Class: Qo::Matchers::PatternMatch

Inherits:
Object
  • Object
show all
Defined in:
lib/qo/matchers/pattern_match.rb

Overview

Creates a PatternMatch, which will evaluate once given a match target.

Each GuardBlockMatcher given will be run in sequence until a “match” is located. Once that condition is met, it will call the associated block function of that GuardBlockMatcher with the match target.

This is done as an effort to emulate Right Hand Assignment seen in other functionally oriented languages pattern matching systems. Most notably this is done in Scala: (docs.scala-lang.org/tour/pattern-matching.html)

“‘scala notification match 

case Email(email, title, _) =>
  s"You got an email from $email with title: $title"

case SMS(number, message) =>
  s"You got an SMS from $number! Message: $message"

case VoiceRecording(name, link) =>
  s"You received a Voice Recording from $name! Click the link to hear it: $link"

case other => other

“‘

Qo will instead pipe the entire matched object, and might look something like this:

“‘ruby # Assuming notification is in the form of a tuple

Qo.match(notification,

Qo.m(EMAIL_REGEX, String, :*) { |email, title, _|
  "You got an email from #{email} with title: #{title}"
},

Qo.m(PHONE_REGEX, String) { |number, message, _|
  "You got an SMS from #{number}! Message: #{message}"
},

Qo.m(String, LINK_REGEX) { |name, link, _|
  "You received a Voice Recording from #{name}! Click the link to hear it: #{link}"
},

Qo.m(:*)

) “‘

Efforts to emulate the case class mechanic may be present in later versions, but for now the associated performance penalty may be too steep to consider.

We’ll evaluate those options in a few experiments later.

Author:

  • baweaver

Instance Method Summary collapse

Constructor Details

#initialize(*matchers) ⇒ PatternMatch

Returns a new instance of PatternMatch.

Raises:



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# File 'lib/qo/matchers/pattern_match.rb', line 60

def initialize(*matchers)
  raise Qo::Exceptions::NotAllGuardMatchersProvided unless matchers.all? { |q|
    q.is_a?(Qo::Matchers::GuardBlockMatcher)
  }

  @matchers = matchers
end

Instance Method Details

#call(target) ⇒ Any | nil

Immediately invokes a PatternMatch

Parameters:

  • target (Any) —

    Target to run against and pipe to the associated block if it “matches” any of the GuardBlocks

Returns:

  • (Any | nil) —

    Result of the piped block, or nil on a miss



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# File 'lib/qo/matchers/pattern_match.rb', line 83

def call(target)
  @matchers.each { |guard_block_matcher|
    did_match, match_result = guard_block_matcher.call(target)
    return match_result if did_match
  }

  nil
end

#to_proc ⇒ Proc

Function return of a PatternMatch waiting for a target to run

Returns:

  • (Proc) —

    Any -> Any | nil



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# File 'lib/qo/matchers/pattern_match.rb', line 72

def to_proc
  Proc.new { |target| self.call(target) }
end