Test for playgrounds

import Cocoa

let a = 5

print(a > 5 ? 1 : (a < 5 ? 9 : 2))

works as expected

now in swiftui to solve Iexpense challenge

//
//  ContentView.swift
//  Project7
//
//  Created by Paul Hudson on 17/02/2020.
//  Copyright © 2020 Paul Hudson. All rights reserved.
//

import SwiftUI

struct ExpenseItem: Identifiable, Codable {
    let id = UUID()
    let name: String
    let type: String
    let amount: Int
}

class Expenses: ObservableObject {
    @Published var items: [ExpenseItem] {
        didSet {
            let encoder = JSONEncoder()
            if let encoded = try? encoder.encode(items) {
                UserDefaults.standard.set(encoded, forKey: "Items")
            }
        }
    }

    init() {
        if let items = UserDefaults.standard.data(forKey: "Items") {
            let decoder = JSONDecoder()
            if let decoded = try? decoder.decode([ExpenseItem].self, from: items) {
                self.items = decoded
                return
            }
        }

        self.items = []
    }
}

struct ContentView: View {
    @ObservedObject var expenses = Expenses()
    @State private var showingAddExpense = false

    var body: some View {
        NavigationView {
            List {
                ForEach(expenses.items) { item in
                    HStack {
                        VStack(alignment: .leading) {
                            Text(item.name)
                                .font(.headline)
                            Text(item.type)
                        }

                        Spacer()
                        Text("$\(item.amount)")
                    }
                    .foregroundColor(item.amount < 10 ? .red : (item.amount < 100 ? .blue : .black)) // same chaining here but compiler cant compile throughs error that it takes too much time to compile.

                }
                .onDelete(perform: removeItems)
            }
            .navigationBarTitle("iExpense")
            .navigationBarItems(leading: EditButton(),trailing:
                Button(action: {
                    self.showingAddExpense = true
                }) {
                    Image(systemName: "plus")
                }
            )
            .sheet(isPresented: $showingAddExpense) {
                AddView(expenses: self.expenses)
            }
        }
    }

    func removeItems(at offsets: IndexSet) {
        expenses.items.remove(atOffsets: offsets)
    }

    func styling (for: Int)
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

error: The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions

if I will reduce conditions of ternery to 1 if else block i.e. condition ? statement : statement . then it will compile and run as it should

Solved with adding new modifier but still cant understand why ternery doesnt want to work.

struct fontStyling: ViewModifier{
    var amount:Int

    func body(content: Content) -> some View {

        var color = Color.black

        if amount < 10 {
            color = Color.blue
        }

        else if amount < 100 {
            color = Color.green
        }

        else if amount < 1000 {
            color  = Color.yellow
        }

        return content
        .foregroundColor(color)
    }
}

I was going to suggest replacing .red with Color.red, etc. Maybe trying to figure out the data type there has caused the delay.

tried with Color.red didnt help same error.