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24 Oct 2024

Property wrappers provide a way to add behaviors like validation, transformation, or default values to properties without repeating the same code elsewhere.

Let’s take an example where we can use property wrapper for performing a transformation on a value. We will create a @Capitalized property wrapper that automatically capitalizes any string assigned to a property:

@propertyWrapper
struct Capitalized {
    private var value: String = ""
    
    var wrappedValue: String {
        get { value }
        set { value = newValue.capitalized }
    }
}

The setter in the above example takes the incoming value and capitalizes it and assigns it to the value property. The getter, as we can see then provides the capitalized value.

You can now use @Capitalized to automatically capitalize user input:

struct User {
    @Capitalized var name: String
}

var user = User()
user.name = "john appleseed"
print(user.name) // Code Prints: John Appleseed

As we can see, in the above example the name gets capitalized everytime behind the scenes when the name is set.