Code:
struct Person {
// define two properties
var name = ""
var age = 0
func birthday(){
age += 1
}
}
// create instance of Person
var person1 = Person()birthday attempts to change the struct from within the struct
so you need to add the prefix mutating :
Code:
struct Person {
struct Person {
// define two properties
var name = ""
var age = 0
mutating func birthday(){
self.age += 1
}
}
// create instance of Person
var person1 = Person()
person1.birthday()
print(person1.age)