Question: What Is Swift Optional?

What is the meaning of in Swift?

Means you can assign default value nil or any other value if something[“something”] is nil or optional) let val = (something[“something”] as.

String) != nil .

( something[“something”] as!.

Why do we use optionals 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.

What is if let in Swift?

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. Simply put, its focus is on the “true” condition when a value exists.

How do I check if a swift Keyal is empty?

You can use an if statement to find out whether an optional contains a value. If an optional does have a value, it evaluates to true; if it has no value at all, it evaluates to false. and if you are using the xyz in if statement. Than you can unwrap xyz in if statement in constant variable .

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.

How do I force unwrap in Swift?

Even though Swift isn’t sure the conversion will work, you can see the code is safe so you can force unwrap the result by writing ! after Int(str) , like this: let num = Int(str)! Swift will immediately unwrap the optional and make num a regular Int rather than an Int? .

What are closures in Swift?

Closures are self-contained blocks of functionality that can be passed around and used in your code. Closures in Swift are similar to blocks in C and Objective-C and to lambdas in other programming languages. … Nested functions are closures that have a name and can capture values from their enclosing function.

How Optional is implemented in Swift?

Optionals are implemented as enum type in Swift. Optionals are implemented as shown below. To find this, CMD-Click on a declaration like var x: Optional . var x: Int? is just syntactic sugar for that.

How do I stop optional in Swift?

14 Answers. Actually when you define any variable as a optional then you need to unwrap that optional value. To fix this problem either you have to declare variable as non option or put !( exclamation) mark behind the variable to unwrap the option value.

What’s the difference between optional none .none for short and nil?

Answer : There is no difference. Optional. None (. None for short) is the correct way of initializing an optional variable lacking a value, whereas nil is just syntactic sugar for .

Can any be nil Swift?

This feels like it doesn’t make much sense. bar is not optional in this case, and thus should never be nil, but it can be nil. Because bar is not optional, you cannot utilize any of the unwrapping methods Swift provides (guard, if let, ??, !)

What is delegate in Swift?

Delegation is used for everything from handling table view events using UITableViewDelegate , to modifying cache behavior using NSCacheDelegate . The core purpose of the delegate pattern is to allow an object to communicate back to its owner in a decoupled way.

How does Swift handle optional value?

To use the wrapped value inside an optional, you have to unwrap it. The simplest way to unwrap an optional is to add a ! after the optional name. This is called “force unwrapping”. It returns the value inside the optional (as the original type) but if the optional is nil , it causes a runtime crash.

Can let be optional in Swift?

In Swift, optionals are nil or have a value. Before you can use an optional, you’ll need to unwrap it. Optionals are a powerful feature of the Swift programming language, because they make your code safer and more productive. And as an iOS developer, it’s important you know how to use optionals.

What is unwrapping in Swift?

Unwrapping an optional means that you are now casting that type as non-optional. This will generate a new type and assign the value that resided within that optional to the new non-optional type. This way you can perform operations on that variable as it has been guaranteed by the compiler to have a solid value.

What is nil in Swift?

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 .

What is difference between if 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.

What is difference between guard and if let?

guard let will unwrap an optional for you, but if it finds nil inside it expects you to exit the function, loop, or condition you used it in. However, the major difference between if let and guard let is that your unwrapped optional remains usable after the guard code.

How do I make an array optional in Swift?

swift-optional-arrays var unwrappedArray1: String[] = optionalArray! var unwrappedArray2: String[] = optionalArray! // unwrappedArray1 === optionalArray! // Error: Operand of postfix ‘! ‘ should have optional type; type of ‘String[]?

What is a bundle in iOS?

A bundle is a directory in the file system that groups executable code and related resources such as images and sounds together in one place. In iOS and OS X, applications, frameworks, plug-ins, and other types of software are bundles.

What is Guard Swift?

Here’s what the official Swift documentation says about guard : A guard statement is used to transfer program control out of a scope if one or more conditions aren’t met. What it means is that you use guard to exit a function (“transfer control out of scope”) when a condition isn’t met.