I have an array with unique elements. Is there a way to replace a certain value in it with another value without using its index value?
Examples:
array = [1,2,3,4]
if array.include? 4
# "replace 4 with 'Z'"
end
array #=> [1,2,3,'Z']
hash = {"One" => [1,2,3,4]}
if hash["One"].include? 4
# "replace 4 with 'Z'"
end
hash #=> {"One" => [1,2,3,'Z']}
p array.map { |x| x == 4 ? 'Z' : x }
# => [1, 2, 3, 'Z']
! to persist the value in the array array.map! { |x| x == 4 ? 'Z' : x }You can do it as:
array[array.index(4)] = "Z"
If the element is not necessarily in the array, then
if i = array.index(4)
array[i] = "Z"
end
You can use Array#map
array = array.map do |e|
if e == 4
'Z'
else
e
end
end
to edit the array in place, rather than creating a new array, use Array#map!
If you have more than one thing you want to replace, you can use a hash to map old to new:
replacements = {
4 => 'Z',
5 => 'five',
}
array = array.map do |e|
replacements.fetch(e, e)
end
This make uses of a feature of Hash#fetch, where if the key is not found, the second argument is used as a default.
hash['key'].map! do |e| ... endA very simple solution that assumes there will be no duplicates and that the order doesn't matter:
hash = { 'One' => [1, 2, 3, 4] }
hash['One'].instance_eval { push 'Z' if delete 4 }
instance_eval sets the value of self to the receiver (in this case, the array [1,2,3,4]) for the duration of the block passed to it.
4 with 'Z', maintaining their original order, and without using any indexes.
hash['One'].instance_eval { push('Z').uniq! if delete 4 } . :)instance_eval does not modify the receiver or its class in any way. The Array class is not modified. All it does is set the value of self to the receiver, and this modification is local to the block passed to it.
array = [1,4,4]; if array.include? 4 # replace 4 with 'Z'?