Class: Twterm::Promise

Inherits:
Object
  • Object
show all
Defined in:
lib/twterm/promise.rb

Defined Under Namespace

Classes: Callback

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Promise

Returns a new instance of Promise.



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# File 'lib/twterm/promise.rb', line 3

def initialize
  @state = :pending
  @callbacks = []

  Thread.new do
    yield method(:resolve), method(:reject)
  end if block_given?
end

Class Method Details

.resolve(value) ⇒ Object 



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# File 'lib/twterm/promise.rb', line 70

def self.resolve(value)
  Promise.new { |resolve, _| resolve.(value) }
end

Instance Method Details

#catch(on_rejected = nil, &block) ⇒ Object 



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# File 'lib/twterm/promise.rb', line 12

def catch(on_rejected = nil, &block)
  if on_rejected.is_a?(Proc) && block_given?
    fail SyntaxError, 'both block arg and actual block given'
  end

  on_rejected ||= block
  self.then(nil, on_rejected)
end

#reject(reason) ⇒ Object 



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# File 'lib/twterm/promise.rb', line 21

def reject(reason)
  return if settled?

  @state = :rejected
  @reason = reason

  callbacks.each do |cb|
    cb.invoke_on_rejected(reason)
  end
  self
end

#resolve(value) ⇒ Object 



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# File 'lib/twterm/promise.rb', line 37

def resolve(value)
  return if settled?

  @state = :fulfilled
  @value = value

  callbacks.each do |cb|
    cb.invoke_on_fulfilled(value)
  end
  self
end

#then(on_fulfilled = nil, on_rejected = nil, &block) ⇒ Object 



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# File 'lib/twterm/promise.rb', line 49

def then(on_fulfilled = nil, on_rejected = nil, &block)
  if (on_fulfilled.is_a?(Proc) || on_rejected.is_a?(Proc)) && block_given?
    fail SyntaxError, 'both block arg and actual block given'
  end

  on_fulfilled ||= block
  next_promise = Promise.new
  callback = Callback.new(
    self,
    on_fulfilled.is_a?(Proc) ? on_fulfilled : nil,
    on_rejected.is_a?(Proc) ? on_rejected : nil,
    next_promise
  )
  @callbacks << callback

  callback.invoke_on_fulfilled(@value) if fulfilled?
  callback.invoke_on_rejected(@reason) if rejected?

  next_promise
end