Class: Dharma::Promise

Inherits:
Object
  • Object
show all
Includes:
PromiseActions
Defined in:
lib/dharma/promise.rb

Class Method Summary collapse

Instance Method Summary collapse

Methods included from PromiseActions

#complete_with, #failed, #failure, #flat_map, #map, #on_failure, #on_success, #recover, #recover_with, #success, #try_failure, #try_success

Constructor Details

#initialize ⇒ Promise

Returns a new instance of Promise.



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# File 'lib/dharma/promise.rb', line 17

def initialize
  @mutex     = Monitor.new
  @condition = @mutex.new_cond
end

Class Method Details

.failed(value) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 13

def self.failed(value)
  KeptPromise.new(value, :failure)
end

.successful(value) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 9

def self.successful(value)
  KeptPromise.new(value, :success)
end

Instance Method Details

#complete(value, as = nil) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 72

def complete(value, as = nil)
  if try_complete(value, as)
    self
  else
    raise Dharma::IllegalStateException.new("Promise already completed.")
  end
end

#completed? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/dharma/promise.rb', line 66

def completed?
  @mutex.synchronize do
    @as != nil
  end
end

#failure? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/dharma/promise.rb', line 22

def failure?
  @mutex.synchronize do
    @as == :failure
  end
end

#on_complete(cb = nil, &block) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 111

def on_complete(cb = nil, &block)
  cb ||= block
  value, as = nil

  @mutex.synchronize do
    if @as
      value, as = @value, @as
    else
      (@on_completed ||= []) << cb
      return
    end
  end

  cb.call(value, as)
  return
end

#ready(at_most = nil) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 40

def ready(at_most = nil)
  @mutex.synchronize do
    if @as
      return self
    else
      @condition.wait(at_most ? at_most.to_f : nil)

      if @as
        return self
      else
        raise Dharma::TimeoutException.new("Futures timed out after [#{at_most}]")
      end
    end
  end
end

#resolve_and_assign(value, as = nil) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 128

def resolve_and_assign(value, as = nil)
  case as
  when :failure
    case value
    when Exception
      @value, @as = value, as
    else
      @value, @as = Dharma::PromiseFailure.new(value), as
      @value.set_backtrace(caller)
    end
  when :success
    @value, @as = value, as
  else
    case value
    when LocalJumpError
      @value, @as = value.exit_value, :success
    when Exception
      @value, @as = value, :failure
    else
      @value, @as = value, :success
    end
  end
end

#result(at_most = nil) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 28

def result(at_most = nil)
  ready(at_most)

  @mutex.synchronize do
    if @as == :failure
      raise @value
    else
      return @value
    end
  end
end

#try_complete(value, as = nil) ⇒ Object 



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# File 'lib/dharma/promise.rb', line 80

def try_complete(value, as = nil)
  on_completed = nil

  @mutex.synchronize do
    if !@as
      resolve_and_assign(value, as)

      # Grab the value from what we stored
      value, as = @value, @as

      # Clear callbacks
      on_completed = @on_completed
      @on_completed = nil

      # Wake everyone up
      @condition.broadcast

      # We don't need the condition anymore
      @condition = nil
    else
      return false
    end
  end

  if on_completed
    on_completed.each { |cb| cb.call(value, as) }
  end

  return true
end

#value ⇒ Object 



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# File 'lib/dharma/promise.rb', line 56

def value
  @mutex.synchronize do
    if @as
      @value
    else
      nil
    end
  end
end