Class: Libuv::Q::Deferred

Inherits:
Object show all
Includes:
Libuv::Q
Defined in:
lib/libuv/q.rb

Overview

The purpose of the deferred object is to expose the associated Promise instance as well as APIs that can be used for signalling the successful or unsuccessful completion of a task.

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Libuv::Q

all, any, defer, finally, reject

Constructor Details

#initialize(loop) ⇒ Deferred

Returns a new instance of Deferred.



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# File 'lib/libuv/q.rb', line 222

def initialize(loop)
    super()
    
    @pending = []
    @value = nil
    @loop = loop
end

Instance Attribute Details

#pending ⇒ Object (readonly)

Returns the value of attribute pending.



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# File 'lib/libuv/q.rb', line 230

def pending
  @pending
end

#value ⇒ Object (readonly)

Returns the value of attribute value.



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# File 'lib/libuv/q.rb', line 230

def value
  @value
end

Instance Method Details

#inspect ⇒ Object

Overwrite to prevent inspecting errors hanging the VM



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# File 'lib/libuv/q.rb', line 292

def inspect
    if @pending.nil?
        "#<#{self.class}:0x#{self.__id__.to_s(16)} @loop=#{@loop.inspect} @value=#{@value.inspect}>"
    else
          "#<#{self.class}:0x#{self.__id__.to_s(16)} @loop=#{@loop.inspect} @pending.count=#{@pending.length}>"
    end
end

#notify(*args) ⇒ Object

Provides an asynchronous callback mechanism

Parameters:

  • data (*Object) —

    you would like to send down the promise chain.



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# File 'lib/libuv/q.rb', line 274

def notify(*args)
    @loop.schedule do     # just in case we are on a different event loop

        if @pending && @pending.length > 0
            callbacks = @pending
            @loop.next_tick do
                callbacks.each do |callback|
                    callback[2].call(*args)
                end
            end
        end
    end
end

#promise ⇒ Object

Creates a promise object associated with this deferred



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# File 'lib/libuv/q.rb', line 265

def promise
    @promise ||= DeferredPromise.new(@loop, self)
    @promise # Should only ever be one per deferred

end

#reject(reason = nil) ⇒ Object

rejects the derived promise with the reason. This is equivalent to resolving it with a rejection constructed via Q.reject.

Parameters:

  • reason (Object) (defaults to: nil) —

    constant, message, exception or an object representing the rejection reason.



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# File 'lib/libuv/q.rb', line 258

def reject(reason = nil)
    resolve(Q.reject(@loop, reason))
end

#resolve(val = nil) ⇒ Object

resolves the derived promise with the value. If the value is a rejection constructed via Q.reject, the promise will be rejected instead.

Parameters:

  • val (Object) (defaults to: nil) —

    constant, message or an object representing the result.



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# File 'lib/libuv/q.rb', line 237

def resolve(val = nil)
    @loop.schedule do
        if not @pending.nil?
            callbacks = @pending
            @pending = nil
            @value = ref(@loop, val)
            
            if callbacks.length > 0
                callbacks.each do |callback|
                    @value.then(callback[0], callback[1], callback[2])
                end
            end
        end
    end
end

#resolved? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/libuv/q.rb', line 287

def resolved?
    @pending.nil?
end