Is it generally considered bad practice for a base class constructor to return objects in its derived classes depending on input parameters?

What you're describing is often called a "Factory Method", though typically it'll be named something other than "new".

Consider renaming the "constructor", so that an invocation reads something like   $s = Sentence->from_string("This is a test."); or maybe   $s = Sentence->classify("This is a test."); Update: Technically, a factor method is an instance method that can be overridden. Using a class method for this is similar, but this might be closer to a Factory Function, or maybe a Builder pattern.

In reply to Re: Base class constructor that blesses into subclass by dws
in thread Base class constructor that blesses into subclass by mp

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