Ditch That Else (preslav.me)

Great advice. This is probably one of the top 5 or 10 things an inexperienced programmer could adopt to level up.

If possible, also ditch that if.

Swift replaces it by guard. I’m not a 100% fan of its syntax (1), which is

    guard <#condition#> else {
       <#statements#>
    }

but do like that <#statements#> must return. So, guard… else semantically can be replaced by if !, but is a bit more limited, thus making it easier to recognize the pattern.

https://docs.swift.org/swift-book/documentation/the-swift-pr...:

“The else clause of a guard statement is required, and must either call a function with the Never return type or transfer program control outside the guard statement’s enclosing scope using one of the following statements:

- return

- break

- continue

- throw”

(1) I can’t think of a much better one, but think I would have picked

    requires <#condition#> else {
       <#statements#>
    }

or (getting rid of that weird else):

    ifnot <#condition#> {
       <#statements#>
    }

Eiffel’s preconditions (https://www.eiffel.org/doc/eiffelstudio/Precondition) look even nicer:

    require <#condition#>

but do not allow specifications of what to do when the condition isn’t met, and aren’t supposed to be checked in procession code. https://www.eiffel.org/doc/eiffel/ET-_Design_by_Contract_%28...:

“It is in fact part of the Eiffel method that a routine body should never test for the precondition, since it is the client's responsibility to ensure it. (An apparent paradox of Design by Contract™, which is reflected in the bottom-right entries of the preceding and following contract tables, and should not be a paradox any more at the end of this discussion, is that one can get more reliable software by having fewer explicit checks in the software text.)”