Performing a sum with Swift

Question 1

I wrote the following in Swift to perform a sum:

let total:Double = session.courses.reduce(0) { $0 + $1.totalPrice() }

It's concise, it does the job but it does not seems very readable to me. Wouldn't a "classic"for loop be more explicit/readable/maintainable?

var total:Double = 0for dish in session.courses {    total += dish.totalPrice()}

Should closures always be the way to go in Swift?

Question 2

Both solutions are correct. Some advantages of the "functional" approachwithreduce():

Concise code.
Returns aconstant. It is clear to the reader thattotal is assigned to exactly once, and the compiler may use thisinformation for optimizing code.
The type annotation on the result value is not needed:
```
let total = session.courses.reduce(0) { $0 + $1.totalPrice() }
```
because that can be inferred from the compiler automatically.This will continue to compile without changes if the type oftotalPrice() is changed, e.g. fromDouble toFloat.

To increase legibility, you can use named closure parameters insteadof the$n shortcuts:

let total = session.courses.reduce(0) { (partialSum, dish) in    partialSum + dish.totalPrice()}

Question 3

+1 for legibility! I find the$n shortcuts incredibly hard to read, and they offer no information on what the values represent.

Question 4

Another alternatives:

let sum = session.courses.map({$0.totalPrice()}).reduce(0, +)

Another note, I think it's more elegant to implementtotalPrice as computed variable instead of function.

Another way is to useforEach :

var sum = 0session.courses.forEach {sum+=$0.totalPrice()}

as @Martin R mentioned the functional approach has some advantages especially that the result is constant.

Martin R 24.2k2 gold badges38 silver badges96 bronze badges · Answer 1 · 2018-01-12 12:09:40Z