Dynamic programming advantage

Want to show you some pieces of Ruby code that do the same thing.

Original version:

FIELDS = [ 'first', 'last',      'band' ]
DATA   = [['Kurt',  'Cobain',    'Nirvana'],
        ['Jimi',  'Page',      'Led Zeppelin'],
        ['Noel',  'Gallagher', 'Oasis'],
        ['Thom',  'Yorke',     'Radiohead']]

def combine_fields_and_data(fields, data)
new_data = []
data.each do |row|
  row_hash = {}
  row.each_with_index do |column, i|
    row_hash[fields[i].to_sym] = column
  end
  new_data.push(row_hash)
end
return new_data
end

And Adam's refactoring

def combine_fields_and_data(fields, data)
data.map { |row| Hash[*fields.zip(row).flatten] }
end

Adam code utilize Ruby built-in Array and Hash utilities that make his code extremely short.

Read more about Array utilities here.

Ruby x.kind_of?

module M; end

class A; end

class B < A
  include M
end

b = B.new

b.kind_of? A # => true
b.kind_of? B # => true
b.kind_of? M # => true

b.class == A # => true
b.class == B # => false
b.class == M # => false

A === b # => true
B === b # => true
M === b # => true

Reference:
http://refactormycode.com/codes/487-x-kind_of-myclass-or-x-class-myclass

Ruby Paramater's Default Value

def foobar(a, b='b', c)
 ...
end

foobar(1, 2, 3)
 # a => 1
 # b => 2
 # c => 3

foobar(1, 2)
 # a => 1
 # b => 'b'
 # c => 2


define bar(a, b='b', c='c', d)

bar(1, 2, 3)
 # a => 1
 # b => 2
 # c => 'c'
 # d => 3

---
Prefer using default value for parameter from right to left direction

References:

• http://mwrc2008.confreaks.com/04katz.html

Ruby Equality

a = "a string"

a === "a string" # => true
a === String     # => false

String === "xyz"      # => true
"xyz".kind_of? String # => true

(1..5) === 3      # => true
(1..5).include? 3 # => true

/\d/ === "123" # => true

# === is used in "case" statement

b = a
a.equal? b # Returns true if the object_id’s are equal.

1 == 1.0   # => true (do type conversion)
1.==(1.0)  # underlying of ==
1.eql? 1.0 # => false (don't do type conversion)

References:

• http://probablycorey.wordpress.com/2008/02/26/ruby-equality-equal-eql-and/