Why we need to use init method explicitly while we can create an object without it
class Details {
}
var obj = Details()
var obj = Details.init()
What's the difference between these two instance creations
Both are allowed and are equivalent. As The Swift Programming Language says:
If you specify a type by name, you can access the type’s initializer without using an initializer expression. In all other cases, you must use an initializer expression.
let s1 = SomeType.init(data: 3) // Valid let s2 = SomeType(data: 1) // Also valid let s3 = type(of: someValue).init(data: 7) // Valid let s4 = type(of: someValue)(data: 5) // Error
So, when you’re supplying the name of the type when instantiating it, you can either use the SomeType(data: 3) syntax or SomeType.init(data: 3). Most Swift developers would favor SomeType(data: 3) as we generally favor brevity unless the more verbose syntax lends greater clarity, which it doesn’t in this case. That having been said, SomeType.init(data: 3) is permitted, though it is less common in practice.
Class() is just a shorthand for Class.init()
Both are interpreted by the compiler as exactly the same statements with no difference at all.