Examining interfaces

If you read a textbook on a traditional language such as Java or C#, you will see that interfaces are often referred to as contracts. When you opt to use an interface, you are telling CODESYS that you agree to, at the very least, implement all the methods prototyped in the interface. However, in my opinion, this is a little confusing.

Generally, when I describe an interface to a new programmer, I usually describe them as a model for something. For example, if we are building an airplane, we will need certain things such as wings, an engine, and a cockpit regardless of whether we are building a prop plane or an F-35 jet fighter. Obviously, for each type of plane, these parts are going to be different. As such, when we implement an interface, we are telling our function block that we are going to use the methods that are declared in the interface but those methods may have different implementations.

To demonstrate how an interface works, let’s implement...