You can always ditch extlib/hooks entirely and just overwrite save and
call super at some point
On Tue, Jan 12, 2010 at 17:14, Nick Howard <n...@baroquebobcat.com> wrote:
> On Fri, Jan 8, 2010 at 2:41 AM, Ben Lavender <blaven...@gmail.com> wrote:
>> I found myself today trying to do this, and failing:
>>
>> #!/usr/bin/env ruby
>> require 'rubygems'
>> require 'dm-core'
>>
>> DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/page.sqlite3")
>>
>> class Page
>> include DataMapper::Resource
>>
>> property :id, Serial # primary serial key
>> property :body, String # cannot be null
>> property :derived1, String
>>
>> after :save, :after_save
>>
>> def after_save
>> if attribute_get(:derived1).nil?
>> attribute_set(:derived1,body.to_s + ".db")
>> self.save
>> end
>> end
>> end
>> DataMapper.auto_migrate!
>> p = Page.new({ :body => "test123" })
>> p.save
>> p1 = Page.get(1)
>> puts p.inspect # derived1 => body + .db
>> puts p1.inspect # derived1 => nil
>>
>> Initially, I was trying to make a field be a default of (item.id).to_s
>> + "something", but this doesn't work with :default since attribute_get
>> isn't available to the class methods defining properties. So I came
>> up with something equivalent to this, and fought it for a while.
>>
>> I'm working around this now just fine--it was just a naive thing for
>> the first round of specs--but why does self.save not work in
>> after_save here? If it's failing on purpose (which I can imagine,
>> given the risk of infinite recursion with poor programming), wouldn't
>> it be better to raise an exception than to silently, magically fail?
>> Perhaps at least not return true?
>>
>> Thanks,
>> Ben
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "DataMapper" group.
>> To post to this group, send email to datamap...@googlegroups.com.
>> To unsubscribe from this group, send email to
>> datamapper+unsubscr...@googlegroups.com.
>> For more options, visit this group at
>> http://groups.google.com/group/datamapper?hl=en.
>>
>>
>>
>>
>
> Instead of `after :save` you could try using a lambda or Proc with
> default and doing something like
>
> property :derived1,String, :default => Proc.new { |r,l| "#{r.body}.db"}
>
> If you expect body to change after new is called, you could put it in
> a `before :save` call instead.
>
> before :save do
> self.derived1 = "#{r.body}.db"
> end
>
> or
>
>
> before :save do
> self.derived1 = "#{r.body}.db" unless derived1
> end
>
> if you don't want to clobber earlier values.
>
> --
> -Nick Howard
> http://blog.baroquebobcat.com/
>
> --
> You received this message because you are subscribed to the Google Groups
> "DataMapper" group.
> To post to this group, send email to datamap...@googlegroups.com.
> To unsubscribe from this group, send email to
> datamapper+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/datamapper?hl=en.
>
>
>
>
--
You received this message because you are subscribed to the Google Groups
"DataMapper" group.
To post to this group, send email to datamap...@googlegroups.com.
To unsubscribe from this group, send email to
datamapper+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/datamapper?hl=en.
