If a type defines a
to_unsafe method, when passing it to C the value returned by this method will be passed. For example:
lib C fun exit(status : Int32) : NoReturn end class IntWrapper def initialize(@value) end def to_unsafe @value end end wrapper = IntWrapper.new(1) C.exit(wrapper) # wrapper is not an Int32, but its to_unsafe # method is, so wrapper.to_unsafe # is passed instead
This is very useful for defining wrappers of C types without having to explicitly transform them to their wrapped values.
For example, the
String class implements
to_unsafe to return
lib C fun printf(format : UInt8*, ...) : Int32 end a = 1 b = 2 C.printf "%d + %d = %d\n", a, b, a + b
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