Swift gives us an alternative to if let called guard let , which also unwraps optionals if they contain a value, but works slightly differently: guard let is designed to exit the current function, loop, or condition if the check fails, so any values you unwrap using it will stay around after the check.
What is the difference between guard let and if let?
With guard let you are creating a new variable that will exist outside the else statement. With if let you aren’t creating any new variable—after the else statement, you only enter the code block if the optional is non-nil. The newly created variable exists only inside the code block not after!
What is guard 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. … Using guard let lets you deal with problems at the start of your functions, then exit immediately.
What is difference between if let and guard in Swift?
In if let , the defined let variables are available within the scope of that if condition but not in else condition or even below that. In guard let , the defined let variables are not available in the else condition but after that, it’s available throughout till the function ends or anything.
When to use if let and guard?
So, use if let if you just want to unwrap some optionals, but prefer guard let if you’re specifically checking that conditions are correct before continuing.
When should I use Swift guard?
Swift guard is defined as a statement that is used to transfer program control out of a scope if one or more conditions aren’t met. What it means is that it is essentially a redirection or early exit of a statement or function to prevent crashing and incorrect data.
What is guard in Swiftui?
Swift’s guard keyword lets us check an optional exists and exit the current scope if it doesn’t, which makes it perfect for early returns in methods.
Why optionals are useful 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 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 I use defer in Swift?
Swift’s defer keyword lets us set up some work to be performed when the current scope exits. For example, you might want to make sure that some temporary resources are cleaned up once a method exits, and defer will make sure that happens no matter how that exit happens.
What is a guard function?
The guard provides an early exit from a subroutine, and is a commonly used deviation from structured programming, removing one level of nesting and resulting in flatter code: replacing if guard { … } with if not guard: return; … . …
What should be the type of the value of guard expression?
6. What should be the type of the value of guard expression? Explanation: The type of result of guard expression should be BOOLEAN which may take only two values either TRUE or FALSE. The statements under guarded block are executed only when the result of guard expression is TRUE.
Are closures value or reference types?
In Swift, structs, enums and tuples are all value types, while classes and closures are reference types. In a nutshell, a value type contains data and a reference type contains the location in memory where data lives.