What is the meaning of question mark "?" in Swift?

Swift - Interview Questions

In Swift, question mark "?" is used in property declaration. It tells the compiler that this property is optional. The property may hold a value or not. It avoids runtime errors when accessing that property by using ?. This is useful in optional chaining and a variant of this example is in conditional clauses.

Syntax :

var optionalName : String? = "Chanti"  
if optionalName != nil {  
    print("Your name is \(optionalName!)")  
}