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: Before you open it (or “unwrap” in the language of optionals) you won't know if it contains something or nothing..
Furthermore, why do we use optionals in Swift?
You use optionals: For properties that have no initial value (and no initial value set in a constructor), such as certain outlet properties. You also can create a property that's not vital to the functioning of a certain instance, i.e. optional. When a method that's supposed to return a value fails.
Beside above, what is nil in Swift? nil is described in the Apple docs as: meaning “the absence of a valid object.” If you're new to programming nil simply means that a variable (sometimes called an object) is empty and has no value assigned. If you have a background in programming nil can be thought of best as a like-for-like replacement for null .
Regarding this, how do I unwrap optionals in Swift?
You can unwrap optionals in three-and-a-half ways: With force unwrapping, using if [optional] != nil and [optional]! With optional binding, using if let [non-optional] = [optional] {
What is tuple in Swift?
Tuples in Swift occupy the space between dictionaries and structures: they hold very specific types of data (like a struct) but can be created on the fly (like dictionaries). They are commonly used to return multiple values from a function call.
Related Question Answers
What is force unwrapping in Swift?
Force unwrapping. Optionals represent data that may or may not be there, but sometimes you know for sure that a value isn't nil. In these cases, Swift lets you force unwrap the optional: convert it from an optional type to a non-optional type.What is unwrapping in Swift?
Swift Optionals and force unwrapping 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. The myOptionalString variable can contain a string value or nil.What is if let in Swift?
Unwrapping Optional Values in Swift 3.0 — Guard Let vs If Let? Many of us are familiar with Optional Binding and the “if let” syntax convention when unwrapping an optional value. The “if let” allows us to unwrap optional values safely only when there is a value, and if not, the code block will not run.What is exclamation mark in Swift?
The exclamation mark indicates that the name property of the Person class is defined as an implicitly unwrapped optional. Note that the print statement returns the value of name , not an optional.What is force unwrapping?
Force unwrap, or force-unwrap, or forced unwrapping, is the technique most of the previous post was actually about. It consist in adding a ! after an Optional value, to automatically unwrap it, without having to check whether it is nil or not.How do you declare an optional variable in Swift?
Optionals Overview When declaring variables in Swift, they are designated as non-optional by default. In other words, you have to assign a non-nil value to the variable. If you try to set a nil value to a non-optional, the compiler will say, “hey you can't set a nil value!”.What is optional chaining and optional binding?
Optional binding stores the thing you're binding in a variable. In this case, it's navigationController . On the other hand, optional chaining does not put the value on the left into a variable. it only says. I will check whether this value on the left of the question mark is nil.What is an optional in Java?
Optional is a container object used to contain not-null objects. This class has various utility methods to facilitate code to handle values as 'available' or 'not available' instead of checking null values. It is introduced in Java 8 and is similar to what Optional is in Guava.What is protocol in Swift?
A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality. The protocol can then be adopted by a class, structure, or enumeration to provide an actual implementation of those requirements.What is double question mark in Swift?
Double question mark is a nil-coalescing operator. In plain terms, it is just a shorthand for saying != nil . First it checks if the the return value is nil, if it is indeed nil, then the left value is presented, and if it is nil then the right value is presented.Do try catch Swift?
The try/catch syntax was added in Swift 2.0 to make exception handling clearer and safer. It's made up of three parts: do starts a block of code that might fail, catch is where execution gets transferred if any errors occur, and any function calls that might fail need to be called using try .What optional binding?
Use optional binding to find out whether an optional contains a value, and if so, to make that value available as a temporary constant or variable. An optional binding for the if statement is as follows − if let constantName = someOptional { statements }What is difference between if let and guard in Swift?
Generally that means it must call return or abort the program. guard is used to provide early return without requiring nesting of the rest of the function. if let nests its scope, and does not require anything special of it. It can return or not.Can I use optional chaining?
You can use optional chaining when attempting to call a method which may not exist. This can be helpful, for example, when using an API in which a method might be unavailable, either due to the age of the implementation or because of a feature which isn't available on the user's device.What is lazy in Swift?
Swift has a mechanism built right into the language that enables just-in-time calculation of expensive work, and it is called a lazy variable. These variables are created using a function you specify only when that variable is first requested. You can't make it lazy let because lazy properties must always be variables.What is forced unwrapping in Swift?
Like forced unwrapping, optional binding is a way of opening the box, but it does the job more cleverly and with less pollution than forced unwrapping. It allows to check the optional and extract its value into a constant or variable as part of a single action.What is nil coalescing operator in Swift?
What is the nil coalescing operator? Swift's nil coalescing operator helps you solve this problem by either unwrapping an optional if it has a value, or providing a default if the optional is empty.What is let in Swift?
Both let & var are used for declare variable in swift . Let: Let is used to declare constant variable that means immutable. The immutable variable can never be change if it is defined once. Example like let value = 42. Var : Var is used to declare variable which is mutable.What is guard in Swift?
The main use of guard statement is to transfer program control out of a scope on certain conditions. These statements are similar with if statements which executes statements based on certain condition (boolean value) but unlike if, the guard statements only run when certain conditions are not met. 
