How Do I Write If Case Let in Swift?

if case let is an abbreviated form of switch

case let immediately precedes the candidate pattern in both versions. Confusingly though, when using if case let, the value comes after the = operator. So

if case let Puppy.mastiff(droolRating, weight) = fido {

is equivalent to:

switch fido {
case let Puppy.mastiff(droolRating, weight):

// tell fido he's a good doggo

let binds associated values

case let is a shortcut that lets you bind all subsequent associated values with just variable names. But you can write each let individually, just before the variable name:

if case Puppy.mastiff(let droolRating, let weight) = fido {

// does that pup need an extra treat?

Provide a single name to create a tuple of all associated values at once:

if case let Puppy.mastiff(characteristics) = fido {

// how cute is this doggo, exactly?

The ? is syntactic sugar to only match non-nil optionals:

if case let Puppy.mastiff(droolFactor, weight)? = potentialPup {

// oh thank goodness, a puppy

Omit let entirely if you don't need the associated values:

if case Puppy.mastiff = fido {

// just hand me the pupster

Add conditions to if and guard using commas

if case let Puppy.mastiff(droolRating, _) = fido, droolRating > 8 {

// you're going to need a new couch
guard case let Puppy.mastiff(droolRating, _) = fido, droolRating < 10 else {

// that dog is not coming in the house

Iterate using for, where and logical operators

for case let Puppy.mastiff(droolRating, weight) in rescuePups where droolRating > 5 && weight > 15.0 {

// I'll take the chubby, soggy ones please

Use ? to iterate over just non-optional values, even when doubly nested in associated values:

for case let SocialMedia.instagram(linkInBio?)? in\.socialMedia) {

// all the links please

Bind non-optional derived values in chained expressions

Really helpful if you need one non-optional assignment amidst a bunch of optional ones:

if let rescueCenter = nearest(), case let puppies = rescueCenter.puppies, puppies.count < 10 {

// better hurry or might not get enough

Other more in-depth articles:

  • Swift Pattern Matching In Detail - Benedikt Terhechte
  • Pattern Matching In Swift - Ole Begemann
  • Pattern Matching - Crunchy Development
  • Pro Pattern-Matching in Swift - Nick Teissler, Big Nerd Ranch
  • Using the power of switching with associated values to write elegant, logical, meaningful code -