Sorting array of dictionaries of strings in Swift

Question

I'm trying to sort an array of dictionaries in Swift. My structure is like this:

[
    [
        "DateTime": "8/16/16, 4:00 PM",
        "Owner": "Teacher1",
        "Subject": "AP Euro",
        "Address": "Mr. Hughes\' Room",
        "Type": "Final",
        "Timestamp": "2016081616009498",
        "Location": "On Campus",
        "Duration": "50 min",
        "Members": "ownerKey,1,107434,109431"
    ],
    [
        "DateTime": "7/29/16, 6:35 AM",
        "Owner": "109431",
        "Subject": "Algebra 2 Acc",
        "Address": "Library",
        "Type": "Quiz",
        "Timestamp": "2016072906356642",
        "Location": "On Campus",
        "Duration": "5 min",
        "Members": "ownerKey"
    ]
]

I'm trying to sort the array by each "Timestamp" value in each dictionary. How can I do this?

My current code (not working) is:

self.todayArray.sortInPlace {item1,item2 in

    let date1 = Int("\(item1["Timestamp"])")
    let date2 = Int("\(item2["Timestamp"])")

    return date1 > date2
}

Your timestamp might be too large for a 32bit integer. Use return Double(item1["Timestamp"]!) < Double(item2["Timestamp"]!) instead. — J.Wang
– J.Wang, Commented Jul 29, 2016 at 6:19

David Berry · Accepted Answer · 2016-07-29 17:44:04Z

5

N/M all the stuff below, it's to sort by the DateTime field, you're trying to sort on the Timestamp field which is already lexicographically sorted, so just use:

foo.sortInPlace { $0["Timestamp"] < $1["Timestamp"] }

Since timestamp is an string-encoded date, you'll need to convert it to something more useful first, using an NSDateFormatter is the easiest way:

There's a lot of ! in here that you should do something more appropriate with, but this gives you the basic idea:

let foo = [
    [
        "DateTime": "8/16/16, 4:00 PM",
        "Owner": "Teacher1",
        "Subject": "AP Euro",
        "Address": "Mr. Hughes\' Room",
        "Type": "Final",
        "Timestamp": "2016081616009498",
        "Location": "On Campus",
        "Duration": "50 min",
        "Members": "ownerKey,1,107434,109431"
    ],
    [
        "DateTime": "7/29/16, 6:35 AM",
        "Owner": "109431",
        "Subject": "Algebra 2 Acc",
        "Address": "Library",
        "Type": "Quiz",
        "Timestamp": "2016072906356642",
        "Location": "On Campus",
        "Duration": "5 min",
        "Members": "ownerKey"
    ]
]

let formatter = NSDateFormatter()
formatter.dateFormat = "M/dd/yy, h:mm a"

let sorted = foo.sort {
    formatter.dateFromString($0["DateTime"]!)!.compare(formatter.dateFromString($1["DateTime"]!)!) != .OrderedDescending
}
print("\(sorted)")

edited Jul 29, 2016 at 17:44

answered Jul 29, 2016 at 6:17

David Berry

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2 Comments

Albert Ghar Over a year ago

Should foo.sort { $0["Timestamp"] < $1["Timestamp"] } be foo.sortInPlace { $0["Timestamp"] < $1["Timestamp"] }?

David Berry Over a year ago

Depends on what you want. To mimic your original code, yes, sortInPlace is appropriate. I just try to avoid using it most of the time.

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