Sha256: 62078ad6d62ea82a8913db38145fff8523d77a3be374393423da05d53623385c
Contents?: true
Size: 1.9 KB
Versions: 6
Compression:
Stored size: 1.9 KB
Contents
require 'concurrent/promise'
require 'dry/monads/task'
module Dry
module Monads
# Lazy is a twin of Task which is always executed on the current thread.
# The underlying mechanism provided by concurrent-ruby ensures the given
# computation is evaluated not more than once (compare with the built-in
# lazy assignement ||= which does not guarantee this).
class Lazy < Task
class << self
# @private
def new(promise = nil, &block)
if promise
super(promise)
else
super(Concurrent::Promise.new(executor: :immediate, &block))
end
end
private :[]
end
# Forces the compution and returns its value.
#
# @return [Object]
def value!
@promise.execute.value!
end
alias_method :force!, :value!
# Forces the computation. Note that if the computation
# thrown an error it won't be re-raised as opposed to value!/force!.
#
# @return [Lazy]
def force
@promise.execute
self
end
# @return [String]
def to_s
state = case promise.state
when :fulfilled
value!.inspect
when :rejected
"!#{ promise.reason.inspect }"
else
'?'
end
"Lazy(#{ state })"
end
alias_method :inspect, :to_s
# Lazy constructors
#
module Mixin
# @see Dry::Monads::Lazy
Lazy = Lazy
# @see Dry::Monads::Unit
Unit = Unit
# Lazy constructors
module Constructors
# Lazy computation contructor
#
# @param block [Proc]
# @return [Lazy]
def Lazy(&block)
Lazy.new(&block)
end
end
include Constructors
end
end
extend Lazy::Mixin::Constructors
end
end
Version data entries
6 entries across 6 versions & 1 rubygems