Class: EventMachine::Q::DeferredPromise

Inherits:
Promise
  • Object
show all
Defined in:
lib/em-promise/q.rb

Overview

A new promise instance is created when a deferred instance is created and can be retrieved by calling deferred.promise

Instance Method Summary collapse

Constructor Details

#initialize(defer) ⇒ DeferredPromise

Returns a new instance of DeferredPromise.

Raises:

  • (ArgumentError) 


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# File 'lib/em-promise/q.rb', line 23

def initialize(defer)
	raise ArgumentError unless defer.is_a?(Deferred)
	super()
	
	@defer = defer
end

Instance Method Details

#then(callback = nil, errback = nil, &blk) ⇒ Promise

regardless of when the promise was or will be resolved / rejected, calls one of the success or error callbacks asynchronously as soon as the result is available. The callbacks are called with a single argument, the result or rejection reason.

Parameters:

  • callbacks (Proc, Proc, &blk) —

    success, error, success_block

Returns:

  • (Promise) —

    Returns an unresolved promise for chaining



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# File 'lib/em-promise/q.rb', line 37

def then(callback = nil, errback = nil, &blk)
	result = Q.defer
	
	callback ||= blk
	
	wrappedCallback = proc { |val|
		begin
			result.resolve(callback.nil? ? val : callback.call(val))
		rescue => e
			warn "\nUnhandled exception: #{e.message}\n#{e.backtrace.join("\n")}\n"
			result.reject(e);
		end
	}
	
	wrappedErrback = proc { |reason|
		begin
			result.resolve(errback.nil? ? Q.reject(reason) : errback.call(reason))
		rescue => e
			warn "Unhandled exception: #{e.message}\n#{e.backtrace.join("\n")}\n"
			result.reject(e);
		end
	}
	
	#
	# Schedule as we are touching shared state
	#	Everything else is locally scoped
	#
	EM.schedule do
		pending_array = pending
		
		if pending_array.nil?
			value.then(wrappedCallback, wrappedErrback)
		else
			pending_array << [wrappedCallback, wrappedErrback]
		end
	end
	
	result.promise
end