Confusion with the UnboundMethod#source_location method

ruby-talk
1

I read the UnboundMethod#source_location
(http://www.ruby-doc.org/core-2.0/UnboundMethod.html#method-i-source_location)
says:

(a) Returns the Ruby source filename and line number containing this
method (b) `nil` if this method was not defined in Ruby (i.e. native)

class Foo
    def snow
        "wow"
    end
end

Foo.instance_method(:snow) # => #<UnboundMethod: Foo#snow>
Foo.instance_method(:snow).source_location
# => ["-", 2]

--in the above case - why does the "source file name" not come ?

String.instance_method(:to_str) # => #<UnboundMethod: String#to_str>
String.instance_method(:to_str).source_location
# => nil

--in the above case - why does the `nil` come ?

···

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2

you run the file directly in ruby right? "-" means it was defined in
ruby interpreter itself and not in a file.

irb would show "(irb)"

String.instance_method(:to_str) # => #<UnboundMethod: String#to_str>
String.instance_method(:to_str).source_location
# => nil

--in the above case - why does the `nil` come ?

like you already said: "nil" means native, so to_str is defined in C for
the MRI interpreter

···

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3

for an external binding or functions that are defined inside C or C++
code,
once compiled ruby cant get the location anymore (because the compiled
lib files are not parse-able)

its also the same for the parameters

···

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Posted via http://www.ruby-forum.com/.

4

Hans Mackowiak wrote in post #1119477:

you run the file directly in ruby right? "-" means it was defined in
ruby interpreter itself and not in a file.

irb would show "(irb)"

Thank you very much "Mr. Expert".. I understood now.

Here is my try:-

···

================

kirti@kirti-Aspire-5733Z:~$ irb
2.0.0p0 :001 > class Foo
2.0.0p0 :002?> def wow
2.0.0p0 :003?> 1
2.0.0p0 :004?> end
2.0.0p0 :005?> end
=> nil
2.0.0p0 :006 > Foo.instance_method(:wow).source_location
=> ["(irb)", 2]
2.0.0p0 :007 > require "./SO.rb"
LoadError: cannot load such file -- ./SO.rb
  from
/home/kirti/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in
`require'
  from
/home/kirti/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in
`require'
  from (irb):7
  from /home/kirti/.rvm/rubies/ruby-2.0.0-p0/bin/irb:16:in `<main>'
2.0.0p0 :008 > require 'fileutils'
=> true
2.0.0p0 :009 > FileUtils.pwd
=> "/home/kirti"
2.0.0p0 :010 > FileUtils.cd '/home/kirti/ruby'
=> nil
2.0.0p0 :011 > require "./SO.rb"
=> true
2.0.0p0 :012 > Foo.instance_method(:snow).source_location
=> ["/home/kirti/ruby/SO.rb", 2]
2.0.0p0 :013 >

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5

Hey Hans,

Can you explain your comment that nil means native? Nil usually is returned
when it can't find the source location so nil is returned since ruby always
returns *something*.

Not saying you're wrong, just trying to understand how you came to that
conclusion as it differs from what I know of Ruby.

Thanks

···

On Aug 23, 2013 6:36 PM, "Hans Mackowiak" <lists@ruby-forum.com> wrote:

you run the file directly in ruby right? "-" means it was defined in
ruby interpreter itself and not in a file.

irb would show "(irb)"

String.instance_method(:to_str) # => #<UnboundMethod: String#to_str>
String.instance_method(:to_str).source_location
# => nil

--in the above case - why does the `nil` come ?

like you already said: "nil" means native, so to_str is defined in C for
the MRI interpreter

--
Posted via http://www.ruby-forum.com/\.

6

Thanks for clarifying for me.

···

On Aug 24, 2013 3:26 PM, "Hans Mackowiak" <lists@ruby-forum.com> wrote:

for an external binding or functions that are defined inside C or C++
code,
once compiled ruby cant get the location anymore (because the compiled
lib files are not parse-able)

its also the same for the parameters

--
Posted via http://www.ruby-forum.com/\.