> This one struck me. Today the public methods of a class would check to make sure the inputs are valid. Back then the programmer would just know the location o

> This one struck me. Today the public methods of a class would check to make sure the inputs are valid. Back then the programmer would just know the location of every single caller and make sure the calls are always valid in the first place. Personally, I would use the second option even today, with the caveat that there should be few, if any invalid inputs, what with type systems and OOP. If your method takes a string as a parameter, and can't handle every string that ever existed, then you really should be deserializing it into a data object of some kind, so that the compiler does the validation for you. If I'm developing some kind of API for public consumption, then I'll do input validation at the service boundary so that the consumer knows why it didn't work, but otherwise I'm a big proponent of the "just don't pass null" approach. Input validation on every function call bloats the code base, and is annoying to read through.