Ruby equivalent of Python's "dir"?

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In Python we can "dir" a module, like this:

>>> import re
>>> dir(re)

And it lists all functions in the module. Is there a similar way to do this in Ruby?

inspection ruby python
9 Answers

As far as I know not exactly but you get somewhere with

object.methods.sort
jonelf_446200

I like to have this in my .irbrc:

class Object
  def local_methods
    (methods - Object.instance_methods).sort
  end
end

So when I'm in irb:

>> Time.now.local_methods 
=> ["+", "-", "<", "<=", "<=>", ">", ">=", "_dump", "asctime", "between?", "ctime", "day", "dst?", "getgm", "getlocal", "getutc", "gmt?", "gmt_offset", "gmtime", "gmtoff", "hour", "isdst", "localtime", "mday", "min", "mon", "month", "sec", "strftime", "succ", "to_f", "to_i", "tv_sec", "tv_usec", "usec", "utc", "utc?", "utc_offset", "wday", "yday", "year", "zone"]

Or even cuter - with grep:

>> Time.now.local_methods.grep /str/
=> ["strftime"]
Commander_Keen_131940

Tip for "searching" for a method in irb: 

"something".methods.select {|item| item =~ /query/ }

Tip for trying out methods on a value for comparison:

value = "something"
[:upcase, :downcase, :capitalize].collect {|method| [method, value.send(method)] }

Also, note that you won't get all the same information as Python's dir with object.methods. You have to use a combination of object.methods and class.constants, also class.singleton_methods to get the class methods.

method_408830

The methods method will list all the methods that can be called on the object. It lists all the methods that the object's class defines.

>> "a string".methods
=> [:unicode_normalize, :unicode_normalize!, :ascii_only?, :to_r, :encode, ... ]

There are other methods like this, such as instance_methods which you can read about in the docs: e.g https://ruby-doc.org/core-2.7.3/Module.html#instance_methods-method

dylanfm_387950 
y String.methods.sort

gives a yaml representation of the sorted array of methods. Note that this can be used to list the methods of both classes and objects.

user_120370

Not really. Like the others said, you can get part of what you want by listing class instance methods (e.g. String.instance_methods) but that doesn't help you if a file you open reopens a class (unless you check before and after).

If you don't need programmatic access to the list of methods, consider checking out the documentation for a class, module or method using the ri command line tool.

user_98590

I would have made this a comment to jonelf's answer, but apparently I don't have enough rep.

some_object.methods.sort - Object.new.methods

This isn't exactly what you were asking as others have said, but it gives you the info you are after.

user_465050

If I stricly read your question, I must answer it that way: a file as specified by require in Ruby is just a container and does not have necessarely have any relation with a class. The content can be:

  • a class
  • a module
  • plain code

or any combination of the above, several times. So you can not directly ask for all methods in a given file.

If you meant to list all methods of a given module or class, then the other answers are what you seek (mainly using the #methods method on a module name or class).

Ollivier_Robert_161430
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