Class: Brainguy::SubscriptionScope

Inherits:
Emitter
  • Object
show all
Defined in:
lib/brainguy/subscription_scope.rb

Overview

A scope for subscriptions with a limited lifetime.

Sometimes it's useful to have a set of subscriptions with a limited lifetime. For instance, a set of observers which are only valid over the course of a single method call. This class wraps an existing Emitter, and exposes the same API. But when a client sends the #close message, all listeners subscribed through this object will be immediately unsubscribed.

Constant Summary

Constants inherited from Emitter

Emitter::DEFAULT_NOTIFIER

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Emitter

#detach, #emit, new_from_existing, #subscriptions, #with_subscription_scope

Constructor Details

#initialize(subscription_set) ⇒ SubscriptionScope

Returns a new instance of SubscriptionScope.

Parameters:

  • subscription_set (Emitter) —

    the subscription set to wrap


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# File 'lib/brainguy/subscription_scope.rb', line 28

def initialize(subscription_set)
  super(subscription_set)
  @subscriptions = []
end

Class Method Details

.open(subscription_set) {|SubscriptionScope| ... } ⇒ Object

Create a new scope and yield it to the block. Closes the scope (unsubscribing any listeners attached using the scope) at the end of block execution

Parameters:

  • subscription_set (Emitter) —

    the subscription set to wrap

Yields:


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# File 'lib/brainguy/subscription_scope.rb', line 20

def self.open(subscription_set)
  scope = self.new(subscription_set)
  yield scope
ensure
  scope.close
end

Instance Method Details

#attach ⇒ Subscription

Attach a new object to listen for events. A listener is expected to be call-able, and it will receive the #call message with an Event each time one is emitted.

Parameters:

  • new_listener (:call)

Returns:

  • (Subscription) —

    a subscription object which can be used to cancel the subscription.


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# File 'lib/brainguy/subscription_scope.rb', line 41

def attach(*)
  super.tap do |subscription|
    @subscriptions << subscription
  end
end

#close ⇒ void

This method returns an undefined value.

Detach every listener that was attached via this scope.


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# File 'lib/brainguy/subscription_scope.rb', line 49

def close
  @subscriptions.each(&:cancel)
  @subscriptions.clear
end

#on(name, &block) ⇒ Subscription #on(handlers) ⇒ Subscription

Attach blocks of code to handle specific named events.

Overloads:

  • #on(name, &block) ⇒ Subscription

    Attach a block to be called for a specific event. The block will be called with the event arguments (not the event object).

    Parameters:

    • name (Symbol)
    • block (Proc) —

      what to do when the event is emitted

  • #on(handlers) ⇒ Subscription

    Attach multiple event-specific handlers at once.

    Parameters:

    • handlers (Hash{Symbol => [:call]}) —

      a map of event names to callable handlers.

Returns:

  • (Subscription) —

    a subscription object which can be used to cancel the subscription.


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# File 'lib/brainguy/subscription_scope.rb', line 34

def on(*)
  super.tap do |subscription|
    @subscriptions << subscription
  end
end