Yield self if block_given?

ruby-talk
1

class AngstyNamedPerson
  attr_reader :name

  @@hated_names = %w(Leroy Sparkles Thaddius)

  def name=(new_name)
    @name = new_name
    raise "I have probems with being named #{@name}." if
@@hated_names.include? new_name
  end

  def initialize(name)
    @name = name
  end

  def transactionally(&block)
    old_name = @name
    begin
      yield self if block_given?
    rescue
      @name = old_name
    end
  end
end

mr_pibbles = AngstyNamedPerson.new('Mr. Pibbles')

···

--
In the code above, what's "yied self if block_given?" in the function
of transactionally?
I can't understand for the "self".

Please help with it.
Thanks.

2

I tried below, it can work,

irb(main):001:0> class Myclass
irb(main):002:1> def mya
irb(main):003:2> yield self if block_given?
irb(main):004:2> end
irb(main):005:1> def myb
irb(main):006:2> puts "it's myb"
irb(main):007:2> end
irb(main):008:1> end
=> nil
irb(main):009:0>
irb(main):010:0* x=Myclass.new
=> #<Myclass:0x83f81b0>
irb(main):012:0> x.mya { puts "a"}
a
=> nil
irb(main):013:0> x.mya { |c| c.myb }
it's myb
=> nil

···

------
in the code above, what's "c" there?
does it mean the instance of x itself?

Thanks again.

3

Hi,

class AngstyNamedPerson
  @@hated_names = %w(Leroy Sparkles Thaddius)

  attr_reader :name
  def name= new_name
    @name = new_name
    raise "I have probems with being named #{@name}." if @@hated_names.include? new_name
  end

  def initialize name
    @name = name
  end

  def transactionally
    old_name = @name
    begin
      yield self if block_given?
    rescue
      @name = old_name
    end
  end

end

mr_pibbles = AngstyNamedPerson.new 'Mr. Pibbles'

In the code above, what's "yied self if block_given?" in the function
of transactionally?
I can't understand for the "self".

I would like to tell it superfluous as in all regular cases the
caller yet has the object in a variable.

  p.transactionally { |p_|
    p.equal? p_ or raise "wrong library"
  }

It would rather make sense to check the new name before setting
the instance variable, instead of resetting it after the caller
changed it in some obscure place. Here's what I would have done:

  def check name
    some_condition or raise "I have probems with being named #{new_name}."
  end
  private :check

  def name= new_name
    check new_name
    @name = new_name
  end

  def transactionally tmp_name
    check tmp_name
    old_name, @name = @name, tmp_name
    begin
      yield
    ensure
      @name = old_name
    end
  end

Everything untested.

Bertram

···

Am Freitag, 01. Jan 2010, 23:54:12 +0900 schrieb Ruby Newbee:

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
*
Support `String#notempty?': <http://raa.ruby-lang.org/project/step&gt;\.

4

Hi

in the code above, what's "c" there?
does it mean the instance of x itself?

Yes it does.
Try
  x.mya {|c| p c}

···

---
Ayumu AIZAWA