How can I combine the date into a dictionary? - ios

Question

I'm having trouble with Dictionary.
For example,
My current data
["date": "2018-01-01", "name": "New Year"], ["date": "2018-01-31", "name": "Public holiday"],["date": "2018-02-14", "name": "Valentine's Day"], ["date": "2018-02-28", "name": "Public Holiday"]
How can I transform to
["month": ["January": ["date": "2018-01-01", "name": "New Year"], ["date": "2018-01-31", "name": "Public holiday"]],["February": ["date": "2018-02-14", "name": "Valentine's Day"], ["date": "2018-02-28", "name": "Public Holiday"]]]

Answer 1

You can use DateFormatter to read the String format dates (yyyy-MM-dd) into Date instances, and subsequently re-use the formatter to extract the full month names (MMMM) from the dates as your String key.
Combine this with reduce(into:) to process the data array:
let data = [
["date": "2018-01-01", "name": "New Year"],
["date": "2018-01-31", "name": "Public holiday"],
["date": "2018-02-14", "name": "Valentine's Day"],
["date": "2018-02-28", "name": "Public Holiday"]
]
let monthCategorizedData = data
.reduce(into: (result: [String: [[String: String]]](),
formatter: DateFormatter(),
calendar: Calendar(identifier: .gregorian))) {(args, data) in
var month = "Unknown"
args.formatter.dateFormat = "yyyy-MM-dd" // format: read date from string
if let date = data["date"].flatMap({ args.formatter.date(from: $0)}) {
args.formatter.dateFormat = "MMMM" // format: read month (as string) from date
month = args.formatter.string(from: date)
}
args.result[month] = args.result[month, default: []] + [data]
}.result
print(monthCategorizedData)
/* ["January": [["date": "2018-01-01", "name": "New Year"],
["date": "2018-01-31", "name": "Public holiday"]],
"February": [["date": "2018-02-14", "name": "Valentine\'s Day"],
["date": "2018-02-28", "name": "Public Holiday"]]] */
In case of data with invalid dates (String form to Date fails, or "date" key does not exist in the data), the above will categorize them into the key Unknown. If you'd rather just discard such data (as such a failure should be unexpected), you can modify the above to:
let monthCategorizedData = data
.reduce(into: (result: [String: [[String: String]]](),
formatter: DateFormatter(),
calendar: Calendar(identifier: .gregorian))) {(args, data) in
args.formatter.dateFormat = "yyyy-MM-dd" // format: read date from string
if let date = data["date"].flatMap({ args.formatter.date(from: $0)}) {
args.formatter.dateFormat = "MMMM" // format: read month (as string) from date
let month = args.formatter.string(from: date)
args.result[month] = args.result[month, default: []] + [data]
}
}.result
Further nesting the result one more level into the value for a "month" key in a [String: [String : [[String : String]]]] is straight-forward:
let categorizedData = ["month": monthCategorizedData]
print(categorizedData)
/* ["month": ["January": [["date": "2018-01-01", "name": "New Year"],
["date": "2018-01-31", "name": "Public holiday"]],
"February": [["date": "2018-02-14", "name": "Valentine\'s Day"],
["date": "2018-02-28", "name": "Public Holiday"]]]] */

Answer 2

Dictionary has a method init(grouping:by:) which can do that in a pretty smart way.
Then date parameter is converted to Date and then to the month name with a DateFormatter
let array = [["date": "2018-01-01", "name": "New Year"],
["date": "2018-01-31", "name": "Public holiday"],
["date": "2018-02-14", "name": "Valentine's Day"],
["date": "2018-02-28", "name": "Public Holiday"]]
let dictionary = Dictionary(grouping: array) { (item) -> String in
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd"
guard let dateString = item["date"],
let date = formatter.date(from: dateString) else { return "Unknown" }
formatter.dateFormat = "MMMM"
return formatter.string(from: date)
}
print(["months" : dictionary])

Answer 3

while im not expert but problem for me seem to be just how u get from
"date" = "year-month-day" the value of month
if u could be able to some how cut? or get just 5th and 6th character it will become a number of month u need
based on that u could use if or switch and make an array of dictionaries
or even just dictionaries which u would then add into array as u wish.
so after getting this month number it would be like this :
var dict: [String: [[String:String]]] = [:]
dict["janury"] = [["2012-01-12":"Event"],["2012-01-13":"event2"]]
if monthNumber == 1 {
dict["janury"]?.append(["2012-01-14":"event3"])
}
and then for each month u would need new if total of 12 eventually switch with 12 statements
as for how to get this value of string i don't know yet, but i'm almost sure google could help it or someone with better experience than my