Swift - display a sorted array with keys

Question

I am want to display the three highest grades along with the names

My code:

let gradesofStudent = [
    "Elias Brown": 80,
    "Baris Yan": 99,
    "Christian Najm": 70,
    "Sam  Chakra": 90,
    "Alain Elliot": 55,
    "Georges Obama": 77,
]
   var y = " "
   var name = " " 
func mainFunction(stDictionary: Dictionary<String, Int>) -> ArraySlice<String>{

        var emptyDic: [String: String] = [:]


   for (keys, value) in gradesofStudent {

    if value > 0 && value <= 59 {y = "F"} 
else if value >= 60 && value <= 69 {y = "D"}
else if value >= 70 && value <= 79 {y = "C"}
else if value >= 80 && value <= 89 {y = "B"}
else  {y = "A"}
emptyDic[keys] = y
    }

var arrayGrades = (Array(emptyDic).sorted{$0.1 < $1.1}).map{(k,v) in return(k:v)}
var firstThree = arrayGrades[0..<3]

return(k: firstThree)
}
let v = mainFunction(stDictionary:gradesofStudent)
print (v)

I am getting the following output:

["A", "A", "B"]

What I want to get is something like [ "Baris Yan":"A", "Sam Chakra":"A", "Elias Brown":"B"]

Since i can't seem to sort the dictionary directly, I can't figure how to display the names.

You can make your life so much easier if you would use a struct Student with var name : String, var grade : Int members, computed property var letterRepresentation : String { ...} and an array of instances. Btw: A dictionary is unordered by definition. — vadian
– vadian, Commented Jun 17, 2017 at 20:55

vadian · Accepted Answer · 2017-06-17 21:19:53Z

1

My two cents (according to the comment)

struct Student {
    let name : String
    let grade : Int

    var letterRepresentation : String {
        switch grade {
        case 0..<60 : return "F"
        case 60..<70 : return "D"
        case 70..<80 : return "C"
        case 80..<90 : return "B"
        default : return "A"
        }
    }
}

let gradesofStudent = [Student(name: "Elias Brown", grade: 80),
                       Student(name: "Baris Yan", grade: 99),
                       Student(name: "Christian Najm", grade: 70),
                       Student(name: "Sam  Chakra", grade: 90),
                       Student(name: "Alain Elliot", grade: 55),
                       Student(name: "Georges Obama", grade: 77)]

let threeHighestGrades = gradesofStudent.sorted(by: {$0.grade > $1.grade}).prefix(3)

print(threeHighestGrades.map({"\($0.name) - \($0.letterRepresentation)"}))
// ["Baris Yan - A", "Sam  Chakra - A", "Elias Brown - B"]

Is there no letter E ?

edited Jun 17, 2017 at 21:19

answered Jun 17, 2017 at 21:15

vadian

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2 Comments

Paulo Mattos Over a year ago

Silly typo: your switch will give A to grades 69 and 79.

vadian Over a year ago

Oops. Thanks a lot @PauloMattos

Arthi · Accepted Answer · 2017-06-17 21:21:33Z

The below code snippet would give you the exact result you need:

let gradesofStudent = [ "Elias Brown": 80, "Baris Yan": 99, "Christian Najm": 70, "Sam Chakra": 90, "Alain Elliot": 55, "Georges Obama": 77, ]

var y = " "

var name = " "

func mainFunction(stDictionary: Dictionary)->ArraySlice<[String : String]> {

var emptyDic: [String: String] = [:]


for (keys, value) in gradesofStudent {

    if value > 0 && value <= 59 {y = "F"}
    else if value >= 60 && value <= 69 {y = "D"}
    else if value >= 70 && value <= 79 {y = "C"}
    else if value >= 80 && value <= 89 {y = "B"}
    else  {y = "A"}
    emptyDic[keys] = y
}

var arrayGrades = emptyDic.sorted{$0.1 < $1.1}.map{(k,v) in return[k:v]}
var firstThree = arrayGrades[0..<3]
return(firstThree)

}

let v = mainFunction(stDictionary:gradesofStudent) print (v)

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