class Ractor - Documentation for Ruby 3.2

# class Ractor

`Ractor` is an Actor-model abstraction for Ruby that provides thread-safe parallel execution.

`Ractor.new` can make a new `Ractor`, and it will run in parallel.

    # The simplest ractor
    r = Ractor.new {puts "I am in Ractor!"}
    r.take # wait for it to finish
    # here "I am in Ractor!" would be printed

Ractors do not share usual objects, so the same kinds of thread-safety concerns such as data-race, race-conditions are not available on multi-ractor programming.

To achieve this, ractors severely limit object sharing between different ractors. For example, unlike threads, ractors can’t access each other’s objects, nor any objects through variables of the outer scope.

    a = 1
    r = Ractor.new {puts "I am in Ractor! a=#{a}"}
    # fails immediately with
    # ArgumentError (can not isolate a Proc because it accesses outer variables (a).)

On CRuby (the default implementation), Global Virtual Machine Lock (GVL) is held per ractor, so ractors are performed in parallel without locking each other.

Instead of accessing the shared state, the objects should be passed to and from ractors via sending and receiving objects as messages.

    a = 1
    r = Ractor.new do
      a_in_ractor = receive # receive blocks till somebody will pass message
      puts "I am in Ractor! a=#{a_in_ractor}"
    end
    r.send(a)  # pass it
    r.take
    # here "I am in Ractor! a=1" would be printed

There are two pairs of methods for sending/receiving messages:

- `Ractor#send` and `Ractor.receive` for when the sender knows the receiver (push);

- `Ractor.yield` and `Ractor#take` for when the receiver knows the sender (pull);

In addition to that, an argument to `Ractor.new` would be passed to block and available there as if received by `Ractor.receive`, and the last block value would be sent outside of the ractor as if sent by `Ractor.yield`.

A little demonstration on a classic ping-pong:

    server = Ractor.new do
      puts "Server starts: #{self.inspect}"
      puts "Server sends: ping"
      Ractor.yield 'ping'                       # The server doesn't know the receiver and sends to whoever interested
      received = Ractor.receive                 # The server doesn't know the sender and receives from whoever sent
      puts "Server received: #{received}"
    end

    client = Ractor.new(server) do |srv|        # The server is sent inside client, and available as srv
      puts "Client starts: #{self.inspect}"
      received = srv.take                       # The Client takes a message specifically from the server
      puts "Client received from " \
           "#{srv.inspect}: #{received}"
      puts "Client sends to " \
           "#{srv.inspect}: pong"
      srv.send 'pong'                           # The client sends a message specifically to the server
    end

    [client, server].each(&:take)               # Wait till they both finish

This will output:

    Server starts: #<Ractor:#2 test.rb:1 running>
    Server sends: ping
    Client starts: #<Ractor:#3 test.rb:8 running>
    Client received from #<Ractor:#2 rac.rb:1 blocking>: ping
    Client sends to #<Ractor:#2 rac.rb:1 blocking>: pong
    Server received: pong

It is said that `Ractor` receives messages via the incoming port, and sends them to the outgoing port. Either one can be disabled with `Ractor#close_incoming` and `Ractor#close_outgoing` respectively. If a ractor terminated, its ports will be closed automatically.

## Shareable and unshareable objects¶ ↑

When the object is sent to and from the ractor, it is important to understand whether the object is shareable or unshareable. Most of objects are unshareable objects.

Shareable objects are basically those which can be used by several threads without compromising thread-safety; e.g. immutable ones. `Ractor.shareable?` allows to check this, and `Ractor.make_shareable` tries to make object shareable if it is not.

    Ractor.shareable?(1)            #=> true -- numbers and other immutable basic values are
    Ractor.shareable?('foo')        #=> false, unless the string is frozen due to # freeze_string_literals: true
    Ractor.shareable?('foo'.freeze) #=> true

    ary = ['hello', 'world']
    ary.frozen?                 #=> false
    ary[0].frozen?              #=> false
    Ractor.make_shareable(ary)
    ary.frozen?                 #=> true
    ary[0].frozen?              #=> true
    ary[1].frozen?              #=> true

When a shareable object is sent (via `send` or `Ractor.yield`), no additional processing happens, and it just becomes usable by both ractors. When an unshareable object is sent, it can be either copied or moved. The first is the default, and it makes the object’s full copy by deep cloning of non-shareable parts of its structure.

    data = ['foo', 'bar'.freeze]
    r = Ractor.new do
      data2 = Ractor.receive
      puts "In ractor: #{data2.object_id}, #{data2[0].object_id}, #{data2[1].object_id}"
    end
    r.send(data)
    r.take
    puts "Outside  : #{data.object_id}, #{data[0].object_id}, #{data[1].object_id}"

This will output:

    In ractor: 340, 360, 320
    Outside  : 380, 400, 320

(Note that object id of both array and non-frozen string inside array have changed inside the ractor, showing it is different objects. But the second array’s element, which is a shareable frozen string, has the same object_id.)

Deep cloning of the objects may be slow, and sometimes impossible. Alternatively, `move: true` may be used on sending. This will move the object to the receiving ractor, making it inaccessible for a sending ractor.

    data = ['foo', 'bar']
    r = Ractor.new do
      data_in_ractor = Ractor.receive
      puts "In ractor: #{data_in_ractor.object_id}, #{data_in_ractor[0].object_id}"
    end
    r.send(data, move: true)
    r.take
    puts "Outside: moved? #{Ractor::MovedObject === data}"
    puts "Outside: #{data.inspect}"

This will output:

    In ractor: 100, 120
    Outside: moved? true
    test.rb:9:in `method_missing': can not send any methods to a moved object (Ractor::MovedError)

Notice that even `inspect` (and more basic methods like `__id__`) is inaccessible on a moved object.

Besides frozen objects, there are shareable objects. `Class` and `Module` objects are shareable so the Class/Module definitions are shared between ractors. `Ractor` objects are also shareable objects. All operations for the shareable mutable objects are thread-safe, so the thread-safety property will be kept. We can not define mutable shareable objects in Ruby, but C extensions can introduce them.

It is prohibited to access instance variables of mutable shareable objects (especially Modules and classes) from ractors other than main:

    class C
      class << self
        attr_accessor :tricky
      end
    end

    C.tricky = 'test'

    r = Ractor.new(C) do |cls|
      puts "I see #{cls}"
      puts "I can't see #{cls.tricky}"
    end
    r.take
    # I see C
    # can not access instance variables of classes/modules from non-main Ractors (RuntimeError)

Ractors can access constants if they are shareable. The main `Ractor` is the only one that can access non-shareable constants.

    GOOD = 'good'.freeze
    BAD = 'bad'

    r = Ractor.new do
      puts "GOOD=#{GOOD}"
      puts "BAD=#{BAD}"
    end
    r.take
    # GOOD=good
    # can not access non-shareable objects in constant Object::BAD by non-main Ractor. (NameError)

    # Consider the same C class from above

    r = Ractor.new do
      puts "I see #{C}"
      puts "I can't see #{C.tricky}"
    end
    r.take
    # I see C
    # can not access instance variables of classes/modules from non-main Ractors (RuntimeError)

See also the description of `# shareable_constant_value` pragma in Comments syntax explanation.

## Ractors vs threads¶ ↑

Each ractor creates its own thread. New threads can be created from inside ractor (and, on CRuby, sharing GVL with other threads of this ractor).

    r = Ractor.new do
      a = 1
      Thread.new {puts "Thread in ractor: a=#{a}"}.join
    end
    r.take
    # Here "Thread in ractor: a=1" will be printed

## Note on code examples¶ ↑

In examples below, sometimes we use the following method to wait till ractors that are not currently blocked will finish (or process till next blocking) method.

    def wait
      sleep(0.1)
    end

It is **only for demonstration purposes** and shouldn’t be used in a real code. Most of the times, just `take` is used to wait till ractor will finish.

## Reference¶ ↑

See Ractor design doc for more details.

### Public Class Methods

count() click to toggle source

Returns total count of Ractors currently running.

    Ractor.count                   #=> 1
    r = Ractor.new(name: 'example') { Ractor.yield(1) }
    Ractor.count                   #=> 2 (main + example ractor)
    r.take                         # wait for Ractor.yield(1)
    r.take                         # wait till r will finish
    Ractor.count                   #=> 1

    # File ractor.rb, line 291
    def self.count
      __builtin_cexpr! %q{
        ULONG2NUM(GET_VM()->ractor.cnt);
      }
    end

current() click to toggle source

Returns the currently executing `Ractor`.

    Ractor.current #=> #<Ractor:#1 running>

    # File ractor.rb, line 277
    def self.current
      __builtin_cexpr! %q{
        rb_ractor_self(rb_ec_ractor_ptr(ec));
      }
    end

main() click to toggle source

returns main ractor

    # File ractor.rb, line 837
    def self.main
      __builtin_cexpr! %q{
        rb_ractor_self(GET_VM()->ractor.main_ractor);
      }
    end

make_shareable(obj, copy: false) → shareable_obj click to toggle source

Make `obj` shareable between ractors.

`obj` and all the objects it refers to will be frozen, unless they are already shareable.

If `copy` keyword is `true`, the method will copy objects before freezing them This is safer option but it can take be slower.

Note that the specification and implementation of this method are not mature and may be changed in the future.

    obj = ['test']
    Ractor.shareable?(obj)     #=> false
    Ractor.make_shareable(obj) #=> ["test"]
    Ractor.shareable?(obj)     #=> true
    obj.frozen?                #=> true
    obj[0].frozen?             #=> true

    # Copy vs non-copy versions:
    obj1 = ['test']
    obj1s = Ractor.make_shareable(obj1)
    obj1.frozen?                        #=> true
    obj1s.object_id == obj1.object_id   #=> true
    obj2 = ['test']
    obj2s = Ractor.make_shareable(obj2, copy: true)
    obj2.frozen?                        #=> false
    obj2s.frozen?                       #=> true
    obj2s.object_id == obj2.object_id   #=> false
    obj2s[0].object_id == obj2[0].object_id #=> false

See also the “Shareable and unshareable objects” section in the `Ractor` class docs.

    # File ractor.rb, line 814
    def self.make_shareable obj, copy: false
      if copy
        __builtin_cexpr! %q{
          rb_ractor_make_shareable_copy(obj);
        }
      else
        __builtin_cexpr! %q{
          rb_ractor_make_shareable(obj);
        }
      end
    end

new(*args, name: nil) {|*args| block } → ractor click to toggle source

Create a new `Ractor` with args and a block.

A block (`Proc`) will be isolated (can’t access to outer variables). `self` inside the block will refer to the current `Ractor`.

    r = Ractor.new { puts "Hi, I am #{self.inspect}" }
    r.take
    # Prints "Hi, I am #<Ractor:#2 test.rb:1 running>"

`args` passed to the method would be propagated to block args by the same rules as objects passed through `send`/Ractor.receive: if `args` are not shareable, they will be copied (via deep cloning, which might be inefficient).

    arg = [1, 2, 3]
    puts "Passing: #{arg} (##{arg.object_id})"
    r = Ractor.new(arg) {|received_arg|
      puts "Received: #{received_arg} (##{received_arg.object_id})"
    }
    r.take
    # Prints:
    #   Passing: [1, 2, 3] (#280)
    #   Received: [1, 2, 3] (#300)

Ractor’s `name` can be set for debugging purposes:

    r = Ractor.new(name: 'my ractor') {}
    p r
    #=> #<Ractor:#3 my ractor test.rb:1 terminated>

    # File ractor.rb, line 262
    def self.new(*args, name: nil, &block)
      b = block # TODO: builtin bug
      raise ArgumentError, "must be called with a block" unless block
      if __builtin_cexpr!("RBOOL(ruby_single_main_ractor)")
        warn("Ractor is experimental, and the behavior may change in future versions of Ruby! " \
             "Also there are many implementation issues.", uplevel: 0, category: :experimental)
      end
      loc = caller_locations(1, 1).first
      loc = "#{loc.path}:#{loc.lineno}"
      __builtin_ractor_create(loc, name, args, b)
    end

receive → msg click to toggle source

Receive an incoming message from the current Ractor’s incoming port’s queue, which was sent there by `send`.

    r = Ractor.new do
      v1 = Ractor.receive
      puts "Received: #{v1}"
    end
    r.send('message1')
    r.take
    # Here will be printed: "Received: message1"

Alternatively, private instance method `receive` may be used:

    r = Ractor.new do
      v1 = receive
      puts "Received: #{v1}"
    end
    r.send('message1')
    r.take
    # Here will be printed: "Received: message1"

The method blocks if the queue is empty.

    r = Ractor.new do
      puts "Before first receive"
      v1 = Ractor.receive
      puts "Received: #{v1}"
      v2 = Ractor.receive
      puts "Received: #{v2}"
    end
    wait
    puts "Still not received"
    r.send('message1')
    wait
    puts "Still received only one"
    r.send('message2')
    r.take

Output:

    Before first receive
    Still not received
    Received: message1
    Still received only one
    Received: message2

If `close_incoming` was called on the ractor, the method raises `Ractor::ClosedError` if there are no more messages in incoming queue:

    Ractor.new do
      close_incoming
      receive
    end
    wait
    # in `receive': The incoming port is already closed => #<Ractor:#2 test.rb:1 running> (Ractor::ClosedError)

    # File ractor.rb, line 419
    def self.receive
      __builtin_cexpr! %q{
        ractor_receive(ec, rb_ec_ractor_ptr(ec))
      }
    end

Also aliased as: recv
receive_if {|msg| block } → msg click to toggle source

Receive only a specific message.

Instead of `Ractor.receive`, `Ractor.receive_if` can provide a pattern by a block and you can choose the receiving message.

    r = Ractor.new do
      p Ractor.receive_if{|msg| msg.match?(/foo/)} #=> "foo3"
      p Ractor.receive_if{|msg| msg.match?(/bar/)} #=> "bar1"
      p Ractor.receive_if{|msg| msg.match?(/baz/)} #=> "baz2"
    end
    r << "bar1"
    r << "baz2"
    r << "foo3"
    r.take

This will output:

    foo3
    bar1
    baz2

If the block returns a truthy value, the message will be removed from the incoming queue and returned. Otherwise, the message remains in the incoming queue and the following received messages are checked by the given block.

If there are no messages left in the incoming queue, the method will block until new messages arrive.

If the block is escaped by break/return/exception/throw, the message is removed from the incoming queue as if a truthy value had been returned.

    r = Ractor.new do
      val = Ractor.receive_if{|msg| msg.is_a?(Array)}
      puts "Received successfully: #{val}"
    end

    r.send(1)
    r.send('test')
    wait
    puts "2 non-matching sent, nothing received"
    r.send([1, 2, 3])
    wait

Prints:

    2 non-matching sent, nothing received
    Received successfully: [1, 2, 3]

Note that you can not call receive/receive_if in the given block recursively. It means that you should not do any tasks in the block.

    Ractor.current << true
    Ractor.receive_if{|msg| Ractor.receive}
    #=> `receive': can not call receive/receive_if recursively (Ractor::Error)

    # File ractor.rb, line 497
    def self.receive_if &b
      Primitive.ractor_receive_if b
    end

recv()
Alias for: receive
select(*ractors, [yield_value:, move: false]) → [ractor or symbol, obj] click to toggle source

Waits for the first ractor to have something in its outgoing port, reads from this ractor, and returns that ractor and the object received.

    r1 = Ractor.new {Ractor.yield 'from 1'}
    r2 = Ractor.new {Ractor.yield 'from 2'}

    r, obj = Ractor.select(r1, r2)

    puts "received #{obj.inspect} from #{r.inspect}"
    # Prints: received "from 1" from #<Ractor:#2 test.rb:1 running>

If one of the given ractors is the current ractor, and it would be selected, `r` will contain `:receive` symbol instead of the ractor object.

    r1 = Ractor.new(Ractor.current) do |main|
      main.send 'to main'
      Ractor.yield 'from 1'
    end
    r2 = Ractor.new do
      Ractor.yield 'from 2'
    end

    r, obj = Ractor.select(r1, r2, Ractor.current)
    puts "received #{obj.inspect} from #{r.inspect}"
    # Prints: received "to main" from :receive

If `yield_value` is provided, that value may be yielded if another `Ractor` is calling `take`. In this case, the pair `[:yield, nil]` would be returned:

    r1 = Ractor.new(Ractor.current) do |main|
      puts "Received from main: #{main.take}"
    end

    puts "Trying to select"
    r, obj = Ractor.select(r1, Ractor.current, yield_value: 123)
    wait
    puts "Received #{obj.inspect} from #{r.inspect}"

This will print:

    Trying to select
    Received from main: 123
    Received nil from :yield

`move` boolean flag defines whether yielded value should be copied (default) or moved.

    # File ractor.rb, line 346
    def self.select(*ractors, yield_value: yield_unspecified = true, move: false)
      raise ArgumentError, 'specify at least one ractor or `yield_value`' if yield_unspecified && ractors.empty?

      __builtin_cstmt! %q{
        const VALUE *rs = RARRAY_CONST_PTR_TRANSIENT(ractors);
        VALUE rv;
        VALUE v = ractor_select(ec, rs, RARRAY_LENINT(ractors),
                                yield_unspecified == Qtrue ? Qundef : yield_value,
                                (bool)RTEST(move) ? true : false, &rv);
        return rb_ary_new_from_args(2, rv, v);
      }
    end

shareable?(obj) → true | false click to toggle source

Checks if the object is shareable by ractors.

    Ractor.shareable?(1)            #=> true -- numbers and other immutable basic values are frozen
    Ractor.shareable?('foo')        #=> false, unless the string is frozen due to # freeze_string_literals: true
    Ractor.shareable?('foo'.freeze) #=> true

See also the “Shareable and unshareable objects” section in the `Ractor` class docs.

    # File ractor.rb, line 773
    def self.shareable? obj
      __builtin_cexpr! %q{
        RBOOL(rb_ractor_shareable_p(obj));
      }
    end

yield(msg, move: false) → nil click to toggle source

Send a message to the current ractor’s outgoing port to be consumed by `take`.

    r = Ractor.new {Ractor.yield 'Hello from ractor'}
    puts r.take
    # Prints: "Hello from ractor"

The method is blocking, and will return only when somebody consumes the sent message.

    r = Ractor.new do
      Ractor.yield 'Hello from ractor'
      puts "Ractor: after yield"
    end
    wait
    puts "Still not taken"
    puts r.take

This will print:

    Still not taken
    Hello from ractor
    Ractor: after yield

If the outgoing port was closed with `close_outgoing`, the method will raise:

    r = Ractor.new do
      close_outgoing
      Ractor.yield 'Hello from ractor'
    end
    wait
    # `yield': The outgoing-port is already closed (Ractor::ClosedError)

The meaning of `move` argument is the same as for `send`.

    # File ractor.rb, line 630
    def self.yield(obj, move: false)
      __builtin_cexpr! %q{
        ractor_yield(ec, rb_ec_ractor_ptr(ec), obj, move)
      }
    end

### Public Instance Methods

<<(obj, move: false)
Alias for: send
[](sym) click to toggle source

get a value from ractor-local storage

    # File ractor.rb, line 827
    def [](sym)
      Primitive.ractor_local_value(sym)
    end

[]=(sym, val) click to toggle source

set a value in ractor-local storage

    # File ractor.rb, line 832
    def []=(sym, val)
      Primitive.ractor_local_value_set(sym, val)
    end

close_incoming → true | false click to toggle source

Closes the incoming port and returns its previous state. All further attempts to `Ractor.receive` in the ractor, and `send` to the ractor will fail with `Ractor::ClosedError`.

    r = Ractor.new {sleep(500)}
    r.close_incoming  #=> false
    r.close_incoming  #=> true
    r.send('test')
    # Ractor::ClosedError (The incoming-port is already closed)

    # File ractor.rb, line 737
    def close_incoming
      __builtin_cexpr! %q{
        ractor_close_incoming(ec, RACTOR_PTR(self));
      }
    end

close_outgoing → true | false click to toggle source

Closes the outgoing port and returns its previous state. All further attempts to `Ractor.yield` in the ractor, and `take` from the ractor will fail with `Ractor::ClosedError`.

    r = Ractor.new {sleep(500)}
    r.close_outgoing  #=> false
    r.close_outgoing  #=> true
    r.take
    # Ractor::ClosedError (The outgoing-port is already closed)

    # File ractor.rb, line 756
    def close_outgoing
      __builtin_cexpr! %q{
        ractor_close_outgoing(ec, RACTOR_PTR(self));
      }
    end

inspect() click to toggle source

    # File ractor.rb, line 703
    def inspect
      loc  = __builtin_cexpr! %q{ RACTOR_PTR(self)->loc }
      name = __builtin_cexpr! %q{ RACTOR_PTR(self)->name }
      id   = __builtin_cexpr! %q{ UINT2NUM(rb_ractor_id(RACTOR_PTR(self))) }
      status = __builtin_cexpr! %q{
        rb_str_new2(ractor_status_str(RACTOR_PTR(self)->status_))
      }
      "#<Ractor:##{id}#{name ? ' '+name : ''}#{loc ? " " + loc : ''} #{status}>"
    end

Also aliased as: to_s
name() click to toggle source

The name set in `Ractor.new`, or `nil`.

    # File ractor.rb, line 716
    def name
      __builtin_cexpr! %q{RACTOR_PTR(self)->name}
    end

recv()
Alias for: receive
send(msg, move: false) → self click to toggle source

Send a message to a Ractor’s incoming queue to be consumed by `Ractor.receive`.

    r = Ractor.new do
      value = Ractor.receive
      puts "Received #{value}"
    end
    r.send 'message'
    # Prints: "Received: message"

The method is non-blocking (will return immediately even if the ractor is not ready to receive anything):

    r = Ractor.new {sleep(5)}
    r.send('test')
    puts "Sent successfully"
    # Prints: "Sent successfully" immediately

Attempt to send to ractor which already finished its execution will raise `Ractor::ClosedError`.

    r = Ractor.new {}
    r.take
    p r
    # "#<Ractor:#6 (irb):23 terminated>"
    r.send('test')
    # Ractor::ClosedError (The incoming-port is already closed)

If `close_incoming` was called on the ractor, the method also raises `Ractor::ClosedError`.

    r =  Ractor.new do
      sleep(500)
      receive
    end
    r.close_incoming
    r.send('test')
    # Ractor::ClosedError (The incoming-port is already closed)
    # The error would be raised immediately, not when ractor will try to receive

If the `obj` is unshareable, by default it would be copied into ractor by deep cloning. If the `move: true` is passed, object is moved into ractor and becomes inaccessible to sender.

    r = Ractor.new {puts "Received: #{receive}"}
    msg = 'message'
    r.send(msg, move: true)
    r.take
    p msg

This prints:

    Received: message
    in `p': undefined method `inspect' for #<Ractor::MovedObject:0x000055c99b9b69b8>

All references to the object and its parts will become invalid in sender.

    r = Ractor.new {puts "Received: #{receive}"}
    s = 'message'
    ary = [s]
    copy = ary.dup
    r.send(ary, move: true)

    s.inspect
    # Ractor::MovedError (can not send any methods to a moved object)
    ary.class
    # Ractor::MovedError (can not send any methods to a moved object)
    copy.class
    # => Array, it is different object
    copy[0].inspect
    # Ractor::MovedError (can not send any methods to a moved object)
    # ...but its item was still a reference to `s`, which was moved

If the object was shareable, `move: true` has no effect on it:

    r = Ractor.new {puts "Received: #{receive}"}
    s = 'message'.freeze
    r.send(s, move: true)
    s.inspect #=> "message", still available

    # File ractor.rb, line 586
    def send(obj, move: false)
      __builtin_cexpr! %q{
        ractor_send(ec, RACTOR_PTR(self), obj, move)
      }
    end

Also aliased as: <<
take → msg click to toggle source

Take a message from ractor’s outgoing port, which was put there by `Ractor.yield` or at ractor’s finalization.

    r = Ractor.new do
      Ractor.yield 'explicit yield'
      'last value'
    end
    puts r.take #=> 'explicit yield'
    puts r.take #=> 'last value'
    puts r.take # Ractor::ClosedError (The outgoing-port is already closed)

The fact that the last value is also put to outgoing port means that `take` can be used as some analog of `Thread#join` (“just wait till ractor finishes”), but don’t forget it will raise if somebody had already consumed everything ractor have produced.

If the outgoing port was closed with `close_outgoing`, the method will raise `Ractor::ClosedError`.

    r = Ractor.new do
      sleep(500)
      Ractor.yield 'Hello from ractor'
    end
    r.close_outgoing
    r.take
    # Ractor::ClosedError (The outgoing-port is already closed)
    # The error would be raised immediately, not when ractor will try to receive

If an uncaught exception is raised in the `Ractor`, it is propagated on take as a `Ractor::RemoteError`.

    r = Ractor.new {raise "Something weird happened"}

    begin
      r.take
    rescue => e
      p e              #  => #<Ractor::RemoteError: thrown by remote Ractor.>
      p e.ractor == r  # => true
      p e.cause        # => #<RuntimeError: Something weird happened>
    end

`Ractor::ClosedError` is a descendant of `StopIteration`, so the closing of the ractor will break the loops without propagating the error:

    r = Ractor.new do
      3.times {|i| Ractor.yield "message #{i}"}
      "finishing"
    end

    loop {puts "Received: " + r.take}
    puts "Continue successfully"

This will print:

    Received: message 0
    Received: message 1
    Received: message 2
    Received: finishing
    Continue successfully

    # File ractor.rb, line 697
    def take
      __builtin_cexpr! %q{
        ractor_take(ec, RACTOR_PTR(self))
      }
    end

to_s()
Alias for: inspect

### Private Instance Methods

receive() click to toggle source

same as `Ractor.receive`

    # File ractor.rb, line 430
            def receive
      __builtin_cexpr! %q{
        ractor_receive(ec, rb_ec_ractor_ptr(ec))
      }
    end

Also aliased as: recv
receive_if(&b) click to toggle source

    # File ractor.rb, line 501
            def receive_if &b
      Primitive.ractor_receive_if b
    end