What is optionals in Swift?

An optional in Swift is basically a constant or variable that can hold a value OR no value. The value can or cannot be nil. It is denoted by appending a “?” after the type declaration. The tweet string is now declared as an optional.

How do I unwrap optionals in Swift?

You can force unwrap an optional by adding an exclamation mark after the optional constant or variable, like this: print(email!) Now, consider the following two scenarios: Instead of having a value, email is nil .

How do you write comments in Swift?

Use comments to include nonexecutable text in your code, as a note or reminder to yourself. Comments are ignored by the Swift compiler when your code is compiled. Comments in Swift are very similar to comments in C. Single-line comments begin with two forward-slashes ( // ): // This is a comment.

How do you declare a variable in Swift?

You can declare a variable with the var keyword, and you don’t need to explicitly declare the variable’s type. However, remember that every variable—and constant—has a type in Swift. If Swift can’t infer the type, then it complains. Every variable has a type, and that type cannot be changed.

What is the difference between VAR and let in Swift?

What is the difference between them ? Both let and var are for creating variables in Swift. let helps you create immutable variables (constants) while on the other hand var creates mutable variables.

What is unwrapped 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 Mark in Swift?

MARK simply adds a visual MARK in the jump bar like this: ex // MARK: Core Data Stack. https://stackoverflow.com/questions/35963128/swift-understanding-mark/35963224#35963224.

How do I view Apple documents?

In many apps, your Mac can read aloud documents, webpages, messages, and more. In an app on your Mac, do any of the following: Hear an entire document: Choose Edit > Speech > Start Speaking. Hear part of a document: In a document, select the text you want to hear, then choose Edit > Speech > Start Speaking.

Is Swift or Python better?

The performance of the swift and python vary, swift tends to be swift and is faster than python. If you are developing applications that will have to work on Apple OS, you can choose swift. In case if you want to develop your artificial intelligence or build the backend or create a prototype you can choose python.

Which language is closest to Swift?

Rust and Swift are probably the most conceptually similar, and target fairly similar uses. Syntactically, it borrows from all over the place though; ObjC, Python, Groovy, Ruby, etc…

Is Let better than VAR?

If you are using ES6+ syntax then no, not really. The let and const declarations provide better scope management than the traditional var. Plus the var keyword may confuse programmers coming from other languages like VB or Java that use var to declare variables, but with different rules.

When do you use optional type in Swift?

A type that represents either a wrapped value or nil, the absence of a value. You use the Optional type whenever you use optional values, even if you never type the word Optional. Swift’s type system usually shows the wrapped type’s name with a trailing question mark (?) instead of showing the full type name.

What happens if optional is nil in Swift?

If the optional contains a value, the property, method, or subscript call succeeds; if the optional is nil, the property, method, or subscript call returns nil. Multiple queries can be chained together, and the entire chain fails gracefully if any link in the chain is nil.

Why do I need to unwrap optionals in Swift?

The value is wrapped in Optional ( ” ··· “), instead of just printing the value of the string literal. That’s because you need to unwrap optionals to access their values. More on unwrapping later. You can’t assign nil to a variable or constant that’s not an optional.

What is the name of the unwrapped variable in Swift?

Note: You can give your conditionally unwrapped constant the same name as the optional variable you are unwrapping. Conditionally unwrapping optionals is the cleanest way to access an optional’s value because if it contains a nil value then everything within the if let block will not execute.