How do I get the public methods of a class without inherited methods?

Question

Given any object I can call #public_methods and see all the methods it will respond to. However, I find it would sometimes be handy to get a quick list of all the public methods that are not inherited, i.e. the stuff that's really part of this class.

I found in "Easy way to list public methods for a Ruby object" that if I use:

(Foo.public_methods - Object.public_methods).sort

I can filter out a lot of basic Ruby stuff. I'd like to be able to filter everything that was inherited all the way up the chain. If I know the parent class I can filter using it, but I'd like to come up with a generic command that could return an array of the uninherited public methods for any object.

Solution 1

Just pass false for the inherited argument of public_methods:

"hello".public_methods.include?(:dup) # => true
"hello".public_methods(false).include?(:dup) # => false

Not an answer to your question, but in case you didn't know, irb does autocompletion, so it's easy to get the list of public methods (especially if you know the beginning of the method you are looking for). Just hit tab; hitting it twice will list all possibilities (including inherited ones, though):

> "nice".d<tab><tab>
"nice".delete      "nice".delete!    "nice".display   "nice".downcase                 
"nice".downcase!   "nice".dump       "nice".dup       "nice".define_singleton_method

> "nice".<tab><tab>
Display all 162 possibilities? (y or n)
...

Using pry makes it even easier to see the methods available, broken down by level of inheritance:

[1] pry(main)> cd "nice"
[2] pry("nice"):1> ls
Comparable#methods: <  <=  >  >=  between?
String#methods: %  *  +  <<  <=>  ==  ===  =~  []  []=  ascii_only?  bytes  bytesize  byteslice  capitalize  capitalize!  casecmp  center  chars  chomp  chomp!  chop  chop!  chr  clear  codepoints  concat  count  crypt  delete  delete!  downcase  downcase!  dump  each_byte  each_char  each_codepoint  each_line  empty?  encode  encode!  encoding  end_with?  eql?  force_encoding  getbyte  gsub  gsub!  hash  hex  include?  index  insert  inspect  intern  length  lines  ljust  lstrip  lstrip!  match  next  next!  oct  ord  partition  prepend  replace  reverse  reverse!  rindex  rjust  rpartition  rstrip  rstrip!  scan  setbyte  shellescape  shellsplit  size  slice  slice!  split  squeeze  squeeze!  start_with?  strip  strip!  sub  sub!  succ  succ!  sum  swapcase  swapcase!  to_c  to_f  to_i  to_r  to_s  to_str  to_sym  tr  tr!  tr_s  tr_s!  unpack  upcase  upcase!  upto  valid_encoding?
locals: _  _dir_  _ex_  _file_  _in_  _out_  _pry_

Solution 2

Take a look at Module#instance_methods. That method has one boolean argument include_super whether to return the inherited methods as well. Default value is true.

You can use the following:

class A 
  def method_1
     puts "method from A"
  end
end

class B < A
  def method_2
    puts "method from B"
  end
end

B.instance_methods        # => [:method_1, :method_2, ...]
B.instance_methods(false) # => [:method_2]

Comments

[Sergio Tulentsev]

did you mean irb or irc? :-)

[Marc-André Lafortune]

Indeed, irb. Thanks to you and @Mu

[Andrew]

Ah, super helpful! I didn't realize #public_methods accepted any arguments, and it didn't even occur to me to check. Thanks!

[Jochem Schulenklopper]

BTW, the comparable method on Object is called public_methods, see ruby-doc.org/core-2.5.1/Object.html#method-i-public_method. The method instance_methods is on the Module, see ruby-doc.org/core-2.5.1/Module.html#method-i-instance_method‌​s.