Question 69354 in IOS Swift Question posted in
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Why Is My Array Index Out Of Range Using An If Statement? – Ios swift

This is the code:

func setTimeArray() {
    let iStart = Int(Double(selectedStart)! * 0.01)
    var index = iStart
    var tempArray: Array<String> = []

    print("count is ", count)
    for i in 0..<self.count  {
        var theHours = ""
        if (index == 24) {
           index = 0
        }  else if (index == 23) {
            theHours = self.parse24(theString: String(index)) + " to " + self.parse24(theString: "0")
        } else {
            theHours = self.parse24(theString: String(index)) + " to " + self.parse24(theString: String(index + 1))
        }
        tempArray.insert(theHours, at: i)
        index = index + 1
    }
    self.timeArray = tempArray
}

This code works just fine, but I need to wrap the place where it inserts into the tempArray so that it doesn’t add an empty string. Unfortunately, when I try to add an if statement, or place tempArray.insert(theHours, at: i) inside the already existing if statements, I get the error: "Swift/Array.swift:405: Fatal error: Array index is out of range"

I mean, I’m actually adding more items without the if statement! Can anyone tell me how to fix this?

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2

Answers


  1. 0

    When you look at the documentation of the insert function, it says the following about the i parameter:

    i

    The position at which to insert the new element. index must be a valid index of the array or equal to its endIndex property.

    You need to insert the element to an existing index or add it to the end of the array. It might help to add a print statement to print index, i and the array you are inserting it in to see what is exactly going on.

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  2. 0

    Still a bit confusing, but I think I understand what you’re going for…

    Suppose count is 5 …

    If it is 10 o’clock, you want an array result of:

    [10:00 to 11:00]
[11:00 to 12:00]
[12:00 to 13:00]
[13:00 to 14:00]
[14:00 to 15:00]

    If it is 15 o’clock, you want an array result of:

    [15:00 to 16:00]
[16:00 to 17:00]
[17:00 to 18:00]
[18:00 to 19:00]
[19:00 to 20:00]

    If it is 22 o’clock, you want it to "wrap around" and get an array result of:

    [22:00 to 23:00]
[23:00 to 0:00]
[0:00 to 1:00]
[1:00 to 2:00]
[2:00 to 3:00]

    (your self.parse24(theString: String(index)) may be formatting it a little different).

    If that’s the case, take a look at this:

        var tempArray: Array<String> = []

    // no need for an "i" counter variable
    for _ in 0..<self.count  {
        var theHours = ""
        
        // if we're at 24, set index to 0
        if (index == 24) {
            index = 0
        }
        
        if (index == 23) {
            // if we're at 23, the string will be "23:00 to 0:00"
            theHours = "23:00 to 0:00"
        } else {
            // the string will be "index to index+1"
            theHours = "(index):00 to (index+1):00"
        }
        // don't use insert, just append the new string
        //tempArray.insert(theHours, at: i)
        tempArray.append(theHours)
        
        index = index + 1
    }
    
    self.timeArray = tempArray

    Edit

    It’s probably important that you understand why you were getting the Array index is out of range error.

    You still didn’t post the code that was causing the error, but I’m guessing it is something like this:

        for i in 0..<self.count  {
        var theHours = ""
        if (index == 24) {
            index = 0
        }  else if (index == 23) {
            theHours = self.parse24(theString: String(index)) + " to " + self.parse24(theString: "0")
        } else {
            theHours = self.parse24(theString: String(index)) + " to " + self.parse24(theString: String(index + 1))
        }
        
        if theHours.isEmpty {
            // don't add the empty string to the array
        } else {
            // add it to the array
            tempArray.insert(theHours, at: i)
        }
        
        index = index + 1
    }

    So, if we start at 22 o’clock, and count equals 5, your code does this:

    i equals 0
index equals 22
theHours = "22 to 23"
insert string at [i]  // i is 0
increment index
increment i

i now equals 1
index now equals 23
theHours = "23 to 0"
insert string at [i]  // i is 1
increment index
increment i

i now equals 2
index now equals 24
    set index to 0
theHours = ""
DON'T insert empty string
increment i

i now equals 3
index now equals 0
theHours = "0 to 1"
insert string at [i]  // i is 3

*** ERROR ***

    You get the out of range error because you didn’t insert the empty string at [2], but i keeps incrementing.

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