Swift Optional

Some people found it very confusing initially but when you will understand then it is simple. As we know optional tells itself about it. It's two cases.
  • The first case when a value can be present for a type, then we need to unwrap if need to use it.
  • Second case when a value can not be present for a type.
We use '?' to mark a value as optional.

class Student {
    var name:String? //  name becomes optional
}

When you declare the name string as optional by marking '?' then it's valued automatically is set to nil. 

NOTE: Swift 'nil' is not same as objective c 'nil'. In Objective-C, it is a pointer to an object which does not exist whereas in swift it's just an absence of a value for a type.

let person = Student()
print(person.name)

When you access the name it will print a nil. As there is no value assigned to name.
Once we will provide a value to name, let say, "Swift". Then it looks like.

class Student {
        var name:String? = "swift"
}

Now accessing the value of name using:

let person = Student()
print(person.name)

Will print the optional value. It will be like Optional("swift"). It's not the same as string "swift". It's type Optional and if you need to have this value then you use "Forced Unwrapping". Using '!', to read the optional value. But It's not recommended to use "!" to read an underlying value of Optional type it could be costly when the optional type does not have a value. Then it will crash your app. You can use whenever you want but you have to sure that Optional type has underlying value.

let person = Student()
print(person.name!) // will print "swift"

There are other ways to access the underlying value of optional type.
1 - Using If condition along with Forced Unwrapping: Use if condition to make sure, it has underlying value and reading using forced unwrapping '!'.

if person.name != nil {
        print(person.name!) // print "swift"
}

2- Using Optional Binding: You can use Optional binding to read the underlying optional value. You can access it and store it constant or variable type. Optional binding can be used with the "if" and "while".

if let temp = person.name {
        print(temp) // print "swift"
}

Optional binding is a safe way to handle optional. It won't make your app crash if the optional type does not have any value.
Hope I am able to make understand y'all. Please do comment and give your valuable feedback. 

Location: Bengaluru, Karnataka, India

Comments

Post a Comment

Popular posts from this blog

How to Disable iOS/iPad App availability on Mac Store, Silicon?

Image
As we all know that iPhone and iPad apps will be available on Mac App Store on Apple silicon. So if you are willing not to serve on Mac App Store we need to do some changes to  our deployed builds. As we know this is going to happen automatically on Apple Silicon Mac for all your iOS/iPad App. Though there will be no modification on the App.  Thank God !! There is no extra work for porting to the Mac App.   Do not worry about the framework and all they will work just fine as they were working on the iPhone and iPad, the framework will be intact as it is. So Happy 😊 How we can identify the app on the Mac App Store, Users will be able to find iPhone and iPad apps right on the Mac App Store. These apps will be distinguished by the “ Designed for iPhone ” and “ Designed for iPad ” badge next to the app icon. You should not worry about the rating and review as well those will be independently mapped. Managing Mac App Store availability.   By default, your apps will be pub
Read more

Copy Vs Mutable Copy in iOS

It's found very confusing for most of the folks, who is not having much experience in Objective-C. Before starting I just to say: Just remember below lines- 1 - copy always creates an immutable copy means you can not modify the object. 2 - mutableCopy always creates a mutable copy  means you can modify the object Here onwards I try to explain copy and mutable copy with some examples: copy: NSArray *obj = [ NSArray arrayWithObjects : @"1" , @"2" , nil ]; NSArray *copyObj = [obj copy ]; NSArray *mutableObj = [obj mutableCopy ]; When you try to see the details of copyObj its clearly shows  __NSArrayI which tells that you can not modify this object Printing description of copyObjy: <__nsarrayi 0x6080000238a0="">( 1, 2 ) Same way  When you try to see the details of mutableObj its clearly shows  __NSArrayM which tells that you can modify this object Printing description of mutableObjy: <__nsarr
Read more

Functions in Swfit 3.0

As you have seen the previous post on Protocol , NSBlockOperation , Range Operators , Extension . Here you go with the new topic as Function in Swift 3.0.1 with Xcode 8.1. It will include detailed explanation about it. According to Apple’s  Swift Programming Language Book : Methods are functions that are associated with a particular type. Classes, structures, and enumerations can all define instance methods, which encapsulate specific tasks and functionality for working with an instance of a given type. Classes, structures, and enumerations can also define type methods, which are associated with the type itself. Type methods are similar to class methods in Objective-C. Functions A function contains some lines code which performs a specific task. You need to a name function, which explains what it does, call it whenever you need it. Defining and Calling Functions: Defining function -  func wishBday ( person : String ) -> String { let wishes = "
Read more