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Class: Concurrent::AtomicReference

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Subclasses:
ThreadSafe::Util::Striped64::Cell
Inherits: Concurrent::AtomicReferenceImplementation
Defined in: lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb

Overview

An object reference that may be updated atomically. All read and write operations have java volatile semantic.

## Thread-safe Variable Classes

Each of the thread-safe variable classes is designed to solve a different problem. In general:

  • *Agent:* Shared, mutable variable providing independent, uncoordinated, asynchronous change of individual values. Best used when the value will undergo frequent, complex updates. Suitable when the result of an update does not need to be known immediately.

  • *Atom:* Shared, mutable variable providing independent, uncoordinated, synchronous change of individual values. Best used when the value will undergo frequent reads but only occasional, though complex, updates. Suitable when the result of an update must be known immediately.

  • *AtomicReference:* A simple object reference that can be updated atomically. Updates are synchronous but fast. Best used when updates a simple set operations. Not suitable when updates are complex. AtomicBoolean and AtomicFixnum are similar but optimized for the given data type.

  • *Exchanger:* Shared, stateless synchronization point. Used when two or more threads need to exchange data. The threads will pair then block on each other until the exchange is complete.

  • *MVar:* Shared synchronization point. Used when one thread must give a value to another, which must take the value. The threads will block on each other until the exchange is complete.

  • *ThreadLocalVar:* Shared, mutable, isolated variable which holds a different value for each thread which has access. Often used as an instance variable in objects which must maintain different state for different threads.

  • *TVar:* Shared, mutable variables which provide coordinated, synchronous, change of many stated. Used when multiple value must change together, in an all-or-nothing transaction.

See Also:

Class Method Summary

Instance Method Summary

Constructor Details

.new(value = nil)

Parameters:

  • value (Object) (defaults to: nil) —

    The initial value.

[ GitHub ] 

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end


  







Instance Method Details



  

    #compare_and_set(old_value, new_value)  ⇒ Boolean 
    Also known as: #cas
  



  

    

Atomically sets the value to the given updated value if the current value == the expected value.



that the actual value was not equal to the expected value.


  





  
Parameters:


    
  
  • 
    old_value
    (Object)
—    
    

    the expected value
    

    
  
    • 
  
  • 
    new_value
    (Object)
—    
    

    the new value
    

    
  
    • 



Returns:


    
  
  • 
    (Boolean)
—    
    

    true if successful. A false return indicates
    

    
  
    • 





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end


  








  

    #get  ⇒ Object 
  



  

    

Gets the current value.


  





  
Returns:


    
  
  • 
    (Object)
—    
    

    the current value
    

    
  
    • 





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end


  








  

    #get_and_set(new_value)  ⇒ Object 
  



  

    

Atomically sets to the given value and returns the old value.


  





  
Parameters:


    
  
  • 
    new_value
    (Object)
—    
    

    the new value
    

    
  
    • 



Returns:





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end


  








  

    #inspect  
  



  

    

Alias for #to_s.


  



  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 133



alias_method :inspect, :to_s


  








  

    #set(new_value)  ⇒ Object 
  



  

    

Sets to the given value.


  





  
Parameters:


    
  
  • 
    new_value
    (Object)
—    
    

    the new value
    

    
  
    • 



Returns:





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end


  








  

    #to_s  ⇒ String 
    Also known as: #inspect
  



  

    
  





  
Returns:


    
  
  • 
    (String)
—    
    

    Short string representation.
    

    
  
    • 





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 129



def to_s
  format '%s value:%s>', super[0..-2], get
end


  








  

    #try_update {|Object| ... } ⇒ Object 
  



  

    
  

    Note:
    


This method was altered to avoid raising an exception by default. Instead, this method now returns nil in case of failure. For more info, please see: github.com/ruby-concurrency/concurrent-ruby/pull/336



  




Pass the current value to the given block, replacing it with the block’s result. Return nil if the update fails.


  





  
Yields:


    
  
  • 
    (Object)
—    
    

    Calculate a new value for the atomic reference using given (old) value
    

    
  
    • 



Yield Parameters:


    
  
  • 
    old_value
    (Object)
—    
    

    the starting value of the atomic reference
    

    
  
    • 



Returns:


    
  
  • 
    (Object)
—    
    

    the new value, or nil if update failed
    

    
  
    • 





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end


  








  

    #try_update! {|Object| ... } ⇒ Object 
  



  

    
  

    Note:
    


This behavior mimics the behavior of the original #try_update API. The reason this was changed was to avoid raising exceptions (which are inherently slow) by default. For more info: github.com/ruby-concurrency/concurrent-ruby/pull/336



  




Pass the current value to the given block, replacing it with the block’s result. Raise an exception if the update fails.


  





  
Yields:


    
  
  • 
    (Object)
—    
    

    Calculate a new value for the atomic reference using given (old) value
    

    
  
    • 



Yield Parameters:


    
  
  • 
    old_value
    (Object)
—    
    

    the starting value of the atomic reference
    

    
  
    • 



Returns:



Raises:





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end


  








  

    #update {|Object| ... } ⇒ Object 
  



  

    

Pass the current value to the given block, replacing it with the block’s result. May retry if the value changes during the block’s execution.


  





  
Yields:


    
  
  • 
    (Object)
—    
    

    Calculate a new value for the atomic reference using given (old) value
    

    
  
    • 



Yield Parameters:


    
  
  • 
    old_value
    (Object)
—    
    

    the starting value of the atomic reference
    

    
  
    • 



Returns:





  [ GitHub ]


  

  


# File 'lib/concurrent-ruby/concurrent/atomic/atomic_reference.rb', line 126



class AtomicReference < AtomicReferenceImplementation

  # @return [String] Short string representation.
  def to_s
    format '%s value:%s>', super[0..-2], get
  end

  alias_method :inspect, :to_s
end