similar to the one in Ruby
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The following is no longer strictly true with the
Dynamictrait found in [experimental] Scala 2.9. See the answer from Kipton Barros, for example.However,
Dynamicis still not quite likemethod_missing, but rather employs compiler magic to effectively rewrite method calls to “missing” methods, as determined statically, to a proxy (applyDynamic). It is the approach of statically-determining the “missing” methods that differentiates it frommethod_missingfrom a polymorphism viewpoint: one would need to try and dynamically forward (e.g. with reflection) methods to get truemethod_missingbehavior. (Of course this can be avoided by avoiding sub-types 🙂No. Such a concept does not exist in Java or Scala.
Like Java, all the methods in Scala are ‘bound’ at compile time (this also determines what method is used for overloading, etc). If a program does compile, said method exists (or did according to the compiler), otherwise it does not. This is why you can get the NoSuchMethodError if you change a class definition without rebuilding all affected classes.
If you are just worried about trying to call a method on an object which conforms to a signature (“typed duck typing”), then perhaps you may be able to get away with structural typing. Structural typing in Scala is magical access over reflection — thus it defers the ‘binding’ until runtime and a runtime error may be generated. Unlike method_missing this does not allow the target to handle the error, but it does allow the caller to (and the caller could theoretically call a defined methodMissing method on the target… but this is probably not the best way to approach Scala. Scala is not Ruby 🙂