get a array of weekdays intager to a string using weekdaysymbol-CodePudding

I am trying to print an array of weekdays using the weekdaysymbol - here is my code so far

for i in Weekdaysnumbers {
            
            let calender = Calendar.current
            let weekdayIndex = ((Weekdaysnumbers[i!]! - 1)   (calender.firstWeekday - 1)) % 7
            varWeekdaysStrings.append(calender.shortWeekdaySymbols[weekdayIndex])
        }

The Weekdaysnumbers stores an array of a weekday integers that the user gets to set. I then want to print a string representing it. I set it inside a for loop that goes through the array of Weekdaysnumbers and appends it to the new array. But I get this error message

 Thread 1: Fatal error: Index out of range

how can I get rid of this error? Any help would be great.

CodePudding user response：

Your code makes no sense.

the line for i in Weekdaysnumbers {

Gives you a loop where on each iteration, i will contain sequential values from your Weekdaysnumbers array.

Using Weekdaysnumbers[i!] to try to index into Weekdaysnumbers with the value of i is wrong, and will likely crash with an array index out of bounds error like the one you report. i contains a value from the array, not an index into the array.

Also, do not use force-unwrap at all until you fully understand optionals. Think of the force-unwrap (!) operator as the "crash if nil" operator, because that's what it does.

As a final note not related to your crash, variable names in Swift should start with lower-case letters, and should use "camel case", so Weekdaysnumbers should be named weekdaysNumbers. (Type names and class names should start with an upper-case letter. variable names and function names should start with a lower case letter.) This is a strong convention in Swift.

CodePudding user response：

You should subtract 1 from the weekday calendar component value before accessing the shortWeekdaysSymbols array.

Values for the weekday calendar component ranges between 1…7 (for the Gregorian calendar) while the shortWeekdaysSymbols array is 0 based indexed.

CodePudding user response：

I figured out the answer - thanks to the help of @Duncan C I realize my mistake and I did the following to fix my code

for i in Weekdaysnumbers {
            
            switch i {
            case 1:
                varWeekdaysStrings.append("Sunday")
            case 2:
                varWeekdaysStrings.append("Monday")

            case 3:
                varWeekdaysStrings.append("Tuesday")

            case 4:
                varWeekdaysStrings.append("Wednesday")

            case 5:
                varWeekdaysStrings.append("Thursday")

            case 6:
                varWeekdaysStrings.append("Friday")

            case 7:
                varWeekdaysStrings.append("Saturday")

            
                
            default:
                print("error")

            }