I need to create some objects of different (custom) classes, in
different pages of my site, so I made some code that takes an array of
hashes and create the objects. the hashes are like this one:
h = { :class => Class1, :param1 => 'foo', :param2 => 'bar', etc }
and basically I do
object = h[:class].new(h)
everything works fine as long as the hash is defined inside the source
code. however in some case I need to create the same object in two
different file. to avoid writing the same hashes twice I though about
putting them in a YAML file but this method doesn't work anymore because
the class name is converted to a string instead of a reference to the
class, using !ruby/object creates the object but all the code inside the
initialize method seems to be never executed (or the instance variables
ovverrided after the inzialize method) so my objects don't work,
ClassName.to_yaml returns an error, etc...
is there a way to do what I want to do? putting the ashes in a file and
loading them as a source AFAIK creates other problem due to the
sandboxing made by mod_ruby, that's why I tried with yaml.
···
--
Deh! Impiacciami, imploroti
sgabazzone rampante!
Tirsdag den 13. Marts 2007 skrev Matteo Cavalleri:
I need to create some objects of different (custom) classes, in
different pages of my site, so I made some code that takes an array of
hashes and create the objects. the hashes are like this one:
h = { :class => Class1, :param1 => 'foo', :param2 => 'bar', etc }
and basically I do
object = h[:class].new(h)
everything works fine as long as the hash is defined inside the source
code. however in some case I need to create the same object in two
different file. to avoid writing the same hashes twice I though about
putting them in a YAML file but this method doesn't work anymore because
the class name is converted to a string instead of a reference to the
class, using !ruby/object creates the object but all the code inside the
initialize method seems to be never executed (or the instance variables
ovverrided after the inzialize method) so my objects don't work,
ClassName.to_yaml returns an error, etc...
is there a way to do what I want to do? putting the ashes in a file and
loading them as a source AFAIK creates other problem due to the
sandboxing made by mod_ruby, that's why I tried with yaml.
Object.const_get can convert a String to a constant, so if you do:
Object.const_get(h[:class].to_s).new(h)
it should work, no matter if the hash comes from source or yaml
br. Chr.
It seems to me this is a fundamental problem with YAML. Even if you were trying to put all the data in one file, I don't believe the YAML spec. addresses writing object references instead of objects. This is especially an issue when your objects have circular references.
This caused me to use XML instead of YAML for a recent Java project because the Java XStream library handles serializing and deserializing Java objects that have circular references.
If there is a YAML solution to this, I'd love to hear about it!
···
On Mar 13, 2007, at 9:50 AM, Matteo Cavalleri wrote:
I need to create some objects of different (custom) classes, in
different pages of my site, so I made some code that takes an array of
hashes and create the objects. the hashes are like this one:
h = { :class => Class1, :param1 => 'foo', :param2 => 'bar', etc }
and basically I do
object = h[:class].new(h)
everything works fine as long as the hash is defined inside the source
code. however in some case I need to create the same object in two
different file. to avoid writing the same hashes twice I though about
putting them in a YAML file but this method doesn't work anymore because
the class name is converted to a string instead of a reference to the
class, using !ruby/object creates the object but all the code inside the
initialize method seems to be never executed (or the instance variables
ovverrided after the inzialize method) so my objects don't work,
ClassName.to_yaml returns an error, etc...
is there a way to do what I want to do? putting the ashes in a file and
loading them as a source AFAIK creates other problem due to the
sandboxing made by mod_ruby, that's why I tried with yaml.
If you reference the class object directly, you can't dump it to yaml, so
try using a string instead, and running eval on the string to get the
class object.
h = { :class => 'Class1', :param1 => 'foo', :param2 => 'bar', etc }
object = eval(h[:class]).new(h)
This gives you the following YAML:
···
On Tue, 13 Mar 2007 15:47:13 +0100, Matteo Cavalleri wrote:
I need to create some objects of different (custom) classes, in
different pages of my site, so I made some code that takes an array of
hashes and create the objects. the hashes are like this one:
h = { :class => Class1, :param1 => 'foo', :param2 => 'bar', etc }
and basically I do
object = h[:class].new(h)
everything works fine as long as the hash is defined inside the source
code. however in some case I need to create the same object in two
different file. to avoid writing the same hashes twice I though about
putting them in a YAML file but this method doesn't work anymore because
the class name is converted to a string instead of a reference to the
class, using !ruby/object creates the object but all the code inside the
initialize method seems to be never executed (or the instance variables
ovverrided after the inzialize method) so my objects don't work,
ClassName.to_yaml returns an error, etc...
is there a way to do what I want to do? putting the ashes in a file and
loading them as a source AFAIK creates other problem due to the
sandboxing made by mod_ruby, that's why I tried with yaml.
---
:class: Class1
:param1: foo
:param2: bar
--
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/
Matteo Cavalleri wrote:
I need to create some objects of different (custom) classes, in
different pages of my site, so I made some code that takes an array of
hashes and create the objects. the hashes are like this one:
h = { :class => Class1, :param1 => 'foo', :param2 => 'bar', etc }
and basically I do
object = h[:class].new(h)
everything works fine as long as the hash is defined inside the source
code. however in some case I need to create the same object in two
different file. to avoid writing the same hashes twice I though about
putting them in a YAML file but this method doesn't work anymore because
the class name is converted to a string instead of a reference to the
class, using !ruby/object creates the object but all the code inside the
initialize method seems to be never executed (or the instance variables
ovverrided after the inzialize method) so my objects don't work,
ClassName.to_yaml returns an error, etc...
is there a way to do what I want to do? putting the ashes in a file and
loading them as a source AFAIK creates other problem due to the
sandboxing made by mod_ruby, that's why I tried with yaml.
It is possible to extend YAML to serialize classes:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/177604
It seems to still work with ruby-1.8.6.
It lets you do this:
yy = [Enumerable, Comparable, String, File].to_yaml
puts yy
p YAML.load(yy)
with output:
···
---
- !ruby/module Enumerable
- !ruby/module Comparable
- !ruby/class String
- !ruby/class File
[Enumerable, Comparable, String, File]
However, if you are hand-editing the YAML file, you may find that a class name string is more convenient than this notation.
YYAMLMMV
--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
harp:~ > ruby -r yaml -e' h = {}; h[:h] = h; y h '
&id001
:h: *id001
regards.
-a
···
On Wed, 14 Mar 2007, Mark Volkmann wrote:
It seems to me this is a fundamental problem with YAML. Even if you were trying to put all the data in one file, I don't believe the YAML spec. addresses writing object references instead of objects. This is especially an issue when your objects have circular references.
This caused me to use XML instead of YAML for a recent Java project because the Java XStream library handles serializing and deserializing Java objects that have circular references.
If there is a YAML solution to this, I'd love to hear about it!
--
be kind whenever possible... it is always possible.
- the dalai lama
the idea was excellent but it seems it doens't work if the class I need
is defined in another class namespace, e.g.
irb(main):117:0> Object.const_get('CGI::Cookie')
NameError: wrong constant name CGI::Cookie
anyway thanks for the help
···
Christian Surlykke <christian@surlykke.dk> wrote:
Object.const_get can convert a String to a constant, so if you do:
Object.const_get(h[:class].to_s).new(h)
it should work, no matter if the hash comes from source or yaml
--
Deh! Impiacciami, imploroti
sgabazzone rampante!
mh... if I don't find a solution with yaml I'll try xml with ruby.
thanks.
···
Mark Volkmann <mark@ociweb.com> wrote:
This caused me to use XML instead of YAML for a recent Java project
--
Deh! Impiacciami, imploroti
sgabazzone rampante!
I think i'll go for the class name string 
but thanks for the link to
the extension. as I'm still learning ruby it was very interesting.
···
Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
However, if you are hand-editing the YAML file, you may find that a
class name string is more convenient than this notation.
--
Deh! Impiacciami, imploroti
sgabazzone rampante!
My apologies! Apparently the problem is with the Java implementation of YAML that I was using and not with YAML itself. Here's a more full example that demonstrates YAML doing the right thing with multiple references to the same object and with circular references.
···
On Mar 13, 2007, at 10:28 AM, ara.t.howard@noaa.gov wrote:
On Wed, 14 Mar 2007, Mark Volkmann wrote:
It seems to me this is a fundamental problem with YAML. Even if you were trying to put all the data in one file, I don't believe the YAML spec. addresses writing object references instead of objects. This is especially an issue when your objects have circular references.
This caused me to use XML instead of YAML for a recent Java project because the Java XStream library handles serializing and deserializing Java objects that have circular references.
If there is a YAML solution to this, I'd love to hear about it!
harp:~ > ruby -r yaml -e' h = {}; h[:h] = h; y h '
&id001
:h: *id001
---
require 'yaml'
class Person
attr_accessor :name, :spouse, :address
def to_s
"\n#{name} is married to #{spouse.name} and lives at\n#{address}"
end
end
class Address
attr_accessor :street, :city, :state, :zip
def to_s
"#{street}\n#{city}, #{state} #{zip}"
end
end
a = Address.new
a.street = "644 Glen Summit"
a.city = "St. Charles"
a.state = "MO"
a.zip = 63304
p1 = Person.new
p1.name = "Mark Volkmann"
p1.address = a
p2 = Person.new
p2.name = "Tami Volkmann"
p2.address = a
p1.spouse = p2
p2.spouse = p1
people = [p1, p2]
yaml_string = YAML::dump(people)
puts yaml_string
new_people = YAML::load(yaml_string)
puts new_people
---
The output is
---
- &id002 !ruby/object:Person
address: &id001 !ruby/object:Address
city: St. Charles
state: MO
street: 644 Glen Summit
zip: 63304
name: Mark Volkmann
spouse: &id003 !ruby/object:Person
address: *id001
name: Tami Volkmann
spouse: *id002
- *id003
Mark Volkmann is married to Tami Volkmann and lives at
644 Glen Summit
St. Charles, MO 63304
Tami Volkmann is married to Mark Volkmann and lives at
644 Glen Summit
St. Charles, MO 63304
Alle martedì 13 marzo 2007, Matteo Cavalleri ha scritto:
> Object.const_get can convert a String to a constant, so if you do:
>
> Object.const_get(h[:class].to_s).new(h)
>
> it should work, no matter if the hash comes from source or yaml
the idea was excellent but it seems it doens't work if the class I need
is defined in another class namespace, e.g.
irb(main):117:0> Object.const_get('CGI::Cookie')
NameError: wrong constant name CGI::Cookie
anyway thanks for the help
Can't you store the class name (using Class#name) instead of the class itself
in the yaml file? This way, since Class#name returns the full 'path',
including modules, you can then do something like:
name=h[:class]
name.split('::').inject(Object){|res, c| c.const_get(c)}.new h
(taken from the solutions of the ruby quiz 133
(http://www.rubyquiz.com/quiz113.html\))
I hope this helps
Stefano
···
Christian Surlykke <christian@surlykke.dk> wrote:
this is pretty complicated for my current knowledge of ruby 
the
method suggested by ken bloom works and is simpler for me, but thanks
anyway for you help!
···
Stefano Crocco <stefano.crocco@alice.it> wrote:
name.split('::').inject(Object){|res, c| c.const_get(c)}.new h
--
Deh! Impiacciami, imploroti
sgabazzone rampante!
To get at Foo::Bar::Baz you need to do
klass = Object.const_get("Foo").const_get("Bar").const_get("Baz")
So that one-liner above is really another way of writing:
name = "Foo::Bar::Baz"
names = name.split("::")
klass = Object
while n = names.shift
klass = klass.const_get(n)
end
···
On Wed, Mar 14, 2007 at 01:25:06AM +0900, Matteo Cavalleri wrote:
Stefano Crocco <stefano.crocco@alice.it> wrote:
> name.split('::').inject(Object){|res, c| c.const_get(c)}.new h
this is pretty complicated for my current knowledge of ruby the
method suggested by ken bloom works and is simpler for me, but thanks
anyway for you help!