From: Tom Cloyd <tomcloyd@...>
Date: 2008-03-17T01:11:55+09:00
Subject: Re: argh! more undocumented mysteries: to_yaml

Stefano Crocco wrote:
> On Sunday 16 March 2008, Tom Cloyd wrote:
>   
>> Beginner woes, here, no doubt, but woes nevertheless.
>>
>> I'm exploring the wonders of the Object class, and I see Object#to_yaml.
>> Seems pretty obvious what to expect here, which would seem to account
>> for the total lack of documentation in each of the gazillion instances
>> of this method which appear in core library. Still, let's test it...
>>
>> irb(main):010:0> [2,5,3,6,'abc'].to_yaml
>> NoMethodError: undefined method `to_yaml' for [2, 5, 3, 6, "abc"]:Array
>>         from (irb):10
>>         from :0
>>
>> Can someone explain what just happened?
>>
>> Thanks!
>>
>> t.
>>     
>
> Yes. to_yaml is defined in the yaml.rb file, so you need to require it before 
> using to_yaml:
>
> irb(main):001:0> require 'yaml'
> => true
> irb(main):002:0> [2,3,4,5, 'abc'].to_yaml
> => "--- \n- 2\n- 3\n- 4\n- 5\n- abc\n"
>
> How are you supposed to know that to_yaml is not in ruby core but in the
> standard library? I don't really know. When I started using ruby some years
> ago, I downloaded a version of the rdoc documentation from
> www.ruby-doc.org which only included documentation for the core classes (that
> is, those you can use without need to require some files), while documentation 
> for the standard library was in a separate package. Unfortunately, the
> documentation you can find nowadays includes both core and standard library.
> This has the very unpleasant side effect of displaying together methods which 
> come from the core classes and methods which come from files in the standard
> library (which should be required before using such methods). At any rate, at 
> the top of the page, just below the name of the class, there's a list of the
> files which have been used to generate the documentation for the class. If a
> method listed in the documentation doesn't seem to exist, try requiring those 
> files. In the specific case of Object#to_yaml, this doesn't work, though,
> since the file where the method is defined, lib/yaml/rubytypes.rb, can't be
> required directly, but only requiring 'yaml'. It can give you a hint.
>
> Stefano
>
>
>   
Interesting. I have NO idea how I might have found this out, but I will 
make a note to try requiring something if it doesn't seem to be 
available. I fault myself for not thinking of that!

t.

-- 

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