Optional Types

Optional represents either wrapped value or nil.
Optionals are generic enum type that works as wrapper.

Basically wrapper allow variable have 2 states:

1. User define type
2. nil (that represent no value)

In swift nil value must be optional.
Optional can be created by appending either "?" or "!".

example :

var name : String? = nil

var lname : String! = nil

"?" must be explicitly unwrapped where as "!" automatically unwrapped.

Conditionally unwrapped use "?" optional binding where as force unwrapped use "!" operator. If you force unwrapped variable and value is nil then program will throw exception and crash so be careful.

example :

var lname : String! = nil

print(lname!)

Output :

fatal error: unexpectedly found nil while unwrapping an Optional value

Safe unwrapping :

Using if-let statement safe unwrap

example :

func safeUnwrap(withName name : String?){

    if let userName = name{

        print(userName)

    }else{

        print("name value is nil")

    }

}

safeUnwrap(withName: "Pratik")

Output :

Pratik

safeUnwrap(withName: nil)

Output :

name value is nil

Using guard-let statement safe unwrap

example :

func safeUnwrap(withName name : String?){

    guard let userName = name else{

        print("user name not found")

        return

    }

    print(userName)

}

safeUnwrap(withName: "Pratik")

Output :

Pratik

safeUnwrap(withName: nil)

Output :

user name not found

Using Coalescing operator safe unwrap

example :

var name : String? = nil

print(name ?? "name value is nil")

Output :

name value is nil

var name : String? = nil

name = "Pratik"

print(name ?? "name value is nil")

Output :

Pratik

You can also use Optional chaining in order to call method,property or subscript.

example : 

struct Family{

    func printName() {

        print("Hello friends")

    }

}

var objFamily : Family?

objFamily?.printName()

Output :

no print 

var objFamily : Family? = Family()

objFamily?.printName()

Output :

Hello friends

Optional types unwrapped

Logger

Hello friends this article is use for developer debugging print values in LLDB debug area.

There are multiple functions available in swift

print(),debugPrint(),dump(),NSLog()

use of these functions in swift

print : print(_ items: Any..., separator: String = default, terminator: String = default)

print is use for some textual representations in debug area. 

example : 

print("hello friends")

Output : 

hello friends

debugPrint : debugPrint(_ items: Any..., separator: String = default, terminator: String = default)

debugPrint is use for shows the instance of some textual representations in debug area.

example : 

debugPrint("hello friends")

Output : 

"hello friends"

dump : dump<T>(_ value: T, name: String? = default, indent: Int = default, maxDepth: Int = default, maxItems: Int = default)

dump is use for print the contents of an object via reflection like mirroring. dump prints details hierarchy. 

example : 

dump(["iOS","Android"])

Output : 

▿ 2 elements

  - "iOS"

  - "Android"

NSLog : NSLog(_ format: String, _ args: CVarArg...)

NSLog is use for print the contents with timestamp. It will also print project_name along with timestamp.

example :

NSLog("hello iOS developers")

Output : 

2018-09-17 15:18:10.522 DebuggerDemo[2022:4583274]hello iOS developers

print() vs dump()

Let’s create simple “Student” class

class Student{

    let name = "Pratik"

    let lname = "Lad"

}

now print Student() class using print() & dump() 

print(Student())

Output :

__lldb_expr_81.Student

dump(Student())

Output : 

▿ __lldb_expr_81.Student #0

  - name: "Pratik"

  - lname: "Lad"

You can see the difference of printing in debug area result. print() simple print the class name where as dump() print the whole class hierarchy.