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iOS Swift Basics (retired) Types Numbers

I think the question for task #2 is incorrect, it is asking for a constant when it should be asking for a variable. Yes?

The request is to create a constant - but it is for price = 9.99 which should be a var

let title = "A Dance with Dragons"
var price = 9.99 // double 

2 Answers

Stone Preston
Stone Preston
42,016 Points

task 2 states: Next create a constant called price and assign it the value 9.99.

you define constants using the let keyword

let someConstant = someValue

so you would use:

let title = "A Dance with Dragons"
let price = 9.99

Constant values cannot change after they are set. using a constant in this instance is correct if we dont want the price to ever change. In this case the we want the price of A Dance With Dragons to always be 9.99, so it makes sense to use a constant

It does not matter that price is a double. any data type can be a constant and any data type can be a var. The difference is that the values of vars can change, and the value of constants cannot.

for more information on constants and variables see the Swift eBook which explains the main difference between constants and variables:

Constants and variables associate a name (such as maximumNumberOfLoginAttempts or welcomeMessage) with a value of a particular type (such as the number 10 or the string "Hello"). The value of a constant cannot be changed once it is set, whereas a variable can be set to a different value in the future.

thank you! when I was checking the work, it stated it should be a "double" but //double wasn't letting y work get approved - I tried it in xCode and it seems fine - prob user error :)

Stone Preston
Stone Preston
42,016 Points

ah. well swift infers its type as double. you could have explicitly declared the type as double if you wanted:

let price: Double = 9.99

note that price is still declared as a constant, it just has an explicit type (as opposed to an inferred type)