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# frozen_string_literal: true
class Redis
module Commands
module Transactions
# Mark the start of a transaction block.
#
# @example With a block
# redis.multi do |multi|
# multi.set("key", "value")
# multi.incr("counter")
# end # => ["OK", 6]
#
# @yield [multi] the commands that are called inside this block are cached
# and written to the server upon returning from it
# @yieldparam [Redis] multi `self`
#
# @return [Array<...>]
# - an array with replies
#
# @see #watch
# @see #unwatch
def multi
synchronize do |client|
client.multi do |raw_transaction|
yield MultiConnection.new(raw_transaction)
end
end
end
# 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.
#
# @example 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]
#
# @example Without a block
# redis.watch("key")
# # => "OK"
#
# @param [String, Array<String>] keys one or more keys to watch
# @return [Object] if using a block, returns the return value of the block
# @return [String] if not using a block, returns `OK`
#
# @see #unwatch
# @see #multi
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
# Forget about all watched keys.
#
# @return [String] `OK`
#
# @see #watch
# @see #multi
def unwatch
send_command([:unwatch])
end
# Execute all commands issued after MULTI.
#
# Only call this method when `#multi` was called **without** a block.
#
# @return [nil, Array<...>]
# - when commands were not executed, `nil`
# - when commands were executed, an array with their replies
#
# @see #multi
# @see #discard
def exec
send_command([:exec])
end
# Discard all commands issued after MULTI.
#
# @return [String] `"OK"`
#
# @see #multi
# @see #exec
def discard
send_command([:discard])
end
end
end
end
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