[ruby] How do I remove blank elements from an array?

I have the following array

cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"]

I want to remove blank elements from the array and want the following result:

cities = ["Kathmandu", "Pokhara", "Dharan", "Butwal"]

Is there any method like compact that will do it without loops?

There are already a lot of answers but here is another approach if you're in the Rails world:

 cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"].select &:present?

Here is a solution if you have mixed types in your array:

[nil,"some string here","",4,3,2]

Solution:

[nil,"some string here","",4,3,2].compact.reject{|r| r.empty? if r.class == String}

Output:

=> ["some string here", 4, 3, 2]

When I want to tidy up an array like this I use:

["Kathmandu", "Pokhara", "", "Dharan", "Butwal"] - ["", nil]

This will remove all blank or nil elements.

Most Explicit

cities.delete_if(&:blank?)

This will remove both nil values and empty string ("") values.

For example:

cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal", nil]

cities.delete_if(&:blank?)
# => ["Kathmandu", "Pokhara", "Dharan", "Butwal"]

 cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"].delete_if {|c| c.empty? } 

Try this:

puts ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"] - [""]

Shortest way cities.select(&:present?)

Update with a strict with join & split

cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"]
cities.join(' ').split

Result will be:

["Kathmandu", "Pokhara", "Dharan", "Butwal"]

Note that: this doesn't work with a city with spaces

In my project I use delete:

cities.delete("")

Use reject:

>> cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"].reject{ |e| e.empty? }
=> ["Kathmandu", "Pokhara", "Dharan", "Butwal"]

Here is one more approach to achieve this

we can use presence with select

cities = ["Kathmandu", "Pokhara", "", "Dharan", nil, "Butwal"]

cities.select(&:presence)

["Kathmandu", "Pokhara", "Dharan", "Butwal"]

You can Try this

 cities.reject!(&:empty?)

Plain Ruby:

values = [1,2,3, " ", "", "", nil] - ["", " ", nil]
puts values # [1,2,3]

another method:

> ["a","b","c","","","f","g"].keep_if{|some| some.present?}
=> ["a","b","c","f","g"]

Here is what works for me:

[1, "", 2, "hello", nil].reject(&:blank?)

output:

[1, 2, "hello"]

To remove nil values do:

 ['a', nil, 'b'].compact  ## o/p =>  ["a", "b"]

To remove empty strings:

   ['a', 'b', ''].select{ |a| !a.empty? } ## o/p => ["a", "b"]

To remove both nil and empty strings:

['a', nil, 'b', ''].select{ |a| a.present? }  ## o/p => ["a", "b"]

cities.reject! { |c| c.blank? }

The reason you want to use blank? over empty? is that blank recognizes nil, empty strings, and white space. For example:

cities = ["Kathmandu", "Pokhara", " ", nil, "", "Dharan", "Butwal"].reject { |c| c.blank? }

would still return:

["Kathmandu", "Pokhara", "Dharan", "Butwal"]

And calling empty? on " " will return false, which you probably want to be true.

Note: blank? is only accessible through Rails, Ruby only supports empty?.

compact_blank (Rails 6.1+)

If you are using Rails (or a standalone ActiveSupport), starting from version 6.1, there is a compact_blank method which removes blank values from arrays.

It uses Object#blank? under the hood for determining if an item is blank.

["Kathmandu", "Pokhara", "", "Dharan", nil, "Butwal"].compact_blank
# => ["Kathmandu", "Pokhara", "Dharan", "Butwal"]

[1, "", nil, 2, " ", [], {}, false, true].compact_blank
# => [1, 2, true]

Here is a link to the docs and a link to the relative PR.

A destructive variant is also available. See Array#compact_blank!.

If you need to remove only nil values,

please, consider using Ruby build-in Array#compact and Array#compact! methods.

["a", nil, "b", nil, "c", nil].compact
# => ["a", "b", "c"]

1.9.3p194 :001 > ["", "A", "B", "C", ""].reject(&:empty?)

=> ["A", "B", "C"]