Ruby Syntax: How to write "a = h[:v] if !h[:v].nil?"

Question

I find myself often writing statements equivalent to:

deleted_at = Time.at(data[:deleted_at]) if !data[:deleted_at].nil?

i'd like to be able to write this in a more concise way. Any suggestions?

Sometimes I write this as:

deleted_at = Time.at(i) if !(i = data[:deleted_at]).nil?

But I think this makes the code harder to read so I hope there is some nicer way to do this.

Answer 1

I use 'unless' since I find it more readable:

deleted_at = Time.at(data[:deleted_at]) unless data[:deleted_at].nil?

or you could even use:

deleted_at = Time.at(data[:deleted_at]) if data[:deleted_at]

Answer 2

You could wrap that generically into a lambda block:

class Object
  def unless_nil?
    yield self unless self.nil?
  end
end

data[:deleted_at].unless_nil? {|i| deleted_at = i }

I'd recommend to not monkey patch the Object class but better create a module and include that in the classes you need this functionality for.

Answer 3

You can also do

data[:deleted_at] and deleted_at = Time.at(data[:deleted_at])

although whether that's better is a matter of taste.

Answer 4

Not having deleted_at declared like that is not my cup of tea. It would at least be set to nil with something like this:

deleted_at = Time.at(data[:deleted_at]) rescue nil

or

deleted_at = data[:deleted_at].nil? ? nil : Time.at(data[:deleted_at])

Answer 5

data_deleted = data[:deleted_at]
deleted_at = Time.at(data_deleted) unless data_deleted.nil?

makes it more readable IMO.

Answer 6

You can take advantage of the nil version evaluating to false to do this:

deleted_at = data[:deleted_at] and Time.at(data[:deleted_at])

Although now having written this i think i prefer the if version.

Code is written far less than its read - concise doesn't always equate to readable.

Answer 7

If it's only Time.at that's giving you problems, you could write

class Time
  def nil_friendly_at(time)
    return nil if time.nil? # Or "unless time"
    at(time)
  end
end

Or you could monkey-patch Time.at itself if you want (I'm not recommending this though!)