I can't understand the in label of utf16Offset(in:) statement
what the use of this label.
And can anyone explain that,
Is the following statement is right or wrong?
let location = textString.range(of: hyperText)?.lowerBound.utf16Offset(in: textString)
you code is correct.it means the offset into a string's code units for this index.
for example:
var textString = "niaddjkdskjdsjdsk"
let location = textString.range(of: "dd")?.lowerBound.utf16Offset(in: textString)
as we know, the bound is (3,_),so the utf16Offset is 3.
Before Swift 4.2,we use encodedOffset,now it replace by utf16Offset, they are same behavior
Related
I have some code which is supposed to find the first and final coordinate in an MGLPolyline. Currently, I am able to find the first and the middle value, but am not able to find the last value. Bellow is my code. In it, you can see how I find the first and middle coordinate.
var arrayOfCoordinates = [CLLocationCoordinate2D]()
var arrayOfPolylines = [MGLPolyline]()
for value in arrayOfPolylines {
mapView.addAnnotation(value)
//This is for the first and last snakehead and tail stuff
let lastLoc = value.coordinate.latitude
let newLoc = value.coordinate.longitude
let firstCor = value.coordinates[0].latitude
let secondCor = value.coordinates[0].longitude
...
I have tried the following to find the value:
value.coordinates[value.coordinates.count] //This does not compile as it says
Value of type 'UnsafeMutablePointer' has no member 'count'
So my question is how can I find the last value (coordinate)?
Well, your code will not work for this. With the current code, you would not be able to find the last value easily, you would have to do a mathematical process to determine the count of coordinates then check if the for loop has run through enough time to reach the last coordinate.
But an easier way is to create instead an array of CLLocation which then you can access with the following code:
let lastLoc = self.arrayOfLocationList.last //last value here
let newLoc = self.arrayOfLocationList.first
I'm trying to create a substring of the first 4 characters entered in a textField in Swift 4 on my iOS app.
Since the change to Swift 4 I'm struggling with basic String parsing.
So based on Apple documentation I'm assuming I need to use the substring.index function and I understand the second parameter (offsetBy) is the number of characters to create a substring with. I'm just unsure how I tell Swift to start at the beginning of the string.
This is the code so far:
let postcode = textFieldPostcode.text
let newPostcode = postcode?.index(STARTATTHEBEGININGOFTHESTRING, offsetBy: 4)
I hope my explanation makes sense, happy to answer any questions on this.
Thanks,
In Swift 4 you can use
let string = "Hello World"
let first4 = string.prefix(4) // Hell
The type of the result is a new type Substring which behaves very similar to String. However if first4 is supposed to leave the current scope – for example as a return value of a function – it's recommended to create a String explicitly:
let first4 = String(string.prefix(4)) // Hell
See also SE 0163 String Revision 1
In Swift 4:
let postcode = textFieldPostcode.text!
let index = postcode.index(postcode.startIndex, offsetBy: 4)
let newPostCode = String(postcode[..<index])
Can anyone tell me why the code below works in Swift 2, but somehow breaks in Swift 3?
let range: Range = 0...2
However it can simply be fixed by doing this
let range: Range = 0..<3
Anyone knows what is the reason behind this?
Operators ... and ..< used to produce the same type, Range, in Swift 2.x. Now they produce different types (migration guide):
Range
CountableRange
ClosedRange
CountableClosedRange
Changing the type in the first assignment to ClosedRange should fix the problem. Better yet, let Swift infer the type for you:
let range = 0...2
I have a function that finds the current word a user has selected in a UITextView. However, if I call this function when an emoji is in the UITextView.text property, I see a crash. I believe this is because of the different character counts in String vs NSString.
How do I properly convert this?
func currentWord() -> String {
let cursorPosition = selectedRange.location
let separationCharacters = NSCharacterSet(charactersInString: " ")
// crash occurs here
let beginRange = Range(text.startIndex.advancedBy(0) ..< text.startIndex.advancedBy(cursorPosition))
let endRange = Range(text.startIndex.advancedBy(cursorPosition) ..< text.startIndex.advancedBy(text.characters.count))
let beginPhrase = text.substringWithRange(beginRange)
let endPhrase = text.substringWithRange(endRange)
let beginWords = beginPhrase.componentsSeparatedByCharactersInSet(separationCharacters)
let endWords = endPhrase.componentsSeparatedByCharactersInSet(separationCharacters)
return beginWords.last! + endWords.first!
}
I believe this is because of the different character counts in String vs NSString
You're right about that. You are shifting back and forth between using NSRange (Cocoa) and Range (Swift) — and they work differently. And NSString (Cocoa) and String (Swift) have different ideas of where the character boundaries are. You need to be consistent.
Once you've used selectedRange in the first line, you are in the Cocoa world of NSRange. You need to stay consistently in the Cocoa world. Don't use any Swift Ranges! Don't use any Swift characters!
Form your beginRange entirely using NSRange — for example, call NSMakeRange. Don't use characters.count; stay in the NSString world and use the string's length (in Swift, that is its utf16.count). Then all will be well.
I'm trying to make the words split by spaces green in a UITextField, kind of like the way it works when you compose of a new iMessage. I commented out the part of my code that's giving me a runtime error. Please let me know if you have any ideas:
func textChanged(sender : UITextField) {
var myMutableString = NSMutableAttributedString()
let arr = sender.text!.componentsSeparatedByString(" ")
var c = 0
for i in arr {
/*
myMutableString.addAttribute(NSForegroundColorAttributeName, value: UIColor.greenColor(), range: NSRange(location:c,length:i.characters.count))
sender.attributedText = myMutableString
*/
print(c,i.characters.count)
c += i.characters.count + 1
}
}
Your code has at least two parts needed to be fixed.
var myMutableString = NSMutableAttributedString()
This line creates an empty NSMutableAttributedString. Any access to the content may cause runtime error.
The other is i.characters.count. You should not use Character based locations and counts, when the APIs you want use is based on the behaviour of NSString. Use UTF-16 based count.
And one more, this is not critical, but you should use sort of meaningful names for variables.
So, all included:
func textChanged(sender: UITextField) {
let text = sender.text ?? ""
let myMutableString = NSMutableAttributedString(string: text)
let components = text.componentsSeparatedByString(" ")
var currentPosition = 0
for component in components {
myMutableString.addAttribute(NSForegroundColorAttributeName, value: UIColor.greenColor(), range: NSRange(location: currentPosition,length: component.utf16.count))
sender.attributedText = myMutableString
print(currentPosition, component.utf16.count)
currentPosition += component.utf16.count + 1
}
}
But whether this works as you expect or not depends on when this method is called.
You create an empty attributed string but never install any text into it.
The addAttribute call apples attributes to text in a string. If you try to apply attributes to a range that does not contain text, you will crash.
You need to install the content of the unattributed string into the attributed string, then apply attributes.
Note that you should probably move the line
sender.attributedText = myMutableString
Outside of your for loop. There is no good reason to install the attributed string to the text field repeatedly as you add color attributes to each word.
Note this bit from the Xcode docs on addAttribute:
Raises... an NSRangeException if any part of aRange lies beyond the
end of the receiver’s characters.
If you are getting an NSRangeException that would be a clue as to what is wrong with your current code. Pay careful attention to the error messages you get. They usually offer important clues as to what's going wrong.