In Python, there is a built-in method called __getitem__, which you can add to your classes to make a custom implementation of getting an item. For example:
class containerlist (object):
def __init__(self, *args):
self.container = [x for x in args]
def __getitem__(self, i):
return self.container[i]
In Ruby, is there an equivalent for this or other Python built-ins like __len__ or __contains__?
In Ruby, you access items using [], the method is called, well, [].
Just to illustrate @Jörg W Mittag
class Containerlist
def initialize( *args)
@container = args
end
def [](i)
@container[i]
end
end
cl = Containerlist.new(3,4,5) #new creates a new obj and calls initialize
p cl[1] #interpreted as cl.[](1) # => 4
About __len__ : apparently, Python interprets len(a_list) as a_list.__len__, to accommodate beginning users. Ruby prefers size and/or length and does no such thing - it's just a_list.size . So:
class Containerlist
def size
@container.size
end
end
p cl.size # => 3
length of an array (also hashes) in ruby can written in (at least i know) two ways. calling length or count methods for an object. for string onjects you can use length method
irb(main):001:0> x = "some string"
=> "some string"
irb(main):002:0> x.class
=> String
irb(main):003:0> x.length
=> 11
irb(main):005:0> y = (1..9).to_a
=> [1, 2, 3, 4, 5, 6, 7, 8, 9]
irb(main):006:0> y.length
=> 9
irb(main):007:0> y.count
=> 9
irb(main):008:0>
__contains__ equivalent in ruby may be include? method. actually it's more likely to in keyword.
irb(main):008:0> x.include?('s')
=> true
irb(main):009:0> y.include?('2')
=> false
irb(main):010:0> y.include?(2)
=> true
find_index for arrays and index for string may be helpful.
irb(main):013:0> y.find_index(3)
=> 2
irb(main):016:0> x.index('s')
=> 0
irb(main):017:0> x.index('s', 4) #the second argument is offset value.
=> 5
I am not an experienced rubyist but hope these would be helpful for first steps. Also hope, not to mislead you on your ruby path :)
