Given year & month, how to check a particular day

问题:

I am trying to check if a particular day exists in a month or not. However unable to find anything of help. To give an example I tried below code in Playground;

var components = DateComponents()
components.month = 2
components.year = 2016
components.day = 30
components.calendar = Calendar.current

components.date

This gives the answer;

"Mar 1, 2016, 12:00 AM"

So what it does is it tries to manipulate with TimeZones and moves the needle. Hence I'm unable to find a way to check if a particular day exists in a given month & year. Can anyone please guide.

回答1:

DateComponents has an isValidDate property, which you can use for that purpose:

var components = DateComponents()
components.month = 2
components.year = 2016
components.day = 30
components.calendar = Calendar.current

print(components.isValidDate) // false

回答2:

Lets break this down to -

How to check number of days in a month-year?

Then your problem boils down to check if the given day is within the range [1, numDaysInMonthYear).

The code for above is this:

// Swift 2:
let range = calendar.rangeOfUnit(.Day, inUnit: .Month, forDate: date)
// Swift 1.2:
let range = calendar.rangeOfUnit(.CalendarUnitDay, inUnit: .CalendarUnitMonth, forDate: date)

let numDaysInMonthYear = range.length
print(numDaysInMonthYear) // 31

Credits: How do I find the number of days in given month and year using swift

回答3:

try this below method you can check the particular day exists in a month.

function checkDayIsExist(year:Int,month:Int,day:Int) -> Bool {

   let dateComponents = DateComponents(year: year, month: month)
   let calendar = Calendar.current
   let date = calendar.date(from: dateComponents)!

   let numberOfDays = calendar.range(of: .day, in: .month, for: date)!
   return numberOfDays.count >= day
}

Call by

print(checkDayIsExist(year:2017,month:7,day:31)) // true

回答4:

You can check by using NSDateFormatter / DateFormatter

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd MM yyyy"

let dateString = "30 02 2017"

if let date = dateFormatter.date(from: dateString)
{
  print("Date \(date)")   
}
else
{
  print("Date not existed")
}

You can change the date formatter's dateFormate based on your input string.