self vs Self

In Swift, self and Self have different meanings and contexts:

1. self: self refers to the instance of the current type within an instance method, computed property, or initializer. It is used to access properties, methods, and other members of the instance. You typically use self to distinguish between instance properties and method parameters that have the same name. For example:

class MyClass {
    var value: Int
 
    init(value: Int) {
        self.value = value
    }
 
    func printValue() {
        print(self.value) // Accessing the instance property using self
    }
}

In the example above, self.value refers to the instance property value of the current object.

2. Self: Self (with a capital “S”) is used to refer to the type of the current class or struct within the definition of that type. It is used when you need to refer to the type itself rather than a specific instance of the type. For example:

class ParentClass {
    func createInstance() -> Self {
        return type(of: self).init()
    }
}
 
class ChildClass: ParentClass {
    var value: Int = 10
 
    required init() {}
 
    func printValue() {
        print(self.value)
    }
}

In this example, Self is used in the createInstance() method of the ParentClass to return an instance of the same type as the class that calls it. This allows subclasses to create instances of their own type.

To summarize, self refers to the current instance of a type, while Self refers to the type itself within the type’s definition.