to_yaml method for array

[Raj Singh]

This is irb.

irb

irb(main):001:0> a = %w[ 1 2 3 ]
=> ["1", "2", "3"]
irb(main):002:0> a.to_yaml
NoMethodError: undefined method `to_yaml' for ["1", "2", "3"]:Array
from (irb):2


This is Rails script/console

a = %w[ 1 2 3] => ["1", "2", "3"]
a.to_yaml

=> "--- \n- \"1\"\n- \"2\"\n- \"3\"\n"


However no where in ActiveSupport I can find where Rails is implementing
the method to_yaml.

I go to http://www.ruby-doc.org/core/ and look for Array methods. I see
to_yaml. So why in the irb I am getting undefined method to_yaml?

 

[Jason Roelofs]

require 'yaml'

This is irb.

irb

irb(main):001:0> a = %w[ 1 2 3 ]
=> ["1", "2", "3"]
irb(main):002:0> a.to_yaml
NoMethodError: undefined method `to_yaml' for ["1", "2", "3"]:Array
from (irb):2


This is Rails script/console

a = %w[ 1 2 3] => ["1", "2", "3"]
a.to_yaml

=> "--- \n- \"1\"\n- \"2\"\n- \"3\"\n"


However no where in ActiveSupport I can find where Rails is implementing
the method to_yaml.

I go to http://www.ruby-doc.org/core/ and look for Array methods. I see
to_yaml. So why in the irb I am getting undefined method to_yaml?

 

[Phillip Gawlowski]

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Raj Singh wrote:

| However no where in ActiveSupport I can find where Rails is implementing
| the method to_yaml.
|
| I go to http://www.ruby-doc.org/core/ and look for Array methods. I see
| to_yaml. So why in the irb I am getting undefined method to_yaml?

require 'yaml'

This adds the desired functionality. Alas, the RDoc generated
(currently) includes functions in Core lib that are *actually* part of
STDLIB.

- --
Phillip Gawlowski
Twitter: twitter.com/cynicalryan
Blog: http://justarubyist.blogspot.com

A born loser:
~ Somebody who calls the number that's scrawled in lipstick on the phone
~ booth wall-- and his wife answers.
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[Sean O'Halpin]

I go to http://www.ruby-doc.org/core/ and look for Array methods. I see
to_yaml. So why in the irb I am getting undefined method to_yaml?

You need to

require 'yaml'

to load the yaml library.

Regards,
Sean

 

[Stefano Crocco]

This is irb.

irb

irb(main):001:0> a = %w[ 1 2 3 ]
=> ["1", "2", "3"]
irb(main):002:0> a.to_yaml
NoMethodError: undefined method `to_yaml' for ["1", "2", "3"]:Array
from (irb):2


This is Rails script/console

a = %w[ 1 2 3]

=> ["1", "2", "3"]

=> "--- \n- \"1\"\n- \"2\"\n- \"3\"\n"


However no where in ActiveSupport I can find where Rails is implementing
the method to_yaml.

I go to http://www.ruby-doc.org/core/ and look for Array methods. I see
to_yaml. So why in the irb I am getting undefined method to_yaml?

You need to require 'yaml' before using the Array#to_yaml method (or any other
predefined to_yaml methods, for the matter). I guess Rails console already
does that itself, so there your code works. Regarding the documentation,
unfortunately the one you mention mixes 'core' classes (that is, classes and
modules which are always availlable) and 'standard library' classes (classes
and modules which are distributed with ruby but need to be required to be
used). The to_yaml method is defined in a file in the standard library, but
that can't be guessed from the documentation. If you want to generate the
documentation for only the core classes, you can follow the procedure
explained in this thread:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/294786
The documentation for only the standard library can be downloaded here:
http://www.ruby-doc.org/stdlib/

I hope this helps

Stefano

 

[James Britt]

I go to http://www.ruby-doc.org/core/ and look for Array methods. I see
to_yaml. So why in the irb I am getting undefined method to_yaml?

rdoc, run over the ruby source, is dopey in that it parses the yaml
files, sees that they modify core Ruby objects, then generates rdoc that
presents those core objects as if they had yaml methods built-in.

In actual practice, you have to explicitly mix-in yaml to get that behavior.

 

[Stefano Crocco]

rdoc, run over the ruby source, is dopey in that it parses the yaml
files, sees that they modify core Ruby objects, then generates rdoc that
presents those core objects as if they had yaml methods built-in.

In actual practice, you have to explicitly mix-in yaml to get that
behavior.

Actually, you don't need to mix-in yaml. When you require yaml.rb, it will add
the generic to_yaml method to the Object class itself (or to the Kernel
module, I'm not sure) and the more specialized methods to those classes for
which they exist (such as Array, String and Hash). There's no mixing-in
involved, as far as I can tell.

Stefano

 

[Marc Heiler]

You followup-guys are overkilling on such a simple question with such a
simple solution... i am sure in some time there be dragons! ;-)

 

[Phillip Gawlowski]

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Marc Heiler wrote:
| You followup-guys are overkilling on such a simple question with such a
| simple solution... i am sure in some time there be dragons! ;-)

Though, if somebody uses a search engine, the chance of finding a
solution to the same problem by somebody else increases.

Also, explanations as to *why* something is not the way as it is
expected helps in troubleshooting problems of a similar nature.

- --
Phillip Gawlowski
Twitter: twitter.com/cynicalryan
Blog: http://justarubyist.blogspot.com

ZEAL:
Quality seen in new graduates -- if you're quick.
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[James Britt]

Actually, you don't need to mix-in yaml. When you require yaml.rb, it will add
the generic to_yaml method to the Object class itself (or to the Kernel
module, I'm not sure) and the more specialized methods to those classes for
which they exist (such as Array, String and Hash). There's no mixing-in
involved, as far as I can tell.

Yes, you are quite right.