How to Sum User-Generated Data

Question

Hu is I OP

Created Jan ’21

Replies 2

Boosts 0

Participants 3

Hello,

I'm trying to find the sum of a user-generated array by using the following code.

Code Block      let total = pointsReceived.reduce(0, +)

The above code doesn't work because, for some reason, it can't find 'pointsReceived' in scope.

I have this structure on the top of the page with the following data format:

Code Block struct Grade: Hashable, Identifiable {
  var id = UUID()
  var assessmentName: String!
  var pointsReceived: Double!
  var pointsPossible: Double!
}

I'm trying to add all the points received (there can be multiple rows of this data). How should I do that?

Thank you!

Answered by OOPer in 659241022

I'm trying to find the sum of a user-generated array by using the following code.

I have this structure on the top of the page with the following data format:

Where is the array? To apply reduce, the thing applied needs to be an Array. (Or at least a Sequence.)
In your shown code, there aren't any Arrays.

Assuming you have an Array of Grade,

Code Block var grades: [Grade] = [/*...*/]

you can write something like this:

Code Block let total = grades.reduce(0, {$0 + $1.pointsReceived})

By the way, why are you using Implicitly Unwrapped Optionals in your struct?

If you know the property can be nil, you should use normal Optionals:

Code Block struct Grade: Hashable, Identifiable {
    var id = UUID()
    var assessmentName: String?
    var pointsReceived: Double?
    var pointsPossible: Double?
}

(In this case, you need to update the code to reduce.)

Or else, if the property cannot be nil, you should better use non-Optional:

Code Block struct Grade: Hashable, Identifiable {
    var id = UUID()
    var assessmentName: String
    var pointsReceived: Double
    var pointsPossible: Double
}

Boost

Answer 1

Claude31 OP

Jan ’21

So, pointsReceived is inside a struct.

You probably have declare a var as:

Code Block var grade : Grade

And you have initialised with some value

You need to call:

Code Block  let total = grade.pointsReceived.reduce(0, +)

If that works, don't forget to close the thread by marking correct answer.
If not, please explain and show more code.

1

Answer 2

OOPer OP