From: Robert Klemme <shortcutter@...>
Date: 2009-10-09T05:40:12+09:00
Subject: Re: Mixing instance_eval and block with arguments

On 10/08/2009 06:52 PM, Jesús Gabriel y Galán wrote:
> On Thu, Oct 8, 2009 at 6:04 PM, Robert Klemme
> <shortcutter@googlemail.com> wrote:
>> Hi,
>>
>> here's what I'd like to do in a silly example:
>>
>> S = Struct.new :foo, :bar
>>
>> init = lambda do |a, b|
>>  self.foo = b
>>  self.bar = a + 10
>> end
>>
>> s = S.new # or create an instance otherwise
>>
>> # now comes the fun part which does not work
>> s.instance_eval(1, 2, &init)
>> => #<struct S foo=2, bar=11>
>>
>> In other words: I like to define a block as an initializer which I can
>> store away somewhere and invoke that initializer later on in the
>> context of "self" and pass arguments at the same time.  Any ideas how
>> I can accomplish this elegantly?
> 
> Probably not exactly what you want (can't make self to not be main
> inside the lambda), but what about:
> 
> irb(main):001:0> S = Struct.new :foo, :bar
> => S
> irb(main):003:0> s = S.new
> => #<struct S foo=nil, bar=nil>
> irb(main):040:0> def s.init(*args,&blk) #you can put this in a module
> and extend s with it, or add it to S
> irb(main):041:1> blk[self,*args]
> irb(main):042:1> end
> irb(main):043:0> init = lambda do |o,a,b|
> irb(main):044:1* o.foo = b
> irb(main):045:1> o.bar = a + 10
> irb(main):046:1> end
> => #<Proc:0xb7d78f18@(irb):43>
> irb(main):047:0> s.init(1,2,&init)
> => 11
> irb(main):048:0> s
> => #<struct S foo=2, bar=11>
> 
> Don't know if this is good enough.

Thank you!  Unfortunately I tried to avoid explicit passing of the 
reference.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/