What is the rationale behind Array === Array (or indeed any other class) being
false? Array.new === Array is also false. How do I test what class some
object is in a case statement?
Tim Bates
Tim Bates wrote:
What is the rationale behind Array === Array (or indeed any other class) being
false?
It’s the case equality operator. The Array class object isn’t a case of
Array, its a case of Class.
Array.new === Array is also false.
Array === Array.new #=> true
How do I test what class some
object is in a case statement?
The case statement reverses the order of the call when calling the ===.
case Array.new
when Array
puts “I’m an Array”
end
outputs “I’m an Array”
···
–
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irb(main):001:0> a =
irb(main):002:0> case a
irb(main):003:1> when Array
irb(main):004:1> puts “Array”
irb(main):005:1> when Hash
irb(main):006:1> puts “Hash”
irb(main):007:1> end
Array
nil
ie, in
case a
when B
…
when C
…
end
the comparison being done is B === a, not a === B.
It just makes sense that
irb(main):008:0> Array === Array.new
true
And of course
irb(main):009:0> Array === Array
false
because Array is not an instance of class Array but of class Class
irb(main):010:0> Class === Array
true
···
On Mon, Dec 02, 2002 at 07:20:05PM +0900, Tim Bates wrote:
What is the rationale behind Array === Array (or indeed any other class) being
false? Array.new === Array is also false. How do I test what class some
object is in a case statement?
–
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