Iterate over a array and returning the next and the element before current [duplicate]
How may i fetch next and before current element from array while iterating array with each.
array.each do |a|
# I w开发者_开发技巧ant to fetch next and before current element.
end
Take look at Enumerable#each_cons
method:
[nil, *array, nil].each_cons(3){|prev, curr, nxt|
puts "prev: #{prev} curr: #{curr} next: #{nxt}"
}
prev: curr: a next: b
prev: a curr: b next: c
prev: b curr: c next:
If you like, you can wrap it in new Array method:
class Array
def each_with_prev_next &block
[nil, *self, nil].each_cons(3, &block)
end
end
#=> nil
array.each_with_prev_next do |prev, curr, nxt|
puts "prev: #{prev} curr: #{curr} next: #{nxt}"
end
You can use Enumerable#each_with_index
to get the index of each element as you iterate, and use that to get the surrounding items.
array.each_with_index do |a, i|
prev_element = array[i-1] unless i == 0
next_element = array[i+1] unless i == array.size - 1
end
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