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    <p>While I respect Cedric, he's completely wrong on this issue. Scala's pattern matching can be fully-encapsulated from class changes when desired. While it is true that a change to a <em>case class</em> would require changing any corresponding pattern matching instances, this is only when using such classes in a naive fashion.</p> <p>Scala's pattern matching <em>always</em> delegates to the deconstructor of a class's companion object. With a case class, this deconstructor is automatically generated (along with a factory method in the companion object), though it is still possible to override this auto-generated version. At all times, you can assert complete control over the pattern matching process, insulating any patterns from potential changes in the class itself. Thus, pattern matching is simply another way of accessing class data through the safe filter of encapsulation, just like any other method.</p> <p>So, Dr. Odersky's opinion would be the one to trust here, particularly given the sheer volume of research he has performed in the area of object-oriented programming and design.</p> <p>As for where it should be used, that is entirely according to taste. If it makes your code more concise and maintainable, use it! Otherwise, don't. For most object-oriented programs, pattern matching is unnecessary. However, once you begin to integrate more functional idioms (<code>Option</code>, <code>List</code>, etc) I think you'll find that pattern matching will significantly reduce syntactic overhead as well as improving the safety offered by the type system. In general, any time you want to extract data while simultaneously testing some condition (e.g. extracting a value from <code>Some</code>), pattern matching will likely be of use.</p>
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    1. USDaniel Spiewak
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