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crystal-lang

Crystal lang : `block_given` in Macro?

I want a way to detect whether a block is given to the macro, whose behaviour depends on this.

For methods, I could define two methods to handle the different situation, one with the block argument explicitly and another not. The compiler will call the correct method as expected.

But for macro, I find compiler doesn't care the polymorphism of the block argument -- it always calls the first macro whenever a block is given.

Solution

  • I'm not sure that I understood correctly, but maybe simple check help you?

    macro name(*args, &block)
  {% if block %}
    puts "with block"
  {% else %}
    puts "without block"
  {% end %}
end

name do
  "1"
end
#=> with block

name("1")
#=> without block

    https://carc.in/#/r/53yy