Module: Transaction::Simple

Included in:
PDF::SimpleTable, PDF::Writer, ThreadSafe
Defined in:
lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb

Overview

Transaction::Simple for Ruby

Simple object transaction support for Ruby

Defined Under Namespace

Modules: ThreadSafe Classes: Group

Constant Summary collapse

TRANSACTION_SIMPLE_VERSION = 
'1.4.0'
SKIP_TRANSACTION_VARS = 
%w(@__transaction_checkpoint__ @__transaction_level__)

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.__common_start(name, vars, &block) ⇒ Object

Raises:



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 346

def __common_start(name, vars, &block)
  raise Transaction::TransactionError, Transaction::Messages[:cannot_start_empty_block_transaction] if vars.empty?

  if block
    begin
      vlevel = {}

      vars.each do |vv|
        vv.extend(Transaction::Simple)
        vv.start_transaction(name)
        vlevel[vv.__id__] = vv.instance_variable_get(:@__transaction_level__)
        vv.instance_variable_set(:@__transaction_block__, vlevel[vv.__id__])
      end

      yield(*vars)
    rescue Transaction::TransactionAborted
      vars.each do |vv|
        if name.nil? and vv.transaction_open?
          loop do
            tlevel = vv.instance_variable_get(:@__transaction_level__) || -1
            vv.instance_variable_set(:@__transaction_block__, -1)
            break if tlevel < vlevel[vv.__id__]
            vv.abort_transaction if vv.transaction_open?
          end
        elsif vv.transaction_open?(name)
          vv.instance_variable_set(:@__transaction_block__, -1)
          vv.abort_transaction(name)
        end
      end
    rescue Transaction::TransactionCommitted
      nil
    ensure
      vars.each do |vv|
        if name.nil? and vv.transaction_open?
          loop do
            tlevel = vv.instance_variable_get(:@__transaction_level__) || -1
            break if tlevel < vlevel[vv.__id__]
            vv.instance_variable_set(:@__transaction_block__, -1)
            vv.commit_transaction if vv.transaction_open?
          end
        elsif vv.transaction_open?(name)
          vv.instance_variable_set(:@__transaction_block__, -1)
          vv.commit_transaction(name)
        end
      end
    end
  else
    vars.each do |vv|
      vv.extend(Transaction::Simple)
      vv.start_transaction(name)
    end
  end
end

.debug_io ⇒ Object

Returns the Transaction::Simple debug object. It must respond to #<<.



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 75

def debug_io
  @tdi ||= ""
  @tdi
end

.debug_io=(io) ⇒ Object

Sets the Transaction::Simple debug object. It must respond to #<<. Debugging will be performed automatically if there’s a debug object.



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 58

def debug_io=(io)
  if io.nil?
    @tdi        = nil
    @debugging  = false
  else
    raise Transaction::TransactionError, Transaction::Messages[:bad_debug_object] unless io.respond_to?(:<<)
    @tdi = io
    @debugging = true
  end
end

.debugging? ⇒ Boolean

Returns true if we are debugging.

Returns:

  • (Boolean) 


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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 70

def debugging?
  defined? @debugging and @debugging
end

.start(*vars, &block) ⇒ Object

Start a named transaction in a block. The transaction will auto-commit when the block finishes.



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 409

def start(*vars, &block)
  __common_start(nil, vars, &block)
end

.start_named(name, *vars, &block) ⇒ Object

Start a named transaction in a block. The transaction will auto-commit when the block finishes.



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 403

def start_named(name, *vars, &block)
  __common_start(name, vars, &block)
end

Instance Method Details

#abort_transaction(name = nil) ⇒ Object

Aborts the transaction. Rewinds the object state to what it was before the transaction was started and closes the transaction. If name is specified, then the intervening transactions and the named transaction will be aborted. Otherwise, only the current transaction is aborted.

See #rewind_transaction for information about dealing with complex self-referential object graphs.

If the current or named transaction has been started by a block (Transaction::Simple.start), then the execution of the block will be halted with break self.

Raises:



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 232

def abort_transaction(name = nil)
  raise Transaction::TransactionError, Transaction::Messages[:cannot_abort_no_transaction] if @__transaction_checkpoint__.nil?

  # Check to see if we are trying to abort a transaction that is outside
  # of the current transaction block. Otherwise, raise TransactionAborted
  # if they are the same.
  defined? @__transaction_block__ or @__transaction_block__ = nil
  if @__transaction_block__ and name
    nix = @__transaction_names__.index(name) + 1
    raise Transaction::TransactionError, Transaction::Messages[:cannot_abort_transaction_before_block] if nix < @__transaction_block__

    raise Transaction::TransactionAborted if @__transaction_block__ == nix
  end

  raise Transaction::TransactionAborted if @__transaction_block__ == @__transaction_level__

  if name.nil?
    __abort_transaction(name)
  else
    raise Transaction::TransactionError, Transaction::Messages[:cannot_abort_named_transaction] % name.inspect unless @__transaction_names__.include?(name)
    __abort_transaction(name) while @__transaction_names__.include?(name)
  end

  self
end

#commit_transaction(name = nil) ⇒ Object

If name is nil (default), the current transaction level is closed out and the changes are committed.

If name is specified and name is in the list of named transactions, then all transactions are closed and committed until the named transaction is reached.

Raises:



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 264

def commit_transaction(name = nil)
  raise Transaction::TransactionError, Transaction::Messages[:cannot_commit_no_transaction] if @__transaction_checkpoint__.nil?
  @__transaction_block__ ||= nil

  # Check to see if we are trying to commit a transaction that is outside
  # of the current transaction block. Otherwise, raise
  # TransactionCommitted if they are the same.
  if @__transaction_block__ and name
    nix = @__transaction_names__.index(name) + 1
    raise Transaction::TransactionError, Transaction::Messages[:cannot_commit_transaction_before_block] if nix < @__transaction_block__

    raise Transaction::TransactionCommitted if @__transaction_block__ == nix
  end

  raise Transaction::TransactionCommitted if @__transaction_block__ == @__transaction_level__

  if name.nil?
    ss = "" if Transaction::Simple.debugging?
    __commit_transaction
    Transaction::Simple.debug_io << "#{'<' * @__transaction_level__} " << "Commit Transaction#{ss}\n" if Transaction::Simple.debugging?
  else
    raise Transaction::TransactionError, Transaction::Messages[:cannot_commit_named_transaction] % name.inspect unless @__transaction_names__.include?(name)
    ss = "(#{name})" if Transaction::Simple.debugging?

    while @__transaction_names__[-1] != name
      Transaction::Simple.debug_io << "#{'<' * @__transaction_level__} " << "Commit Transaction#{ss}\n" if Transaction::Simple.debugging?
      __commit_transaction
    end
    Transaction::Simple.debug_io << "#{'<' * @__transaction_level__} " << "Commit Transaction#{ss}\n" if Transaction::Simple.debugging?
    __commit_transaction
  end

  self
end

#rewind_transaction(name = nil) ⇒ Object

Rewinds the transaction. If name is specified, then the intervening transactions will be aborted and the named transaction will be rewound. Otherwise, only the current transaction is rewound.

After each level of transaction is rewound, if the callback method #_post_transaction_rewind is defined, it will be called. It is intended to allow a complex self-referential graph to fix itself. The simplest way to explain this is with an example.

class Child
  attr_accessor :parent
end

class Parent
  include Transaction::Simple

  attr_reader :children
  def initialize
    @children = []
  end

  def << child
    child.parent = self
    @children << child
  end

  def valid?
    @children.all? { |child| child.parent == self }
  end
end

parent = Parent.new
parent << Child.new
parent.start_transaction
parent << Child.new
parent.abort_transaction
puts parent.valid? # => false

This problem can be fixed by modifying the Parent class to include the #_post_transaction_rewind callback.

class Parent
  # Reconnect the restored children to me, instead of to the bogus me
  # that was restored to them by Marshal::load.
  def _post_transaction_rewind
    @children.each { |child| child.parent = self }
  end
end

parent = Parent.new
parent << Child.new
parent.start_transaction
parent << Child.new
parent.abort_transaction
puts parent.valid? # => true

Raises:



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 187

def rewind_transaction(name = nil)
  raise Transaction::TransactionError, Transaction::Messages[:cannot_rewind_no_transaction] if @__transaction_checkpoint__.nil?

  # Check to see if we are trying to rewind a transaction that is
  # outside of the current transaction block.
  defined? @__transaction_block__ or @__transaction_block__ = nil
  if @__transaction_block__ and name
    nix = @__transaction_names__.index(name) + 1
    raise Transaction::TransactionError, Transaction::Messages[:cannot_rewind_transaction_before_block] if nix < @__transaction_block__
  end

  if name.nil?
    checkpoint = @__transaction_checkpoint__
    __rewind_this_transaction
    @__transaction_checkpoint__ = checkpoint
    ss = "" if Transaction::Simple.debugging?
  else
    raise Transaction::TransactionError, Transaction::Messages[:cannot_rewind_named_transaction] % name.inspect unless @__transaction_names__.include?(name)
    ss = "(#{name})" if Transaction::Simple.debugging?

    while @__transaction_names__[-1] != name
      @__transaction_checkpoint__ = __rewind_this_transaction
      Transaction::Simple.debug_io << "#{'|' * @__transaction_level__} " << "Rewind Transaction#{ss}\n" if Transaction::Simple.debugging?
      @__transaction_level__ -= 1
      @__transaction_names__.pop
    end
    checkpoint = @__transaction_checkpoint__
    __rewind_this_transaction
    @__transaction_checkpoint__ = checkpoint
  end
  Transaction::Simple.debug_io << "#{'|' * @__transaction_level__} " << "Rewind Transaction#{ss}\n" if Transaction::Simple.debugging?
  self
end

#start_transaction(name = nil) ⇒ Object

Starts a transaction. Stores the current object state. If a transaction name is specified, the transaction will be named. Transaction names must be unique. Transaction names of nil will be treated as unnamed transactions.

Raises:



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 111

def start_transaction(name = nil)
  @__transaction_level__ ||= 0
  @__transaction_names__ ||= []

  name = name.dup.freeze if name.kind_of?(String)

  raise Transaction::TransactionError, Transaction::Messages[:unique_names] if name and @__transaction_names__.include?(name)

  @__transaction_names__ << name
  @__transaction_level__ += 1

  if Transaction::Simple.debugging?
    ss = "(#{name.inspect})"
    ss = "" unless ss

    Transaction::Simple.debug_io << "#{'>' * @__transaction_level__} " << "Start Transaction#{ss}\n"
  end

  @__transaction_checkpoint__ = Marshal.dump(self)
end

#transaction(action = nil, name = nil) ⇒ Object

Alternative method for calling the transaction methods. An optional name can be specified for named transaction support. This method is deprecated and will be removed in Transaction::Simple 2.0.

#transaction(:start)

#start_transaction

#transaction(:rewind)

#rewind_transaction

#transaction(:abort)

#abort_transaction

#transaction(:commit)

#commit_transaction

#transaction(:name)

#transaction_name

#transaction

#transaction_open?



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 309

def transaction(action = nil, name = nil)
  _method = case action
            when :start then :start_transaction
            when :rewind then :rewind_transaction
            when :abort then :abort_transaction
            when :commit then :commit_transaction
            when :name then :transaction_name
            when nil then :transaction_open?
            else nil
            end

  if method
    warn "The #transaction method has been deprecated. Use #{method} instead."
  else
    warn "The #transaction method has been deprecated."
  end

  case method
  when :transaction_name
    __send__ method
  when nil
    nil
  else
    __send__ method, name
  end
end

#transaction_exclusions ⇒ Object

Allows specific variables to be excluded from transaction support. Must be done after extending the object but before starting the first transaction on the object.

vv.transaction_exclusions << "@io"



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 341

def transaction_exclusions
  @transaction_exclusions ||= []
end

#transaction_name ⇒ Object

Returns the current name of the transaction. Transactions not explicitly named are named nil.

Raises:



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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 97

def transaction_name
  raise Transaction::TransactionError, Transaction::Messages[:no_transaction_open] if @__transaction_checkpoint__.nil?
  Transaction::Simple.debug_io << "#{'|' * @__transaction_level__} " << "Transaction Name: #{@__transaction_names__[-1].inspect}\n" if Transaction::Simple.debugging?
  if @__transaction_names__[-1].kind_of?(String)
    @__transaction_names__[-1].dup
  else
    @__transaction_names__[-1]
  end
end

#transaction_open?(name = nil) ⇒ Boolean

If name is nil (default), then returns true if there is currently a transaction open. If name is specified, then returns true if there is currently a transaction known as name open.

Returns:

  • (Boolean) 


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# File 'lib/gems/transaction-simple-1.4.0/lib/transaction/simple.rb', line 84

def transaction_open?(name = nil)
  defined? @__transaction_checkpoint__ or @__transaction_checkpoint__ = nil
  if name.nil?
    Transaction::Simple.debug_io << "Transaction " << "[#{(@__transaction_checkpoint__.nil?) ? 'closed' : 'open'}]\n" if Transaction::Simple.debugging?
    return (not @__transaction_checkpoint__.nil?)
  else
    Transaction::Simple.debug_io << "Transaction(#{name.inspect}) " << "[#{(@__transaction_checkpoint__.nil?) ? 'closed' : 'open'}]\n" if Transaction::Simple.debugging?
    return ((not @__transaction_checkpoint__.nil?) and @__transaction_names__.include?(name))
  end
end