I am puzzled. I need to compare product date codes. they look like 12-34-56. I wrote some code to break the parts up and compare them. this code works fin in the play ground. But when i make it a function in a view controller values come up NIL and i get a lot of "Optional("12-34-56")" values when printed to the log or viewed in a break. I tried unwrapping in many locations but nothing takes.? don't be confused by the variables date and month because they are not product codes can have 90 days and 90 months depending on the production machine used.
func compaireSerial(oldNumIn: NSString, newNumIn: String) -> Bool {
// take the parts of the number and compare the pics on at a time.
// Set up the old Num in chunks
let oldNum = NSString(string: oldNumIn)
let oldMonth = Int(oldNum.substringToIndex(2))
let oldDay = Int(oldNum.substringWithRange(NSRange(location: 3, length: 2)))
let oldYear = Int(oldNum.substringFromIndex(6))
print(oldMonth,oldDay, oldYear)
// Set up the new Num in chunks
let newNum = NSString(string: newNumIn)
let newMonth = Int(newNum.substringToIndex(2))
let newDay = Int(newNum.substringWithRange(NSRange(location: 3, length: 2)))
let newYear = Int(newNum.substringFromIndex(6))
print(newMonth, newDay, newYear)
// LETS Do the IF comparison steps.
if oldYear < newYear {
return true
} else if oldMonth < newMonth {
return true
} else if oldDay < newDay {
return true
} else {
return false
}
}
May thanks to any one. Im totally stumped
All Int() initializers with String parameters return always an optional Int.
The realtime result column in a Playground doesn't indicate the optional but printing it does.
let twentyTwo = Int("22") | 22
print(twentyTwo) | "Optional(22)\n"
I don't see how i can delete my question so ill post this to let others know it is fixed. Turns out the auction works okay but the NSUserDefaults value coming in was optional. So i was feeding the optional in. After unwrapping the NSUser value all works.
Related
Trying to make a func that will count characters in between two specified char like:
count char between "#" and "." or "#" and ".com"
If this is only solution could this code be written in a simple way with .count or something less confusing
func validateEmail(_ str: String) -> Bool {
let range = 0..<str.count
var numAt = Int()
numDot = Int()
if str.contains("#") && str.contains(".") && str.characters.first != "#" {
for num in range {
if str[str.index(str.startIndex, offsetBy: num)] == "#" {
numAt = num
print("The position of # is \(numAt)")
} else if
str[str.index(str.startIndex, offsetBy: num)] == "." {
numDot = num
print("The position of . is \(numDot)")
}
}
if (numDot - numAt) > 1 {
return true
}
}
return false
}
With help from #Βασίλης Δ. i made a direct if statement for func validateEmail that check if number of char in between are less than 1
if (str.split(separator: "#").last?.split(separator: ".").first!.count)! < 1{
return false
}
It could be usefull
There are many edge cases to what you're trying to do, and email validation is notoriously complicated. I recommend doing as little of it as possible. Many, many things are legal email addresses. So you will need to think carefully about what you want to test. That said, this addresses what you've asked for, which is the distance between the first # and the first . that follows it.
func lengthOfFirstComponentAfterAt(in string: String) -> Int? {
guard
// Find the first # in the string
let firstAt = string.firstIndex(of: "#"),
// Find the first "." after that
let firstDotAfterAt = string[firstAt...].firstIndex(of: ".")
else {
return nil
}
// Return the distance between them (not counting the dot itself)
return string.distance(from: firstAt, to: firstDotAfterAt) - 1
}
lengthOfFirstComponentAfterAt(in: "rob#example.org") // Optional(7)
There's a very important lesson about Collections in this code. Notice the expression:
string[firstAt...].firstIndex(of: ".")
When you subscript a Collection, each element of the resulting slice has the same index as in the original collection. The returned value from firstIndex can be used directly to subscript string without offsetting. This is very different than how indexes work in many other languages, and allows powerful algorithms, and also creates at lot of bugs when developers forget this.
Very new to Swift concepts and I'm having trouble conceptualizing how to convert a long decimal value type var distance: String? into a shorter one. This code is crashing due to a:
Fatal error: Unexpectedly found nil while unwrapping an Optional value
let distance = Int(item.distance!) // long decimal value
let x = Float((distance)!)
let y = Double(round(1000*x)/1000)
print(y)
A couple of observations:
You should not only excise the Int from your code snippet, but the Float, too. If your numbers can be large, Float can impose undesirable limitations in the precision of your calculation. So, you would likely want to remove both Int and Float like so:
guard let string = item.distance, let value = Double(string) else {
return
}
let result: Double = (value * 1000).rounded() / 1000
If you’re doing this rounding just so you can show it to 3 decimal places in your UI, you probably wouldn’t round the value at all, but rather just round the output using a NumberFormatter, e.g.:
let formatter = NumberFormatter()
formatter.numberStyle = .decimal
formatter.minimumFractionDigits = 3
formatter.maximumFractionDigits = 3
guard let string = item.distance, let value = Double(string) else {
return
}
let result: String = formatter.string(for: value)
We do this when showing fractional values in our UI because:
The resulting string will be “localized”. This is important because not all locales use . for the decimal point (e.g., in many countries, the value ½ is displayed as 0,5, not 0.5). We always want to show numbers in our UI in the manner preferred by the user. The NumberFormatter does all of this localization of string representations of numbers for us.
If the value had trailing zeros, the above formatter will generate all of those decimal places (e.g. 0.5 will be shown as 0.500), which is often preferable when dealing with decimal places in your UI. (And even if if you don’t want those trailing zeros, you’d still use the NumberFormatter and just set minimumFractionDigits to whatever is appropriate for your app.)
If you really need to round the number to three decimal places (which is unlikely in this case, but we encounter this in financial apps), you shouldn’t use Double at all, but rather Decimal. Again, I’m guessing this is unlikely in your scenario, but I mention it for the sake of completeness.
First of all, This will help you find the issue:
if let distance = item.distance {
if let distanceInt = Int(distance) {
let x = Float(distanceInt)
let y = Double(round(1000*x)/1000)
print(y)
} else {
print("Distance (\(distance)) is not convertible to Int. It has a value, but this value is not representing an integer number.")
}
} else {
print("distance is nil. It should be some number but it is not set yet")
}
Here you can see this string: "0.45991480288961" can not be converted to an Int. So you need to convert it directly to a Double:
if let distance = item.distance {
if let distanceDouble = Double(distance) {
let x = Float(distanceDouble)
let y = Double(round(1000*x)/1000)
print(y)
} else {
print("Distance (\(distance)) is not convertible to Double. It has a value, but this value is not representing a double number.")
}
} else {
print("distance is nil. It should be some number but it is not set yet")
}
[MacOS 10.14.1, Xcode 10.1, Swift 4.2]
I'm working on creating a getopt style CLI argument processor whilst practising Swift. In my design, I decided to create a computed variable, represented as a [String:Bool] dictionary, that can be checked to see if an option (key) is just a switch (value = true) or whether it may include parameters (value = false). So I've written the code below, all of which is, at the moment, in my small (300 lines) main.swift file.
The code works correctly in a playground, but in my Swift Xcode project, whilst the dictionary's keys are correct, values are always false and inconsistent with the printed messages.
let options = "cwt:i:o:"
//lazy var optionIsSwitch : [String:Bool] = { (This will be moved to a class)
var optionIsSwitch : [String:Bool] = {
var tmpOptionIsSwitch : [String:Bool] = [:]
let optionsStrAsArray = Array(options)
let flags = Array(options.filter { !":".contains($0) } )
tmpOptionIsSwitch.reserveCapacity(flags.count)
for thisOption in 0...flags.count-1 {
var posInOptionsStr = 0
while posInOptionsStr < optionsStrAsArray.count-1 && flags[thisOption] != optionsStrAsArray[posInOptionsStr] {
posInOptionsStr += 1
}
if posInOptionsStr < optionsStrAsArray.count-1 && optionsStrAsArray[posInOptionsStr+1] == ":" {
tmpOptionIsSwitch[String(flags[thisOption])] = false
print("\(flags[thisOption]) is FALSE")
} else {
tmpOptionIsSwitch[String(flags[thisOption])] = true
print("\(flags[thisOption]) is TRUE")
}
}
return tmpOptionIsSwitch
}()
I've stepped through the code in my project to observe the execution sequence, and found it to be correct. As per the first image, tmpOptionIsSwitch returns a dictionary containing the right keys but all the values are set to false, which is inconsistent with the print statements.
As part of my debugging activities, I copied the above code into a Swift Playground where I found it gave the correct results, as per the image below.
Has anyone has such an issue? Is there something I've done wrong?
Using Swift, I'm trying to take a list of numbers input in a text view in an app and create a sum of this list by extracting each number for a grade calculator. Also the amount of values put in by the user changes each time. An example is shown below:
String of: 98,99,97,96...
Trying to get: 98+99+97+96...
Please Help!
Thanks
Use components(separatedBy:) to break up the comma-separated string.
Use trimmingCharacters(in:) to remove spaces before and after each element
Use Int() to convert each element into an integer.
Use compactMap (previously called flatMap) to remove any items that couldn't be converted to Int.
Use reduce to sum up the array of Int.
let input = " 98 ,99 , 97, 96 "
let values = input.components(separatedBy: ",").compactMap { Int($0.trimmingCharacters(in: .whitespaces)) }
let sum = values.reduce(0, +)
print(sum) // 390
For Swift 3 and Swift 4.
Simple way: Hard coded. Only useful if you know the exact amount of integers coming up, wanting to get calculated and printed/used further on.
let string98: String = "98"
let string99: String = "99"
let string100: String = "100"
let string101: String = "101"
let int98: Int = Int(string98)!
let int99: Int = Int(string99)!
let int100: Int = Int(string100)!
let int101: Int = Int(string101)!
// optional chaining (if or guard) instead of "!" recommended. therefore option b is better
let finalInt: Int = int98 + int99 + int100 + int101
print(finalInt) // prints Optional(398) (optional)
Fancy way as a function: Generic way. Here you can put as many strings in as you need in the end. You could, for example, gather all the strings first and then use the array to have them calculated.
func getCalculatedIntegerFrom(strings: [String]) -> Int {
var result = Int()
for element in strings {
guard let int = Int(element) else {
break // or return nil
// break instead of return, returns Integer of all
// the values it was able to turn into Integer
// so even if there is a String f.e. "123S", it would
// still return an Integer instead of nil
// if you want to use return, you have to set "-> Int?" as optional
}
result = result + int
}
return result
}
let arrayOfStrings = ["98", "99", "100", "101"]
let result = getCalculatedIntegerFrom(strings: arrayOfStrings)
print(result) // prints 398 (non-optional)
let myString = "556"
let myInt = Int(myString)
First off, I'm fairly new to programming and trying to learn Swift, though I've worked with python and perl in the past.
I'm creating a simple prime number command line application. The program runs correctly when I provide the arguments for the functions, but causes consistently incorrect outputs when I prompt user input. I researched the best way to implement this behavior in Swift, as it doesn't have scanf() or raw_input() type commands, but I have something screwed up.
The program has several different functions, but the one I've been fighting with checks whether an integer is prime. The code for the function follows:
func testForPrime(num:Int)->Bool{
var num = num
var counter = 0
var primeTest : Bool = true
if num <= 1 || num % 2 == 0{
println("\(num) is not a prime number")
primeTest = false
}else{
##'checkerNumbers' is another function to determine the denominator
for i in checkerNumbers(Double(num)){
if num % i == 0 {
++counter
println("\(num) is not a prime number.")
println("\(num / i)*\(i)=\(num)")
primeTest = false
break
}
}
if counter == 0{
println("\(num) is a prime number!")
primeTest = true
}
}
return primeTest
}
And here is the input for the function:
var input = NSFileHandle.fileHandleWithStandardInput()
println("Enter a number to check if it is prime")
if let data : NSData = input.availableData as NSData? {
if let var x : Int = NSInteger(NSUTF8StringEncoding) as NSInteger?{
var intInput = x
testForPrime(intInput)
}
}
When a any number is entered in the terminal, the output is always '4'. However, if I run the function with testForPrime(13), instead of with user input, it responds as I would expect. I was thinking it may have to do with the conversion from NSString and NSUTF8StringEncoding to Int...
Can someone help me sort this out?
Thanks in advance!
Ok... So I figured out a way to make it work, though it may not be the best. I replaced the whole input section with the following:
println("Enter a number to check if it is prime")
var input = NSString(data: NSFileHandle.fileHandleWithStandardInput().availableData, encoding:NSUTF8StringEncoding)
var intInput = input?.intValue
testForPrime(Int(intInput!))