Before we talk about handling an error, we need to discuss how we can signal that an error has occurred in the first place. The term for this is throwing an error.
The first part of throwing an error is defining an error that we can throw. Any type can be thrown as an error as long as it implements the ErrorType protocol, as shown:
struct SimpleError: ErrorType {}This protocol doesn't have any requirements, so the type just needs to list it as a protocol it implements. It is now ready to be thrown from a function or method.
Let's define a function that will take a string and repeat it until it is at least a certain length. This will be very simple to implement but there will be a problem scenario. If the passed in string is empty, it will never become longer, no matter how many times we repeat it. In this scenario, we should throw an error.
Any function or method can throw an error as long as it is marked with the...