How do I remove blank elements from an array?
RubyArraysRuby Problem Overview
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?
Ruby Solutions
Solution 1 - Ruby
There are many ways to do this, one is reject
noEmptyCities = cities.reject { |c| c.empty? }
You can also use reject!, which will modify cities in place. It will either return cities as its return value if it rejected something, or nil if no rejections are made. That can be a gotcha if you're not careful (thanks to ninja08 for pointing this out in the comments).
Solution 2 - Ruby
1.9.3p194 :001 > ["", "A", "B", "C", ""].reject(&:empty?)
=> ["A", "B", "C"]
Solution 3 - Ruby
Here is what works for me:
[1, "", 2, "hello", nil].reject(&:blank?)
output:
[1, 2, "hello"]
Solution 4 - Ruby
In my project I use delete:
cities.delete("")
Solution 5 - Ruby
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.
Solution 6 - Ruby
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"]
Solution 7 - Ruby
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"]
Solution 8 - Ruby
Try this:
puts ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"] - [""]
Solution 9 - Ruby
Use reject:
>> cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"].reject{ |e| e.empty? }
=> ["Kathmandu", "Pokhara", "Dharan", "Butwal"]
Solution 10 - Ruby
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?.
Solution 11 - Ruby
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?
Solution 12 - Ruby
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"]
Solution 13 - Ruby
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]
Solution 14 - Ruby
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"]
Solution 15 - Ruby
You can Try this
cities.reject!(&:empty?)
Solution 16 - Ruby
cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"].delete_if {|c| c.empty? }
Solution 17 - Ruby
Shortest way cities.select(&:present?)
Solution 18 - Ruby
another method:
> ["a","b","c","","","f","g"].keep_if{|some| some.present?}
=> ["a","b","c","f","g"]
Solution 19 - Ruby
Update in reject and reject!
> NOTE: I can across this question a check these methods on the irb console with ruby-3.0.1. I also checked the ruby docs but this is not mentioned there. I am not sure from which ruby version this
> change is there. Any help from the community is much appriciated.
With ruby-3.0.1 we can use either reject or reject!
cities = ["Kathmandu", "Pokhara", "", "Dharan", "Butwal"]
cities.reject{ |e| e.empty? }
=> ["Kathmandu", "Pokhara", "Dharan", "Butwal"]
or shorthand
cities.reject(&:empty?)
=> ["Kathmandu", "Pokhara", "Dharan", "Butwal"]
both will return [] no matter we have an empty value or not?
Solution 20 - Ruby
Plain Ruby:
values = [1,2,3, " ", "", "", nil] - ["", " ", nil]
puts values # [1,2,3]
Solution 21 - Ruby
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