How do optionals work in Swift?

How do optionals work in Swift?

Optionals are in the core of Swift and exist since the first version of Swift. An optional value allows us to write clean code with at the same time taking care of possible nil values. If you’re new to Swift you might need to get used to the syntax of adding a question mark to properties.

Why are optionals introduced in Swift?

Swift provides type safety by providing this ‘optional value’. For example, it prevents errors formed from assigning variables of different types. Swift’s optionals provide compile-time check that would prevent some common programming errors happened at run-time.

When should you use optionals Swift?

You use optionals in situations where a value may be absent. An optional represents two possibilities: Either there is a value, and you can unwrap the optional to access that value, or there isn’t a value at all.

What problems do optionals solve Swift?

Swift optionals are a powerful feature in the Swift language which come to solve the problem of non-existing values. They are just a type in Swift language, nothing fancy. They can either contain something or be empty or have no value at all.

How are optionals implemented?

Optionals in Swift are actually much more than a mark at the end of a type, they’re actually an enum. Essentially, Int? is the same thing as Optional , and it’s implemented directly in the enum. You can set them manually with the enum, or you can let the enum do it itself.

What is wrapping and unwrapping in Swift?

Wrapping means the actual value is stored in a logical outer structure. You cannot get to that value (in this case “moo”) without unwrapping it. In Swift world, it is always Christmas, and there are always presents — or at least variables — to unwrap. You unwrap values by adding exclamation points.

How do you use guard let?

in other words, “guard let” is used when the code is 99\% sure of not using the else conditional; in the other hand, “if let” when the code is 50 – 50(example) to use else condition. The variable bound by if let is only visible inside if let scope. The variable bound by guard let is visible afterwards.

Should I always use optionals?

Optional is primarily intended for use as a method return type where there is a clear need to represent “no result,” and where using null is likely to cause errors. You should almost never use it as a field of something or a method parameter.

What are the ways to unwrap optionals in Swift?

Various ways to unwrap an optional in Swift

1. 1,Forced unwrapping — unsafe.
2. 2,Implicitly unwrapped variable declaration — unsafe in many cases.
3. 3,Optional binding — safe.
4. 4,Optional chaining — safe.
5. 5,Nil coalescing operator — safe.
6. 7,Optional pattern — safe.

How do you deal with optionals?

Here’s what you can take away from that:

1. Never force unwrap an optional that’s nil.
2. Always check if an optional is not nil before force unwrapping it.

What happens if you unwrap a non existent optional value?

Please remember that if you force unwrap a nil value, your code will crash. If you’re 100\% sure those values will be valid numbers only – conditionally yes, but if you let the user paste some values or any other scenario – you should check the result using for example if let .

What is forced unwrapping in Swift?

Summary: Forced unwrapping is an action done on the normal Optionals. Implicitly unwrapped Optionals are Optionals, usually used for class initialization and will pass values without exclamation mark when used.

What is an optional value in Swift?

An optional value either contains a value or contains nil to indicate that the value is missing. Write a question mark (?) after the type of a value to mark the value as optional. Why would you want to use an optional value? An optional in Swift is a type that can hold either a value or no value. Optionals are written by appending a? to any type:

How to handle optionals in Swift with if-LET statement?

The if-let statement also automatically unwraps the value and places the unwrapped value in temp constant. This technique has major advantage because you don’t need to forcely unwrap the value although being certain an optional contains a value. 3. Guard statement You can use guard to handle optionals in Swift.

How to show that a different variable is used in Swift?

Here’s some code to demonstrate that a different variable is used: Optional binding works by checking to see if the optional equals nil. If it doesn’t, it unwraps the optional into the provided constant and executes the block. In Xcode 8.3 and later (Swift 3.1), trying to print an optional like this will cause a useless warning.

What is the default value of nil in Swift?

However there is another data type in Swift called Optional, whose default value is a null value ( nil ). You can use optional when you want a variable or constant contain no value in it. An optional type may contain a value or absent a value (a null value).