Why let and var distinction matters in Swift - Quick Recap

Recall & Review

beginner

What is the difference between let and var in Swift?

let declares a constant, which means its value cannot change after being set. var declares a variable, which means its value can change over time.

beginner

Why should you prefer let over var when possible?

Using let helps prevent accidental changes to data, making your code safer and easier to understand.

beginner

What happens if you try to change a value declared with let?

Swift will give a compile-time error because constants cannot be changed once set.

intermediate

How does using let improve code readability?

It signals to readers that the value will not change, so they can trust it stays the same throughout the code.

intermediate

Can you change properties of a class instance declared with <code>let</code>?

Yes, if the properties are variables (var) inside the class, you can change them even if the instance is declared with let. But you cannot assign a new instance to that constant.

What keyword do you use in Swift to declare a value that cannot change?

A let

B var

C const

D static

let declares a constant in Swift, which means the value cannot be changed.

What happens if you try to assign a new value to a let constant?

A The program runs normally

B The program crashes at runtime

C The value changes silently

D A compile-time error occurs

Swift prevents changing constants by giving a compile-time error.

Why is it safer to use let instead of var when possible?

A Because <code>let</code> uses less memory

B Because <code>let</code> prevents accidental changes

C Because <code>var</code> is slower

D Because <code>var</code> is deprecated

let makes your code safer by preventing accidental value changes.

If you declare a class instance with let, can you change its variable properties?

A No, nothing can change

B Only if the class is a struct

C Yes, variable properties can change

D Only if you use <code>var</code> inside the class

The instance reference is constant, but its variable properties can still change.

Which keyword should you use to declare a variable that can change?

A var

B const

C let

D final

var declares a variable whose value can change.

Explain why distinguishing between let and var is important in Swift programming.

Think about how changing or not changing values affects your program.

Describe a situation where using let instead of var can help avoid errors.

Consider a value like a fixed tax rate or a username that should not change.