How to use case when on variable type?

Help & Support
1

I know I’ve seen it somewhere in the doc but I can’t remember where…

BTW, why does the “if” works and the case/when doesn’t ?

a = "hello"

puts typeof(a).class

puts "got it" if typeof(a) == String

case typeof(a)
  when Int32
  puts "hello"
  when String
  puts "bozo"
else
puts "I dunno"
end
2

There’s an example of it in case - Crystal. Just do case a without the typeof.

String == String # => true
String === String # => false

Ultimately it’s because case uses #=== and not #==.

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3

Mmm still a problem : case/in is exhaustive, and I only want to check for some types

4

Use when instead of in like you did above.

case a
when String
  # do string things
  # `a` is constrained to `String` at compile time in this block
when Int32
  # do int things
  # `a` is constrained to `Int32` at compile time in this block
else # this is optional
  # do non-string/int things — `a` is constrained to any of its types
  # *except* String or Int32 here
end
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