class Concurrent::FiberLocalVar

v.value #=> 14
end.resume
v.value #=> 2
v.value = 2
v.value #=> 14
Fiber.new do
end.resume
v.value #=> 1
v.value = 1
v.value #=> 14
Fiber.new do
v = FiberLocalVar.new(14)
@example
v.value #=> 2
v.value = 2
v.value #=> 14
v = FiberLocalVar.new(14)
@example
`FiberLocalVar` automatically removes the mapping for each fiber once the ‘FiberLocalVar` instance is GC’d.
* Ruby’s built-in fiber-local variables leak forever the value set on each fiber (unless set to nil explicitly).
‘FiberLocalVar` has no such issue and it is fine to create many of them.
so it’s only OK to create a small amount of them.
* Each Ruby’s built-in fiber-local variable leaks some memory forever (it’s a Symbol held forever on the fiber),
* ‘FiberLocalVar` has its own identity, it doesn’t need a Symbol.
but with these major advantages:
This is similar to Ruby’s built-in fiber-local variables (‘Thread.current`),
the current fiber will ever see that change.
Each variable may have a default value, but when you modify the variable only
A `FiberLocalVar` is a variable where the value is different for each fiber.

def bind(value)

Returns:
  • (Object) - the value

Other tags:
    Yield: - the operation to be performed with the bound variable

Parameters:
  • value (Object) -- the value to bind 
def bind(value)
  if block_given?
    old_value = self.value
    self.value = value
    begin
      yield
    ensure
      self.value = old_value
    end
  end
end

def default

@!visibility private 
def default
  if @default_block
    self.value = @default_block.call
  else
    @default
  end
end

def initialize(default = nil, &default_block)

Parameters:
  • default_block (Proc) -- Optional block that gets called to obtain the
  • default (Object) -- the default value when otherwise unset 
def initialize(default = nil, &default_block)
  if default && block_given?
    raise ArgumentError, "Cannot use both value and block as default value"
  end
  if block_given?
    @default_block = default_block
    @default = nil
  else
    @default_block = nil
    @default = default
  end
  @index = LOCALS.next_index(self)
end

def value

Returns:
  • (Object) - the current value 
def value
  LOCALS.fetch(@index) { default }
end

def value=(value)

Returns:
  • (Object) - the new value

Parameters:
  • value (Object) -- the value to set 
def value=(value)
  LOCALS.set(@index, value)
end