How to create a validation in Rails that checks if a string contains only emoji characters?

Question

I need to check if the given string is using Unicode emojis only (). What would be the possible solution?

Answer 1

Matching a comprehensive set of emoji is difficult. You can either use a set of regular expressions to look for 'emoji-like' things, you can somewhere mark all emoji with special characters for start/end, or you can make a list of all possible emoji and match against it.You likely want to use some kind of regular expression.

If you want to use a regular expression, you can use the active record "match"

class Emoji < ActiveRecord::Base
  validates :something, format: { with: /[:;][\)3\/|\(]/,
    message: "only allows emojis" }
end

I might have escaped a few things there that ruby doesn't require escaping, but you get the idea. That regular expression will match one of : or ; and then one of ), (, /, or | which fit together to make a face. However lots of emoji can be more complicated. This next example compares the string with a list of valid emoji that you have in listOfEmoji. It uses the inclusion validator.

class Emoji < ActiveRecord::Base
  validates :something, inclusion: { in: listOfEmoji,
    message: "%{value} is not in the list of valid emoji" }
end

Finally, you might escape the start and end of anything that earlier in the code you identified as emoji. You'd have to use something that wouldn't be included in an actual emoji to do this, and then match it as a regular expression. for example, if you replace :) with emoji:)endemoji you could validate it with a regular expression like this:

class Emoji < ActiveRecord::Base
  validates :something, format: { with: /emoji.+endemoji/,
    message: "only allows emojis" }
end

.+ is the regular expression for (any character) 1 or more times. so that would match a special signal that your code would wrap what it knows is an emoji with that you could later use to identify an emoji. There are better words to use than emoji, endemoji though. My favorite is the ascii 7, the character for a typewriter bell!

All of these are possibilities and the best answer depends a lot on how you want to build your code and what you're trying to do.