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Nil Conditional Operator in Ruby
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README.md

News 21.10.2015

This proposal will be addressed by introducting native ruby operator .? as stated by Matz on 21.10.2015. See discussion here: https://bugs.ruby-lang.org/issues/11034#change-54502

nil-conditional

Nil Conditional Operator in Ruby.

This is my approach to create Nil Conditional Operator in Ruby.

This is very simple, and it is merely an experiment, so use it on your own risk.

Nil Conditional Operator is inspired by Null Conditional Operator introduced in C# 6.0.

Installation

nil_conditional is gemified and available on RubyGems.

Usage

Use _? method as Nil Conditional Operator. For example: logger._?.log('some debug information')

# logger is nil
logger.foo.bar.car.cow
NoMethodError: undefined method `foo` for #<NilClass>

# logger is nil
logger._?.foo.bar.car.cow
=> #<NilConditional>

# logger is not nil and all corresponding methods exist
logger._?.foo.bar.car.cow
=> "moooo"

# logger is not nil but doesn't have warn method
logger._?.warn('some warning')
=> #<NilConditional>

# logger is not nil and have warn method, but foo is invalid
# - first not nil value returned by receiver in train wreck breaks nil condition
logger._?.warn('some warning').foo
=> NoMethodError: undefined method `foo`

# ... but you can use nil conditional again
logger._?.warn('some warning')._?.foo
=> #<NilConditional>

# this works also with class methods
Object.non_existent_method
NoMethodError: undefined method `non_existent_method` for #<Object>

Object._?.non_existent_method
=> #<NilConditional>

# NilConditional object is eql to nil
Object.new._?.non_existent_method.nil?
=> true

NilConditional instances always return new NilConditional object if method is missing. Those objects are also eql to nil.

Changelog

  • Changes from version with major 1

    Previous version used different syntax

  • Changes from version with major 0

    • Previous version didn't support methods with special characters and there was no support for local variables.
    • Previous version used trailing _? as NilConditional operator. Current version uses preceding double underscore character __.

Discussion

Feel free to submit ideas via issues and discuss better solution to Nil Conditional Operator in Ruby

License

This is free software, licensed under MIT License. See LICENSE.txt file.

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