Filter By Type

In Ruby, we have several ways to check if something is a certain type (class or subclass). A couple common approaches you might see are #is_a? and === (case equality operator):

> 3.is_a?(Integer)
=> true
> Integer === 3
=> true
> 3 === Integer
=> false

Notice it is important to get the ordering of class and value right when using ===.

We can use these concepts to filter collections down to just those values of a certain type. We can also ditch those methods and instead use #grep to pattern match on the type directly.

> nums = [1, :two, 3.0, 'four', 5, -> { 6 }, 0.7]
=> [1, :two, 3.0, "four", 5, #<Proc:0x0000000123af0338 (irb):5 (lambda)>, 0.7]
> nums.filter { it.is_a?(Numeric) }
=> [1, 3.0, 5, 0.7]
> nums.filter { Integer === it }
=> [1, 5]
> nums.grep(Integer)
=> [1, 5]
> nums.grep(Numeric)
=> [1, 3.0, 5, 0.7]

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