = MyAwesomeClass.new
d = SimpleDelegator.new(o)
d.class #=> SimpleDelegator
d.is_a? MyAwesomeClass #=> false
```
`DumbDelegator`, on the other hand, forwards almost ALL THE THINGS:
```ruby
require "dumb_delegator"
class MyAwesomeClass
# ...
end
o = MyAwesomeClass.new
d = DumbDelegator.new(o)
d.class #=> MyAwesomeClass
d.is_a? MyAwesomeClass #=> true
```
## Installation
Add this line to your Gemfile:
```ruby
gem "dumb_delegator"
```
And then install:
```bash
$ bundle
```
Or install it yourself:
```bash
$ gem install dumb_delegator
```
### Versioning
This project adheres to [Semantic Versioning][semver].
#### Version `0.8.x`
The `0.8.0` release was downloaded 1.2MM times before the `1.0.0` work began.
Which is great! 🎉
But, we wanted to clean up some cruft, fix a few small things, and improve ergonomics.
And we wanted to do all of that while, hopefully, not breaking existing usage.
To that end, `1.0.0` dropped support for all [EoL'd Rubies][ruby-releases] and only officially supported Ruby `2.4` - `2.7` when it was released.
However, most older Rubies, _should_ still work.
Maybe… Shmaybe?
Except for Ruby 1.9, which probably _does not work_ with `DumbDelegator` `> 1.0.0`.
If you're on an EoL'd Ruby, please try the `0.8.x` versions of this gem.
## Usage
`DumbDelegator`'s API and usage patters were inspired by Ruby stdlib's `SimpleDelegator`.
So the usage and ergonomics are quite similar.
```ruby
require "dumb_delegator"
class Coffee
def cost
2
end
def origin
"Colombia"
end
end
class Milk < DumbDelegator
def cost
super + 0.4
end
end
class Sugar < DumbDelegator
def cost
super + 0.2
end
end
coffee = Coffee.new
cup_o_coffee = Sugar.new(Milk.new(coffee))
cup_o_coffee.origin #=> Colombia
cup_o_coffee.cost #=> 2.6
# Introspection
cup_o_coffee.class #=> Coffee
cup_o_coffee.__getobj__ #=> #
cup_o_coffee.inspect #=> "#>>"
cup_o_coffee.is_a?(Coffee) #=> true
cup_o_coffee.is_a?(Milk) #=> true
cup_o_coffee.is_a?(Sugar) #=> true
```
### Rails Model Decorator
There are [many decorator implementations](http://robots.thoughtbot.com/post/14825364877/evaluating-alternative-decorator-implementations-in) in Ruby.
One of the simplest is "`SimpleDelegator` + `super` + `__getobj__`," but it has the drawback of confusing Rails.
It is necessary to redefine `#class`, at a minimum.
If you're relying on Rails' URL Helpers with a delegated object, you also need to redefine `#instance_of?`.
We've also observed the need to redefine other Rails-y methods to get various bits of 🧙 Rails Magic 🧙 to work as expected.
With `DumbDelegator`, there's not a need for redefining these things because nearly every possible method is delegated.
### Optional `case` statement support
Instances of `DumbDelegator` will delegate `#===` out of the box.
Meaning an instance can be used in a `case` statement so long as the `when` clauses rely on instance comparison.
For example, when using a `case` with a regular expression, range, etc...
It's also common to use Class/Module in the `where` clauses.
In such usage, it's the Class/Module's `::===` method that gets called, rather than the `#===` method on the `DumbDelegator` instance.
That means we need to override each Class/Module's `::===` method, or even monkey-patch `::Module::===`.
`DumbDelegator` ships with an optional extension to override a Class/Module's `::===` method.
But you need to extend each Class/Module you use in a `where` clause.
```ruby
def try_a_case(thing)
case thing
when MyAwesomeClass
"thing is a MyAwesomeClass."
when DumbDelegator
"thing is a DumbDelegator."
else
"Bad. This is bad."
end
end
target = MyAwesomeClass.new
dummy = DumbDelegator.new(target)
try_a_case(dummy) #=> thing is a DumbDelegator.
MyAwesomeClass.extend(DumbDelegator::TripleEqualExt)
try_a_case(dummy) #=> thing is a MyAwesomeClass.
```
#### Overriding `Module::===`
If necessary, you could also override the base `Module::===`, though that's pretty invasive.
🐲 _There be dragons!_ 🐉
```ruby
::Module.extend(DumbDelegator::TripleEqualExt)
```
## Contributing
1. Fork it
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Added some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create new Pull Request
## Contribution Ideas/Needs
1. Ruby 1.8 support (use the `blankslate` gem?)
[ruby-releases]: https://www.ruby-lang.org/en/downloads/branches/ "The current maintenance status of the various Ruby branches"
[semver]: https://semver.org/spec/v2.0.0.html "Semantic Versioning 2.0.0"