Array iteration and enumerated in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the enumerated() method do when used on an array in Swift?

The enumerated() method returns a sequence of pairs, where each pair contains an index and the corresponding element from the array. This helps to access both the position and value during iteration.

beginner

How do you write a simple for-in loop to iterate over all elements in a Swift array named fruits?

You write: <br>for fruit in fruits {<br> print(fruit)<br>}<br>This prints each fruit in the array one by one.

intermediate

Why might you want to use enumerated() instead of a simple for-in loop?

Using enumerated() lets you know the index of each element while looping. This is useful when you need to know the position of the item, like numbering a list or updating elements by index.

intermediate

What is the type of the value returned by enumerated() on an array?

It returns a sequence of tuples where each tuple has two parts: an Int index and the element of the array's type. For example, (Int, String) if the array holds strings.

beginner

Write a Swift code snippet that prints the index and value of each element in an array colors using enumerated().

let colors = ["Red", "Green", "Blue"]
for (index, color) in colors.enumerated() {
    print("\(index): \(color)")
}
This prints:<br>0: Red<br>1: Green<br>2: Blue

What does the enumerated() method return when called on an array?

A Only the elements of the array

B A sequence of (index, element) pairs

C Only the indices of the array

D A reversed array

enumerated() returns pairs of index and element, allowing access to both during iteration.

How do you access the index and value inside a for-in loop using enumerated()?

A for (index, value) in array.enumerated()

B for index in array.enumerated()

C for value in array.enumerated()

D for array in (index, value)

You use tuple unpacking: for (index, value) in array.enumerated().

Which of these is a correct way to iterate over an array numbers to print each element?

A for number in numbers { print(number) }

B numbers.forEach(print)

C All of the above

D for (index, number) in numbers.enumerated() { print(number) }

All listed methods correctly iterate and print elements of the array.

What type is the index provided by enumerated()?

A Int

B String

C Double

D Bool

The index is always an Int representing the position in the array.

If you want to print the position starting from 1 instead of 0 using enumerated(), what should you do?

A Subtract 1 from the index

B Use <code>enumerated(startingAt: 1)</code>

C You cannot change the starting index

D Add 1 to the index inside the loop

You add 1 to the index manually inside the loop to start counting from 1.

Explain how to use enumerated() to loop through an array and access both the index and the element.

Think about how you get both position and value in one loop.

Describe the difference between a simple for-in loop over an array and using enumerated() in Swift.

One gives you just the items, the other gives you items with their positions.