CODEWITHSUNDEEP
ruby
Mike
Mike

Reputation: 45

Can I use a ternary operator with only one result?

Will I run into any problems using a statement like this:

options[:discount] ? "Does something if true" : nil

Instead of:

"Do something if true" if options[:discount]

I'm not sure I would actually use the former syntax, but I am interested if returning nil in such a statement would cause any issues. Just trying to learn more about Ruby's structure and this was an interesting question to me. Thanks for any insight!

Upvotes: 1

Views: 864

Answers (2)

user12341234
user12341234

Reputation: 7223

One difference is the precedence of those two operators. Consider the following:

options = {discount: false}
prexisting_value = "prexisting value"

using the first expression, you get this:

prexisting_value = options[:discount] ? "Does something if true" : nil
p prexisting_value
=> nil

using the second expression, you get this:

prexisting_value = "Do something if true" if options[:discount]
p prexisting_value
=> "prexisting_value"

this happens because the two examples are parsed differently (note the location of the parenthesis):

prexisting_value = (options[:discount] ? "Does something if true" : nil)

vs

(prexisting_value = "Do something if true") if options[:discount]

Upvotes: 1

knut
knut

Reputation: 27885

It may depend how you use it.

Let's try it with 

options = {
  :discount => true
}

x = options[:discount] ? "Does something if true" : nil
y = "Do something if true" if options[:discount] 

p x
p y

and you get 

"Does something if true"
"Do something if true"

With the false-value, you get two times nil.

If you want to print the result immediate, without an additional variable like in

p options[:discount] ? "Does something if true" : nil
p "Do something if true" if options[:discount]

you get the same result for true, but with falseyou get only one nil.The if-clause is used for the complete expression p "Do something if true".

Or another example:

You can use the ternary operator as a parameter:

def my_method(par)
  p par
end
my_method(options[:discount] ? "Does something if true" : nil)

but you get syntax error, unexpected modifier_if, expecting ')' with

my_method("Do something if true" if options[:discount])

You can use the if with two braces:

my_method(("Do something if true" if options[:discount]))

or you use

my_method(if options[:discount]; "Do something if true";end )

Upvotes: 3

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