How can we comprehend the concept of mutating methods in Swift structs?

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In Swift, a mutating method is a function that can modify the properties of a struct or an enum. Structs and enums are value types in Swift, which means that when they are passed around, they are copied. Therefore, if we want to modify the properties of a struct or an enum, we need to use the mutating keyword to make it clear that this method changes the original value, not a copy of it.

For instance, consider the following struct:

struct Person {
   var name: String

   mutating func changeName(to newName: String) {
     name = newName
   }
}

In the above code, the struct Person has a property name, and a mutating method changeName(to:) that takes a String parameter newName and changes the value of the name property to newName.

When we create a variable person of type Person, we can call the method changeName(to:) to modify the value of the name property:

var person = Person(name: "John")
person.changeName(to: "Mike")

After calling the changeName(to:) method, the value of the name property of the person variable will be "Mike".

In summary, mutating methods in Swift structs allow us to modify the properties of a struct or an enum, and the use of the mutating keyword makes it clear that the method changes the original value, not a copy of it.