How to group array of objects by date in swift?

问题:

Need to group according to date. Response coming is in sorted format. Need to apply a filter on date to group. Response coming from backend:

[
    {
    "date": "date1"
    }, 
    {
    "date": "date1"
    },
    {
    "date": "date1"
    },
    {
    "date": "date2"
    },
    {
    "date": "date2"
    },
    {
    "date": "date3"
    }
]

Required:

[
    [
        "date": "2017-05-30T12:40:39.000Z",
        "message": [
            {
                "date_time": 2017-05-30T12: 40: 39.000Z
            }
        ]
    ],
    [
        "date": "2017-05-31T05:43:17.000Z",
        "message": [
            {
                "date_time": 2017-05-31T05: 43: 17.000Z
            },
            {
                "date_time": 2017-05-31T05: 44: 15.000Z
            },
            {
                "date_time": 2017-05-31T05: 44: 38.000Z
            }
        ]
    ]
]

I have checked multiple answers but wasn't able to find a good solution.

回答1:

This is my solution to group by date(just day, month and year):

let groupDic = Dictionary(grouping: arr) { (pendingCamera) -> DateComponents in

    let date = Calendar.current.dateComponents([.day, .year, .month], from: (pendingCamera.date)!)

    return date
}

回答2:

You can use flatMap and filter like this to group your array to dictionary.

let datesArray = yourArray.flatMap { $0["date"] as? String } // return array of date
var dic = [String:[[String:Any]]]() // Your required result
datesArray.forEach {
    let dateKey = $0
    let filterArray = yourArray.filter { $0["date"] as? String == dateKey }
    dic[$0] = filterArray
}
print(dic)

Note: Make sure one thing that dictionary don't have any order so order of printing of date might changed.

回答3:

Thank you ElegyD. This is worked for me.

extension Sequence {
    func groupSort(ascending: Bool = true, byDate dateKey: (Iterator.Element) -> Date) -> [[Iterator.Element]] {
        var categories: [[Iterator.Element]] = []
        for element in self {
            let key = dateKey(element)
            guard let dayIndex = categories.index(where: { $0.contains(where: { Calendar.current.isDate(dateKey($0), inSameDayAs: key) }) }) else {
                guard let nextIndex = categories.index(where: { $0.contains(where: { dateKey($0).compare(key) == (ascending ? .orderedDescending : .orderedAscending) }) }) else {
                    categories.append([element])
                    continue
                }
                categories.insert([element], at: nextIndex)
                continue
            }

            guard let nextIndex = categories[dayIndex].index(where: { dateKey($0).compare(key) == (ascending ? .orderedDescending : .orderedAscending) }) else {
                categories[dayIndex].append(element)
                continue
            }
            categories[dayIndex].insert(element, at: nextIndex)
        }
        return categories
    }
}

Usage:

class Model {
    let date: Date!
    let anotherProperty: String!

    init(date: Date, _ anotherProperty: String) {
        self.date = date
        self.anotherProperty = anotherProperty
    }
}

let modelArray = [
    Model(date: Date(), anotherProperty: "Original Date"),
    Model(date: Date().addingTimeInterval(86400), anotherProperty: "+1 day"),
    Model(date: Date().addingTimeInterval(172800), anotherProperty: "+2 days"),
    Model(date: Date().addingTimeInterval(86401), anotherProperty: "+1 day & +1 second"),
    Model(date: Date().addingTimeInterval(172801), anotherProperty: "+2 days & +1 second"),
    Model(date: Date().addingTimeInterval(86400), anotherProperty: "+1 day"),
    Model(date: Date().addingTimeInterval(172800), anotherProperty: "+2 days")
]

let groupSorted = modelArray.groupSort(byDate: { $0.date })
print(groupSorted) // [["Original Date"], ["+1 day", "+1 day", "+1 day & +1 second"], ["+2 days", "+2 days", "+2 days & +1 second"]]

let groupSortedDesc = modelArray.groupSort(ascending: false, byDate: { $0.date })
print(groupSortedDesc) // [["+2 days & +1 second", "+2 days", "+2 days"], ["+1 day & +1 second", "+1 day", "+1 day"], ["Original Date"]]