I want to check if the first three characters entered in the UI Textfield are numbers. I could do this easily in Python, but for some reason in Swift it's a pain.
Here's my python if statements (which I want to 'translate' into swift as it works):
str = "123abc"
if str.isdigit():
if str[:3]:
print(str)
and here's my swift code
#IBOutlet weak var input: UITextField!
#IBAction func checkBarcodeRegion(_ sender: UIButton)
{
let text: String = input.text!
if text.prefix(3)
{
//if numeric
//do something
}
}
Can't get this to work. Any help appreciated.
Three alternatives:
Create an Int from the substring and check if for non-nil.
let isNumeric1 = Int(text.prefix(3)) != nil
Remove all digits from the substring with Regular Expression and check for empty string
let isNumeric2 = text.prefix(3).replacingOccurrences(of: "[0-9]", with: "", options: .regularExpression).isEmpty
Split the substring by the decimalDigits character set and check if the number of components is 4
let isNumeric3 = text.prefix(3).components(separatedBy: .decimalDigits).count == 4
Using prefix is the right direction to go. You can use allSatisfy after that to check if they are all digits. One of the ways to check for digits is to check if the unicode scalar is in the CharacterSet.decimalDigits set.
text.unicodeScalars.prefix(3)
.allSatisfy(CharacterSet.decimalDigits.contains)
This will check for all the digits in Unicode, including the ones that the Indians and Arabic use.
If by digits you mean the ASCII 0123456789, then you could use:
text.prefix(3).allSatisfy(("0"..."9").contains)
Related
I'm looking for a way to take a String and extract Emoji characters.
I know that Emojis are part of Unicode so I need to remove a certain subset of Unicode characters. I don't really know where to start.
The Set of Emoji characters
First of all we need a Set containing the unicode values representing the emoji.
Disclaimer
For this answer I am using the range of Emoticons (1F601-1F64F) and Dingbats (2702-27B0) to show you the solution. However keep in mind that you should add further ranges depending on your needs.
Extending Character
Now we need a way to calculate the Unicode Scalar Code Point of a Character. For this I am using the solution provided here.
extension Character {
private var unicodeScalarCodePoint: Int {
let characterString = String(self)
let scalars = characterString.unicodeScalars
return Int(scalars[scalars.startIndex].value)
}
}
Extending String
This extension does allow you to extract the emoji characters from a String.
extension String {
var emojis:[Character] {
let emojiRanges = [0x1F601...0x1F64F, 0x2702...0x27B0]
let emojiSet = Set(emojiRanges.flatten())
return self.characters.filter { emojiSet.contains($0.unicodeScalarCodePoint) }
}
}
Testing
let sentence = "๐ hello world ๐"
sentence.emojis // ["๐", "๐"]
I entered a two emojis in textfield ๐จโ๐จโ๐งโ๐ง๐, here I'm getting total number of 5 characters length whereas 4 characters for first emoji and 1 character for second. Looks like apple has combined 4 emojis to form a one.
I'm looking for the swift code where I can separate each of emojis separately, suppose by taking the above example I should be getting 2 strings/character separately for each emoji.
Can any one help me to solve this, I've tried many things like regex separation or componentsSeparatedByString or characterSet. but unfortunately ended up with negative.
Thanks in advance.
Update for Swift 4 (Xcode 9)
As of Swift 4 (tested with Xcode 9 beta) a "Emoji ZWJ Sequence" is
treated as a single Character as mandated by the Unicode 9 standard:
let str = "๐จโ๐จโ๐งโ๐ง๐"
print(str.count) // 2
print(Array(str)) // ["๐จโ๐จโ๐งโ๐ง", "๐"]
Also String is a collection of its characters (again), so we can
call str.count to get the length, and Array(str) to get all
characters as an array.
(Old answer for Swift 3 and earlier)
This is only a partial answer which may help in this particular case.
"๐จโ๐จโ๐งโ๐ง" is indeed a combination of four separate characters:
let str = "๐จโ๐จโ๐งโ๐ง๐" //
print(Array(str.characters))
// Output: ["๐จโ", "๐จโ", "๐งโ", "๐ง", "๐"]
which are glued together with U+200D (ZERO WIDTH JOINER):
for c in str.unicodeScalars {
print(String(c.value, radix: 16))
}
/* Output:
1f468
200d
1f468
200d
1f467
200d
1f467
1f60d
*/
Enumerating the string with the .ByComposedCharacterSequences
options combines these characters correctly:
var chars : [String] = []
str.enumerateSubstringsInRange(str.characters.indices, options: .ByComposedCharacterSequences) {
(substring, _, _, _) -> () in
chars.append(substring!)
}
print(chars)
// Output: ["๐จโ๐จโ๐งโ๐ง", "๐"]
But there are other cases where this does not work,
e.g. the "flags" which are a sequence of "Regional Indicator
characters" (compare Swift countElements() return incorrect value when count flag emoji). With
let str = "๐ฉ๐ช"
the result of the above loop is
["๐ฉ", "๐ช"]
which is not the desired result.
The full rules are defined in "3 Grapheme Cluster Boundaries"
in the "Standard Annex #29 UNICODE TEXT SEGMENTATION" in the
Unicode standard.
You can use this code example or this pod.
To use it in Swift, import the category into the YourProject_Bridging_Header
#import "NSString+EMOEmoji.h"
Then you can check the range for every emoji in your String:
let example: NSString = "๐จโ๐จโ๐งโ๐ง๐" // your string
let ranges: NSArray = example.emo_emojiRanges() // ranges of the emojis
for value in ranges {
let range:NSRange = (value as! NSValue).rangeValue
print(example.substringWithRange(range))
}
// Output: ["๐จโ๐จโ๐งโ๐ง", "๐"]
I created an small example project with the code above.
For further reading, this interesting article from Instagram.
I am making calculator in Swift. Stuck in backspace button. If user press wrong digit then backspace button would help to delete digit off the display.
Though I wrote dropLast function and works. It return appropriate result. How to use count method, don't understand the return type of count method.
#IBOutlet weak var display: UILabel!
#IBAction func backspace() {
//how to use count method to check collection of elements
//dropLast drop the last digit and display result
let dropedDigit = dropLast(display.text!)
display.text = dropedDigit
}
How about something like this:
private func dropLast(text: String) -> String {
let endIndex = advance(text.endIndex, -1)
return text.substringToIndex(endIndex)
}
It calculates the index where you want to make the cut (endIndex of text - 1) and then returns the substring to this index. This function should drop the last character.
I am not using count method here, but for you reference Swift 1.2 introduces count(<#x: T#>) method that calculates length of sets including Strings.
I know this thread is outdated, but I just went through the process of making this work, myself, in Swift 2.2, and figured I could help answer it.
#IBAction func delButton(sender: AnyObject) {
if display.text != nil {
var tempString = Array(display.text!.characters)
tempString.removeLast(1)
display.text = ""
for num in 0..<tempString.count {
display.text = display.text! + String(tempString[num])
}
}
}
Basically, we're checking to see that the display label has stuff in it, so we don't throw an error, and if so, making a variable in the scope of the function to hold the label's characters individually in a string. After that, we remove the last character from the array, clear out the label to ensure we aren't adding what's already there to our new values, then iterating through the updated array of characters and adding it to the label.
It's important to note that we are casting the values contained in the array as String, because they've been put into the array as character values, which operate differently than the string value the label is expecting.
Like I said, I know the thread is a little out of date, but I've been going through courses in Swift, and have discovered that while there is a plethora of information out there for Objective-C, there is perilously little information out there for how to do a lot of those things in Swift. Since the language is being updated repeatedly, I've noticed a growing divide between the two languages.
In a UITableView, I'm listing a bunch of languages to be selected. And to put a section index view to the right like in Contacts app, I'm getting all first letters of languages in the list and then use it to generate the section index view.
It works almost perfect, Just I encountered with a problem in getting first letter of some strings in Hebrew. Here a screenshot from playground, one of the language name that I couldn't get the first letter:
Problem is, the first letter of the name of the language that has "ina" language code, isn't "ื", it's an empty character; it's not a space, it's just an empty character. As you can see, it's actually 12 characters in total, but when I get count of it, it says 13 characters because there is an non-space empty character in index 0.
It works perfectly if I use "eng" or "ara" languages with putting these values in value: parameter. So maybe the problem is cause of system that returns a language name with an empty character in some cases, I don't know.
I tried some different methods of getting first letter, but any of it didn't work.
Here "ื" isn't the first letter, it's the second letter. So I thought maybe I can find a simple hack with that, but I want to try solving it before trying workarounds.
Here is the code:
let locale = NSLocale(localeIdentifier: "he")
let languageName = locale.displayNameForKey(NSLocaleIdentifier, value: "ina")!
let firstLetter = first(languageName)!
println(countElements(languageName))
for character in languageName {
println(character)
}
You could use an NSCharacterSet.controlCharacterSet() to test each character. I can't figure out how to stay in Swift-native strings, but here's a function that uses NSString to return the first non-control character:
func firstNonControlCharacter(str: NSString) -> String? {
let controlChars = NSCharacterSet.controlCharacterSet()
for i in 0..<str.length {
if !controlChars.characterIsMember(str.characterAtIndex(i)) {
return str.substringWithRange(NSRange(location: i, length: 1))
}
}
return nil
}
let locale = NSLocale(localeIdentifier: "he")
let languageName = locale.displayNameForKey(NSLocaleIdentifier, value: "ina")!
let firstChar = firstNonControlCharacter(languageName) // Optional("ื")
I have an issue with converting character type to String type. First of all, I have below extension of String for finding nth character within String.
extension String {
func characterAtIndex(index: Int) -> Character? {
var cur = 0
for char in self {
if cur == index {
return char
}
cur++
}
return nil
}
}
I get what I want with this class extension. However when I use that nth character for title of my custom UIButton, gives an error. My Uibutton Class is
class hareketliHarfler: UIButton {
init(frame: CGRect) {
super.init(frame: frame)
// Initialization code
}
func getLetter(letter:String!){
self.titleLabel.text = letter
}
}
The error show when i try to access "getLetter(letter:String)" function. Here is example of main view Controller codes:
var harfim = hareketliHarfler(frame: CGRectMake(100,100,100,100))
var str="This is my String"
var bufi=str.characterAtIndex(3)
harfim.getLetter(bufi as AnyObject) ****
In * section I try .getLetter(bufi), .getLetter(bufi as String) also I try to change parameter type of function. Look like: func getLetter(letter:Character!) or func getLetter(letter:AnyObject!)...etc
Didn't find a way. Need a help on that. Thank you
How about the simple
String(theCharacter)
Works in Swift 4 and Swift 5
Your problem is quite simple: your characterAtIndex function returns a Character, and self.titleLabel.text is a String. You can't convert between the two implicitly. The easiest way would be to turn the Character into a String using the String initialiser:
// ch will be Character? type.
if let ch = str.characterAtIndex(3) {
// Initialise a new String containing the single character 'ch'
harfim.getLetter(String(ch))
} else {
// str didn't have a third character.
}
Unlike other solutions, this is safe for unusual Unicode characters, and won't initialise a potentially large array or iterate the whole String just to get the third character.
Change this:
var bufi=str.characterAtIndex(3)
harfim.getLetter(bufi as AnyObject)
to this:
harfim.getLetter(String(Array(str)[3]))
So what happening here:
we create an array from our string. Array elements are symbols from original string. Such break down correctly tracks symbols that are presented with a sequences of two or more code points. E.g. emoji or flag as noted by #MartinR.
We access element at 4-th position.
Note that as we crate an array from initial string then performance wise is better to use this method only with short strings and avoid it in oft-repeated routines. But in your case it seems to be OK.
Can also use Character(text).isNumber if you want to get localised numbers.
Reference:
https://developer.apple.com/documentation/swift/character/3127015-isnumber