Class: Promise

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

Constant Summary collapse

VERSION = 
"0.0.1"

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(&block) ⇒ Promise

Returns a new instance of Promise.



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# File 'lib/promise.rb', line 7

def initialize(&block)
  @state = :pending
  @value = nil
  @reason = nil
  @callbacks = []
  @errbacks = []
  instance_eval(&block) if block_given?
end

Instance Attribute Details

#reason ⇒ Object (readonly)

Returns the value of attribute reason.



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# File 'lib/promise.rb', line 5

def reason
  @reason
end

#state ⇒ Object (readonly)

Returns the value of attribute state.



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# File 'lib/promise.rb', line 5

def state
  @state
end

#value ⇒ Object (readonly)

Returns the value of attribute value.



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# File 'lib/promise.rb', line 5

def value
  @value
end

Instance Method Details

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



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# File 'lib/promise.rb', line 20

def then(on_fulfilled = nil, on_rejected = nil)
  result = Promise.new

  call_and_fulfill = ->(value) {
    begin
      if function?(on_fulfilled)
        new_value = on_fulfilled.call(value)
        if Promise === new_value
          new_value.then(->(v) { result.fulfill(v) }, ->(r) { result.reject(r) })
        else
          result.fulfill(new_value)
        end
      else
        result.fulfill(value)
      end
    rescue Exception => e
      result.reject(e)
    end
  }

  call_and_reject = ->(reason) {
    begin
      if function?(on_rejected)
        new_value = on_rejected.call(reason)
        if Promise === new_value
          new_value.then(->(v) { result.fulfill(v) }, ->(r) { result.reject(r) })
        else
          result.fulfill(new_value)
        end
      else
        result.reject(reason)
      end
    rescue Exception => e
      result.reject(e)
    end
  }

  case @state
  when :pending
    @callbacks << call_and_fulfill
    @errbacks << call_and_reject
  when :fulfilled
    call_and_fulfill.call(@value)
  when :rejected
    call_and_reject.call(@reason)
  end

  result
end