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Ruby

Chen Wang
Chen Wang
7,371 Points
Posted by Chen Wang
Chen Wang
7,371 Points

Does ruby have a help method?

I'm new to ruby, and it seems like a really flexible language.

I have watched some ruby videos, and they just keeps invoking some method I have never seen.

I have java and python programming experiences. Therefore, I wonder if there is some helper method in ruby. Just like in python, you have

dir()    # show what method can be invoked 
help()  # show documents of a specific method.

Or in java , you can simply see those things in some IDE like Eclipse.

Thanks.

Anthony Lucio
Anthony Lucio
20,431 Points
Anthony Lucio
Anthony Lucio
20,431 Points

try ri within ruby.

here's a link if you need more info. (http://stackoverflow.com/questions/2009730/ruby-equivalent-to-pythons-help)

"It's definitely a poor cousin to ipython's help (and one of the main features I miss after moving to ruby), but you can also use ri from within irb. I'd recommend the wirble gem as an easy way to set this up."

2 Answers

John Steer-Fowler
PLUS
John Steer-Fowler
Courses Plus Student 11,734 Points
John Steer-Fowler
John Steer-Fowler
Courses Plus Student 11,734 Points

Yep, no problem. I see what you mean now.

You run the .methods method on the array to see which methods can be called.

Examples are better:

colors = ["Blue", "Green", "Red"]

colors.methods

=> [:inspect, :to_s, :to_a, :to_h, :to_ary, :frozen?, :==, :eql?, :hash, :[], :[]=, :at, :fetch, :first, :last, :concat, :<<, :push, :pop, :shift, :unshift, :insert, :each, :each_index, :reverse_each, :length, :size, :empty?, :find_index, :index, :rindex, :join, :reverse, :reverse!, :rotate, :rotate!, :sort, :sort!, :sort_by!, :collect, :collect!, :map, :map!, :select, :select!, :keep_if, :values_at, :delete, :delete_at, :delete_if, :reject, :reject!, :zip, :transpose, :replace, :clear, :fill, :include?, :<=>, :slice, :slice!, :assoc, :rassoc, :+, :*, :-, :&, :|, :uniq, :uniq!, :compact, :compact!, :flatten, :flatten!, :count, :shuffle!, :shuffle, :sample, :cycle, :permutation, :combination, :repeated_permutation, :repeated_combination, :product, :take, :take_while, :drop, :drop_while, :bsearch, :any?, :pack, :entries, :sort_by, :grep, :find, :detect, :find_all, :flat_map, :collect_concat, :inject, :reduce, :partition, :group_by, :all?, :one?, :none?, :min, :max, :minmax, :min_by, :max_by, :minmax_by, :member?, :each_with_index, :each_entry, :each_slice, :each_cons, :each_with_object, :chunk, :slice_before, :slice_after, :slice_when, :lazy, :nil?, :===, :=~, :!~, :class, :singleton_class, :clone, :dup, :itself, :taint, :tainted?, :untaint, :untrust, :untrusted?, :trust, :freeze, :methods, :singleton_methods, :protected_methods, :private_methods, :public_methods, :instance_variables, :instance_variable_get, :instance_variable_set, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :tap, :send, :public_send, :respond_to?, :extend, :display, :method, :public_method, :singleton_method, :define_singleton_method, :object_id, :to_enum, :enum_for, :equal?, :!, :!=, :instance_eval, :instance_exec, :__send__, :__id__]

Hope this helps

Chen Wang
Chen Wang
7,371 Points
Chen Wang
Chen Wang
7,371 Points

Yeah, this is exactly what I'm looking for.

Thanks John!!

John Steer-Fowler
John Steer-Fowler
Courses Plus Student 11,734 Points
John Steer-Fowler
John Steer-Fowler
Courses Plus Student 11,734 Points

You're welcome. I hope you get on well with Ruby, personally it's my favourite language.

Keep up the good work

John Steer-Fowler
PLUS
John Steer-Fowler
Courses Plus Student 11,734 Points
John Steer-Fowler
John Steer-Fowler
Courses Plus Student 11,734 Points

Hey Chen,

Yep, Ruby has this.

In your console, type 'ri' which will open Ruby Interative.

You can then enter methods such as .length or .max and it will give you some documentation on that method.

Use Ctrl + z to quit Ruby Interactive.

Hope this helps

Example

$ ri
$ .length
------------------------------------------------------------------------------
  length()

------------------------------------------------------------------------------

Returns the size of the collection calling size on the target. If the
collection has been already loaded, length and size are equivalent. If not and
you are going to need the records anyway this method will take one less query.
Otherwise size is more efficient.

  class Person < ActiveRecord::Base
    has_many :pets
  end

  person.pets.length # => 3
  # executes something like SELECT "pets".* FROM "pets" WHERE "pets"."person_id" = 1

  # Because the collection is loaded, you can
:
Chen Wang
Chen Wang
7,371 Points
Chen Wang
Chen Wang
7,371 Points

It helps, thank you John.

Besides that, is it possible for me to know what are the potential methods of a object?

For example, if I have an array, I want to add an new element to it. It's really hard to remember so many different method names. So in Java, if you type a dot after a array, it can show you what methods can be called. Similarly, python has dir() for that. Is there anything I can do with Ruby?