Ruby Method of the Day - Array.[] and Array.slice

Kelly McCauley — Mon, 29 Oct 2007 00:01:00 -0500

Signature

array[position]                 #=> object or nil
array.slice(position)           #=> object or nil

array[position] and array.slice(position) returns the object at position or returns nil if position is outside of array. If position is 0 or positive, then start counting from the beginning of the array. If position is negative, then start counting from the end of the array.

array[position, count]         #=> new_array or nil
array.slice(position, count)   #=> new_array or nil

array[position,count] and array.slice(position,count) returns new_array containing count number of objects starting from position. count must be a positive integer or nil is returned. If count is 0 then an empty array is returned (and not to mention executing useless method call). If position is positive and outside of array then an empty array is returned. If position is 0 or positive, then start counting from the beginning of the array. If position is negative, then start counting from the end of the array. If position is negative and outside of array then nil is returned.

array[range]                    #=> new_array or nil
array.slice(range)              #=> new_array or nil

array[range] and array.slice(range) returns new_array containing each object for all positions specified by range. If the start of the range is 0 or positive then start counting from the beginning of the array. If the start of the range is negative then start counting from the end of the array. If the start of the range is negative and outside of array then nil is returned.

Examples

a = [1, 2, "foo", 3, "bar", 4, -9]

a[0]          #=> 1
a[1]          #=> 2
a[-1]         #=> -9
a[20]         #=> nil
a[-20]        #=> nil

a[2,3]        #=> ["foo", 3, "bar"]
a[2,-3]       #=> nil
a[7,2]        #=> []
a[1,0]        #=> []
a[-2,3]       #=> [4, -9]
a[-3,3]       #=> ["bar", 4, -9]
a[-8,2]       #=> nil
a[99, 5]      #=> nil
a[-99, 5]     #=> nil

a[0..99]      #=> [1, 2, "foo", 3, "bar", 4, -9]
a[2..5]       #=> ["foo", 3, "bar", 4]
a[2..-4]      #=> ["foo", 3]
a[2..-99]     #=> []
a[7..10]      #=> []
a[0..0]       #=> [1]
a[-5..-2]     #=> ["foo", 3, "bar", 4]
a[-5..-1]     #=> ["foo", 3, "bar", 4, -9]
a[-5..-6]     #=> []
a[-99..-1]    #=> nil
a[-99..0]     #=> nil
a[-99..1]     #=> nil


a.slice(0)          #=> 1
a.slice(1)          #=> 2
a.slice(-1)         #=> -9
a.slice(20)         #=> nil
a.slice(-20)        #=> nil

a.slice(2,3)        #=> ["foo", 3, "bar"]
a.slice(2,-3)       #=> nil
a.slice(7,2)        #=> []
a.slice(1,0)        #=> []
a.slice(-2,3)       #=> [4, -9]
a.slice(-3,3)       #=> ["bar", 4, -9]
a.slice(-8,2)       #=> nil
a.slice(99, 5)      #=> nil
a.slice(-99, 5)     #=> nil


a.slice(0..99)      #=> [1, 2, "foo", 3, "bar", 4, -9]
a.slice(2..5)       #=> ["foo", 3, "bar", 4]
a.slice(2..-4)      #=> ["foo", 3]
a.slice(2..-99)     #=> []
a.slice(7..10)      #=> []
a.slice(0..0)       #=> [1]
a.slice(-5..-2)     #=> ["foo", 3, "bar", 4]
a.slice(-5..-1)     #=> ["foo", 3, "bar", 4, -9]
a.slice(-5..-6)     #=> []
a.slice(-99..-1)    #=> nil
a.slice(-99..0)     #=> nil
a.slice(-99..1)     #=> nil

Documentation Reference

Ruby version 1.8.6

Say what???: Ruby Method of the Day - Array.[] and Array.slice

Ruby Method of the Day - Array.[] and Array.slice

Signature

Examples

Documentation Reference