Declaring an array in Ruby is simple:
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ary = ["foo", "bar"]
# => ["foo", "bar"]However, did you know you can save the array elements as variables the exact same time you declare them?
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ary = [
foo = "foo",
bar = "bar"
]
foo # => "foo"
bar # => "bar"Looking like some magic? Well, it is not magic 🙂. This happens because assigning a value to a variable is an expression in Ruby. This is applicable to many other cases, like assigning a value on a conditional :
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if user = User.find(params[:id])
puts "User is #{user.name}"
endOr even crazier: to save the parameter you pass to a method!
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def some_method(arg)
puts arg
end
some_method(value = "Hola")
# prints -> "Hola"
value
# => "Hola"Disclaimer: ☝️ those 2 might be bad ideas. I wouldn't use it regularly on any code I write but knowing it is possible is always a good thing.
What can I apply this?
It plays quite well with constants that can then be used as some kind of enums:
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COLORS = [
COLOR_RED = "RED",
COLOR_BLUE = "BLUE",
COLOR_GREEN = "GREEN",
COLOR_YELLOW = "YELLOW"
]
# => ["RED", "BLUE", "GREEN", "YELLOW"]On rails apps they are especially useful to declare scopes:
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scope :non_red, -> { where(color: COLORS - [COLOR_RED]) }
scope :blue, -> { where(color: COLOR_BLUE) }Pretty cool, right? This is the first post in a four part series of Ruby tricks. Feel free to check the rest out.