SOLVED: grouped table by object's date property

@gonzalocastro

Oct '20

I have Person class,

class Person: Identifiable {
    var name: String
    var DOB: Date

    init(name: String, DOB: Date) {
        self.name = name
        self.DOB = DOB
    }
}

I have a PersonModelView which has an array of Persons.

var persons: [Person] = []

My SwiftUI View has a PersonModelView.

How would I go about displaying the persons in a List grouped by months based on each Person's upcoming birthdays?

The List would would looks this:

This month:
    Jane
    Paul
    Kevin
November, 2020:
    Sally
    Phoebe
    Cecil
December, 2020:
    Harold
    Ben
January, 2021:
    Cathy

Thanks, Gonzalo

@delawaremathguy

Oct '20

hi,

if you just want the persons collected by month, from 1 through 12, use a dictionary and then rearrange its values (each value has type [Person]) by key into an array (which will have type [[Person]]. For example:

func personsByMonth() -> [[Person]] {
  guard !persons.isEmpty else { return [] }
  let dictionaryByMonth = Dictionary(grouping: persons, by: { $0.month })
  let months = Array(1...12) // rotate this array if you want to go from October to September
  return months.compactMap({ dictionaryByMonth[$0] })
}

the code above assumes that Person has a computed property month, an integer from 1 to 12, which you can compute from the DOB using its DateComponents. the compactMap operator is needed because some keys will not exist in the dictionary; only non-empty arrays of people by month will be returned as a result.

now you can display them in a grouped list:

List {
  ForEach(personsByMonth(), id: \.self) { personsInMonth in
    Section(header: Text(headerText(for: personsInMonth))) {
      ForEach(personsInMonth) { person in
        Text(person.name)
      } // end of ForEach
    } // end of Section
  } // end of ForEach
} // end of List

to figure out an appropriate headerText(for: personsInMonth) function, just recognize that all persons in personsInMonth share the same birthday month; so just read the month of any one of them, e.g., personsInMonth[0].month.

hope that helps,

DMG

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