How does let x where x.hasSuffix(“pepper”) work

Question

In the code block below, I am having trouble understanding let x where x.hasSuffix(\"pepper\").

let vegetable = \"red pepper\"

switch vegetable {
          


        

Answer 1

vegetable is an implicit String. It's the same as you would write:

var vegetable: String = "red pepper"

hasSuffix is declared as func hasSuffix(suffix: String) -> Bool an therefore returns a Bool. The where keyword specifies additional requirements, and can only be used in switch statements.
Because all of this is suffused, the vegetable variable is assigned to x (let x).

You can read more about the where and switch here.

Answer 2

There is actually no reason to use let x in this scenario. case let x where x.hasSuffix("pepper"): can simply be replaced with case vegetable where vegetable.hasSuffix("pepper"). In this scenario, an extra variable x is declared which copies vegetable. This is useless, and arguable reduces readability, even if you renamed x to vegetable as well.

Using let in a switch statement case is useful in other cases, such as when the "argument" (vegetable) is not a variable, e.g. switch(getVegetableName()) , or in the case where the "argument" is a tuple, and needs to be unpacked, such as in

let vegetableNameAndCountry = ("Sweet Potato", "United States")

switch(vegetableNameAndCountry) {
   case (let vegetable, let country) where country == "Tanzania":
       print("This \(vegetable) comes from a country north of Kenya")
   case ("Sweet Potato", _): // Note here I ignore the country, and don't even bother creating a constant for it
       print("Sweet sweet potatoes")
   default:
       print("We don't care about this vegetable")
}