Module: Eventbox::Boxable

Included in:
Eventbox, Timer
Defined in:
lib/eventbox/boxable.rb

Overview

Extend modules with Eventbox method creation functions

This works like so:

module MyHelpers
  extend Eventbox::Boxable
  sync_call def hello
    puts "hello!"
  end
end

class MyBox < Eventbox
  include MyHelpers
end

MyBox.new.hello   # prints "hello!"

Instance Method Summary collapse

Instance Method Details

#action(name, &block) ⇒ Object (private)

Define a private method for asynchronous execution.

The call to the action method returns immediately after starting a new action. It returns an Action object. By default each call to an action method spawns a new thread which executes the code of the action definition. Alternatively a threadpool can be assigned by Eventbox.with_options.

All method arguments are passed through the Sanitizer.

Actions can return state changes or objects to the event loop by calls to methods created by #async_call, #sync_call or #yield_call or through calling Eventbox#async_proc, Eventbox#sync_proc or Eventbox#yield_proc objects. To avoid unsafe shared objects, an action has it's own set of local variables or instance variables. It doesn't have access to variables defined by other methods.

The Action object can be used to interrupt the program execution by an exception. See Action for further information. If the action method accepts one more argument than given to the action call, it is set to corresponding Action instance:

async_call def init
  do_something("value1")
end
action def do_something(str, action)
  str              # => "value1"
  action.current?  # => true
  # `action' can be passed to event scope or external scope,
  # in order to send a signals per Action#raise
end

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# File 'lib/eventbox/boxable.rb', line 198

def action(name, &block)
  unbound_method = self.instance_method(name)
  with_block_or_def(name, block) do |*args, &cb|
    raise InvalidAccess, "action must not be called with a block" if cb

    gc_actions = self.class.eventbox_options[:gc_actions]
    sandbox = self.class.allocate
    sandbox.instance_variable_set(:@__event_loop__, @__event_loop__)
    sandbox.instance_variable_set(:@__eventbox__, gc_actions ? WeakRef.new(self) : self)
    meth = unbound_method.bind(sandbox)

    if @__event_loop__.event_scope?
      args = Sanitizer.sanitize_values(args, @__event_loop__, nil)
    end
    # Start a new action thread and return an Action instance
    @__event_loop__.start_action(meth, name, args)
  end
  private name
  name
end

#async_call(name, &block) ⇒ Object (private)

Define a threadsafe method for asynchronous (fire-and-forget) calls.

The created method can be safely called from any thread. All method arguments are passed through the Sanitizer. Arguments prefixed by a € sign are automatically passed as WrappedObject.

The method itself might not do any blocking calls or expensive computations - this would impair responsiveness of the Eventbox instance. Instead use #action in these cases.

In contrast to #sync_call it's not possible to call external blocks or proc objects from #async_call methods.

The method always returns self to the caller.


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# File 'lib/eventbox/boxable.rb', line 47

def async_call(name, &block)
  unbound_method = self.instance_method(name)
  wrapper = ArgumentWrapper.build(unbound_method, name)
  with_block_or_def(name, block) do |*args, &cb|
    if @__event_loop__.event_scope?
      # Use the correct method within the class hierarchy, instead of just self.send(*args).
      # Otherwise super() would start an infinite recursion.
      unbound_method.bind(eventbox).call(*args, &cb)
    else
      @__event_loop__.async_call(eventbox, name, args, cb, wrapper)
    end
    self
  end
end

#attr_accessor(name) ⇒ Object (private)

Threadsafe read and write access to instance variables.

Attention: Be careful with read-modify-write operations - they are not atomic but are executed as two independent operations.

This will lose counter increments, since `counter` is incremented in a non-atomic manner:

attr_accessor :counter
async_call def start
  10.times { do_something }
end
action def do_something
  self.counter += 1
end

Instead don't use accessors but do increments within one method call like so:

async_call def start
  10.times { do_something }
end
action def do_something
  increment 1
end
async_call def increment(by)
  @counter += by
end

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# File 'lib/eventbox/boxable.rb', line 167

def attr_accessor(name)
  attr_reader name
  attr_writer name
end

#attr_reader(name) ⇒ Object (private)

Threadsafe read access to instance variables.


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# File 'lib/eventbox/boxable.rb', line 138

def attr_reader(name)
  sync_call(define_method("#{name}") do
    instance_variable_get("@#{name}")
  end)
end

#attr_writer(name) ⇒ Object (private)

Threadsafe write access to instance variables.


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# File 'lib/eventbox/boxable.rb', line 131

def attr_writer(name)
  async_call(define_method("#{name}=") do |value|
    instance_variable_set("@#{name}", value)
  end)
end

#sync_call(name, &block) ⇒ Object (private)

Define a method for synchronous calls.

The created method can be safely called from any thread. It is simular to #async_call, but the method waits until the method body is executed and returns its return value. Since all processing within the event scope of an Eventbox instance must not involve blocking operations, sync calls can only return immediate values. For deferred results use #yield_call instead.

It's possible to call external blocks or proc objects from #sync_call methods. Blocks are executed by the same thread that calls the #sync_call method to that time.

All method arguments as well as the result value are passed through the Sanitizer. Arguments prefixed by a € sign are automatically passed as WrappedObject.

The method itself might not do any blocking calls or expensive computations - this would impair responsiveness of the Eventbox instance. Instead use #action in these cases.


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# File 'lib/eventbox/boxable.rb', line 77

def sync_call(name, &block)
  unbound_method = self.instance_method(name)
  wrapper = ArgumentWrapper.build(unbound_method, name)
  with_block_or_def(name, block) do |*args, &cb|
    if @__event_loop__.event_scope?
      unbound_method.bind(eventbox).call(*args, &cb)
    else
      answer_queue = Queue.new
      sel = @__event_loop__.sync_call(eventbox, name, args, cb, answer_queue, wrapper)
      @__event_loop__.callback_loop(answer_queue, sel)
    end
  end
end

#yield_call(name, &block) ⇒ Object (private)

Define a method for calls with deferred result.

This call type is simular to #sync_call, however it's not the result of the method that is returned. Instead the method is called with one additional argument in the event scope, which is used to yield a result value or raise an exception. In contrast to a return statement, the execution of the method continues after yielding a result.

The result value can be yielded within the called method, but it can also be stored and called by any other event scope or external method, leading to a deferred method return. The external thread calling this method is suspended until a result is yielded. However the Eventbox object keeps responsive to calls from other threads.

The created method can be safely called from any thread. If yield methods are called in the event scope, they must get a Proc object as the last argument. It is called when a result was yielded.

It's possible to call external blocks or proc objects from #yield_call methods up to the point when the result was yielded. Blocks are executed by the same thread that calls the #yield_call method to that time.

All method arguments as well as the result value are passed through the Sanitizer. Arguments prefixed by a € sign are automatically passed as WrappedObject.

The method itself as well as the Proc object might not do any blocking calls or expensive computations - this would impair responsiveness of the Eventbox instance. Instead use #action in these cases.


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# File 'lib/eventbox/boxable.rb', line 113

def yield_call(name, &block)
  unbound_method = self.instance_method(name)
  wrapper = ArgumentWrapper.build(unbound_method, name)
  with_block_or_def(name, block) do |*args, **kwargs, &cb|
    if @__event_loop__.event_scope?
      @__event_loop__.safe_yield_result(args, name)
      args << kwargs unless kwargs.empty?
      unbound_method.bind(eventbox).call(*args, &cb)
      self
    else
      answer_queue = Queue.new
      sel = @__event_loop__.yield_call(eventbox, name, args, kwargs, cb, answer_queue, wrapper)
      @__event_loop__.callback_loop(answer_queue, sel)
    end
  end
end