gistfile1.txt

import UIKit

var str = """
{
"report":[
{
"enrollment": "rit2011001",
"name": "Julia",
"subject":[
{
"code": "NLP",
"grade": "A"
},
{
"code": "DSA",
"grade": "A"
}
]
},
{
"enrollment": "rit2011020",
"name": "Samantha",
"subject":[
{
"code": "COM",
"grade": "B"
},
{
"code": "OOM",
"grade": "A"
},
{
"code": "DSA",
"grade": "A"
}
]
}
]
}
"""

struct ReportData: Decodable {
    let report: [Report]
}


struct Report: Decodable {
    let enrollment: String
    let name: String
    let subject: [Subject]
}

struct Subject: Decodable {
    let code: String
    let grade: String
}

struct Tuple {
    let name: String
    let enrollment: String
    let code: String
    let grade: String
}

func decodeReports() {
    let jsonDecoder = JSONDecoder()
    guard let data = str.data(using: .utf8),
        let reportsData = try? jsonDecoder.decode(ReportData.self, from: data) else {
            fatalError("Error decoding json")
    }
    let reports = reportsData.report
    let tuples = reports.flatMap {  report in
        return report.subject.map {
            return Tuple(name: report.name, enrollment: report.enrollment, code: $0.code, grade: $0.grade)}
    }
    let ordered = tuples.sorted {
        guard $0.code == $1.code else { return $0.code < $1.code }
        guard $0.grade == $1.grade else { return $0.grade > $1.grade }
        guard $0.enrollment == $1.enrollment else { return $0.enrollment < $1.enrollment }
        return $0.name > $1.name
    }
    for t in ordered {
        print("\(t.code)    \(t.grade)    \(t.enrollment)    \(t.name)")
    }
}

decodeReports()