Lets say I have an array like so:
['x','cat', 'dog', 'x', 'dolphin', 'cougar', 'whale']
I don't know the length of the array or when an 'x' will occur. When I reach 'x' I want to push the following elements into a new array until I reach the next element that includes?('x').
The desired output would be:
[['cat', 'dog']['dolphin','cougar', 'whale']]
How can I achieve this?
Enumerable#slice_before makes this simple:
a = ['x','cat', 'dog', 'x', 'dolphin', 'cougar', 'whale']
a.slice_before(/\Ax\z/).map { |chunk| chunk.drop(1) }
=> [["cat", "dog"], ["dolphin", "cougar", "whale"]]
slice_before. It's made for exactly this situation.ar = ['x', 'cat', 'dog', 'x', 'dolphin', 'cougar', 'whale']
p ar.chunk{|el| el == 'x'}.each_slice(2).map{|el| el.last.last}
#=> [["cat", "dog"], ["dolphin", "cougar", "whale"]]
Most of the work is chopping off the unneeded side results of the chunk method.
Enumerable#chunk is the way to go. You can use nil to drop those chunks you don't want:
arr = ['x','cat', 'dog', 'x', 'dolphin', 'cougar', 'whale']
arr.chunk{ |e| e != 'x' || nil }.map(&:last)
#=> [["cat", "dog"], ["dolphin", "cougar", "whale"]]
arr.chunk{ |e| true if e != 'x' }.map(&:last) And you could replace true with any truthy.arr.chunk{ |e| e == 'x' ? :_separator : :payload }.map(&:last)Good old Enumerable#reduce is handy for so many things:
def split_array_by_item(array, item)
array.reduce([]) do |memo, x|
memo.push([]) if (x == item) || memo.empty?
memo[-1].push(x) unless x == item
memo
end
end
a = ['x', 'cat', 'dog', 'x', 'dolphin', 'cougar', 'whale']
split_array_by_item(a, 'x') # => [["cat", "dog"], ["dolphin", "cougar", "whale"]]
[Edit] Also:
def split_array_by_item(array, item)
array.chunk{|x|x==item}.reject(&:first).map(&:last)
end
Since Ruby 2.0, a nice solution is slice_before method or since 2.2 slice_when method :
We however need to drop the first element 'x' for each array generated :
ary = ['x', 'cat', 'dog', 'x', 'dolphin', 'cougar', 'whale']
ary.slice_before{|e| e=='x'}.map{|t| t.drop(1)}
#==> [["cat", "dog"], ["dolphin", "cougar", "whale"]]
ary.slice_when{|i,j| j=='x'}.map{|t| t.drop(1)}
#==> [["cat", "dog"], ["dolphin", "cougar", "whale"]]
'x'in a row or it ends on'x'? What's the behavior? Ignore or have an empty[]?