Trailing closure syntax in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is trailing closure syntax in Swift?

Trailing closure syntax lets you write a closure outside the parentheses of a function call when the closure is the last argument.

beginner

How do you write a trailing closure for a function with one closure parameter?

You call the function without passing the closure inside parentheses. Instead, you write the closure after the function call parentheses.

beginner

Example: Convert this call to use trailing closure syntax:<br>array.map({ number in number * 2 })

Using trailing closure syntax:<br>array.map { number in number * 2 }

intermediate

Can you use trailing closure syntax if the closure is not the last argument?

No. Trailing closure syntax only works if the closure is the last argument in the function call.

beginner

Why is trailing closure syntax useful?

It makes code cleaner and easier to read, especially when the closure is long or multi-line.

What does trailing closure syntax allow you to do in Swift?

A Write the last closure argument outside the parentheses

B Write all closures inside the parentheses

C Use closures only with no arguments

D Avoid using closures entirely

Trailing closure syntax lets you write the last closure argument outside the parentheses for cleaner code.

Which of these is a correct use of trailing closure syntax?

A functionName(5, { /* closure code */ })

B functionName({ /* closure code */ })

C functionName({ /* closure code */ }, 5)

D functionName() { /* closure code */ }

Trailing closure syntax is used when the closure is the last argument and written outside the parentheses.

Can you use trailing closure syntax if the function has multiple parameters and the closure is not last?

A No, only if closure is last

B Yes, always

C Yes, but only for one parameter functions

D No, closures cannot be trailing

Trailing closure syntax only works if the closure is the last argument in the function call.

What is the benefit of using trailing closure syntax?

A Makes code longer

B Makes code cleaner and easier to read

C Removes the need for closures

D Makes code harder to read

Trailing closure syntax improves readability by making closure code clearer and less cluttered.

Which Swift function call uses trailing closure syntax correctly?

A numbers.filter({ $0 > 5 }, true)

B numbers.filter({ $0 > 5 })

C numbers.filter { $0 > 5 }

D numbers.filter(true, { $0 > 5 })

The closure is the last argument and written outside parentheses, which is correct trailing closure syntax.

Explain what trailing closure syntax is and when you can use it in Swift.

Think about how closures are passed to functions and where you place them.

Describe the benefits of using trailing closure syntax in your Swift code.

Consider how code looks with and without trailing closures.