class method · added in Ruby 3.4

Ractor.store_if_absent

[A] (::Symbol) { (nil) -> A } -> A

Ractor.store_if_absent(key){ init_block }

# File tmp/rubies/ruby-4.0.0/ractor.rb, line 513
def self.store_if_absent(sym)
  Primitive.attr! :use_block
  Primitive.ractor_local_value_store_if_absent(sym)
end

If the corresponding ractor-local value is not set, yields a value with init_block and stores the value in a thread-safe manner. This method returns the stored value.

Example

(1..10).map{
  Thread.new(it){|i|
    Ractor.store_if_absent(:s){ f(); i }
    #=> return stored value of key :s
  }
}.map(&:value).uniq.size #=> 1 and f() is called only once

Ruby version changes

3.4
- Ractor.store_if_absent(key){ init } is added to initialize ractor local variables in thread-safety. [Feature #20875]

See also .shareable_proc #<< .shareable_lambda #[] also in 4.1 · 3.4

‹ prev.shareable_proc next ›#<<