Here’s my take at clearing up the confusion about the most common type systems used in programming.
I often hear how static and strong typing are used as synonyms. These two are
however quite different systems. The same applies to dynamic and weak typing.
For instance, a programming language can be both dynamically and strongly
typed, but not dynamically and statically. Ruby is an example of a dynamically
and strongly typed language.
Ok, I guess now it’s the time to elaborate.
// example in c# string s = "asdf";
# example in ruby s = "asdf"
# example in ruby "1" + 1 # TypeError
Duck typing is a style of dynamic typing.With duck typing, the set of methods
and properties determine the valid semantics of a class, instead of inheritance
from a specific class or implementation of an interface. “When I see a bird
that walks like a duck and swims like a duck and quacks like a duck, I call
that bird a duck.” This means that we actually don’t care if the class we’re
using is actually of a certain type, as long as it provides the methods or
properties we’re interested in.
The term duck typing comes from python, but ruby is also very known for this behaviour.