Method: Redis::Commands::Transactions#watch

Defined in:
lib/redis/commands/transactions.rb

#watch(*keys) ⇒ Object, String

Watch the given keys to determine execution of the MULTI/EXEC block.

Using a block is optional, but is necessary for thread-safety.

An ‘#unwatch` is automatically issued if an exception is raised within the block that is a subclass of StandardError and is not a ConnectionError.

Examples:

With a block

redis.watch("key") do
  if redis.get("key") == "some value"
    redis.multi do |multi|
      multi.set("key", "other value")
      multi.incr("counter")
    end
  else
    redis.unwatch
  end
end
  # => ["OK", 6]

Without a block

redis.watch("key")
  # => "OK"

Parameters:

  • keys (String, Array<String>) —

    one or more keys to watch

Returns:

  • (Object) —

    if using a block, returns the return value of the block

  • (String) —

    if not using a block, returns ‘OK`

See Also:



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# File 'lib/redis/commands/transactions.rb', line 61

def watch(*keys)
  synchronize do |client|
    res = client.call_v([:watch] + keys)

    if block_given?
      begin
        yield(self)
      rescue ConnectionError
        raise
      rescue StandardError
        unwatch
        raise
      end
    else
      res
    end
  end
end