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# frozen_string_literal: true
module ActiveRecord
class Promise < BasicObject
undef_method :==, :!, :!=
def initialize(future_result, block) # :nodoc:
@future_result = future_result
@block = block
end
# Returns whether the associated query is still being executed or not.
def pending?
@future_result.pending?
end
# Returns the query result.
# If the query wasn't completed yet, accessing +#value+ will block until the query completes.
# If the query failed, +#value+ will raise the corresponding error.
def value
return @value if defined? @value
result = @future_result.result
@value = if @block
@block.call(result)
else
result
end
end
# Returns a new +ActiveRecord::Promise+ that will apply the passed block
# when the value is accessed:
#
# Post.async_pick(:title).then { |title| title.upcase }.value
# # => "POST TITLE"
def then(&block)
Promise.new(@future_result, @block ? @block >> block : block)
end
[:class, :respond_to?, :is_a?].each do |method|
define_method(method, ::Object.instance_method(method))
end
def inspect # :nodoc:
"#<ActiveRecord::Promise status=#{status}>"
end
def pretty_print(q) # :nodoc:
q.text(inspect)
end
private
def status
if @future_result.pending?
:pending
elsif @future_result.canceled?
:canceled
else
:complete
end
end
class Complete < self # :nodoc:
attr_reader :value
def initialize(value)
@value = value
end
def then
Complete.new(yield @value)
end
def pending?
false
end
private
def status
:complete
end
end
end
end
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