Why would this produce Elena instead of Paula?
let names = ["Paula", "Elena", "Zoe"]
var lastNameEndingInA: String?
for name in names.reversed() where name.hasSuffix("a") {
lastNameEndingInA = name
break
}
lastNameEndingInA // Optional("Elena")”
I would have thought that names.reversed() would be [“Zoe”, “Paula”, “Elena”] and then where name.hasSuffix(“a”) would skip “Zoe” and then go to “Paula” then break so lastNameEndingInA would be “Paula”?
I can’t figure out why it isn’t working like that though.
Your array is ["Paula", "Elena", "Zoe"]. When reversed it is ["Zoe", "Elena", "Paula"]. There is no reason to think it would be [“Zoe”, “Paula”, “Elena”]. So your code is working as expected.
But it can be written more easily as:
let lastNameEndingInA = names.reversed().first { $0.hasSuffix("a") }
It you want the names sorted in reverse and then find the match, do:
let lastNameEndingInA = names.sorted().reversed().first { $0.hasSuffix("a") }
Related
Ok, I am working in an iMessage app and am trying to parse more than 1 url query item from the selected message here- I have been successful getting/sending just 1 value in a query:
override func willBecomeActive(with conversation: MSConversation) {
// Called when the extension is about to move from the inactive to active state.
// This will happen when the extension is about to present UI.
if(conversation.selectedMessage?.url != nil) //trying to catch error
{
let components = URLComponents(string: (conversation.selectedMessage?.url?.query?.description)!)
//let val = conversation.selectedMessage?.url?.query?.description
if let queryItems = components?.queryItems {
// process the query items here...
let param1 = queryItems.filter({$0.name == "theirScore"}).first
print("***************=> GOT IT ",param1?.value)
}
}
When I just have 1 value, just by printing conversation.selectedMessage?.url?.query?.description I get an optional with that 1 value, which is good. But with multiple I cant find a clean way to get specific values by key.
What is the correct way to parse a URLQueryItem for given keys for iMessage?
When you do conversation.selectedMessage?.url?.query?.description it simply prints out the contents of the query. If you have multiple items then it would appear something like:
item=Item1&part=Part1&story=Story1
You can parse that one manually by splitting the string on "&" and then splitting the contents of the resulting array on "=" to get the individual key value pairs in to a dictionary. Then, you can directly refer to each value by key to get the specific values, something like this:
var dic = [String:String]()
if let txt = url?.query {
let arr = txt.components(separatedBy:"&")
for item in arr {
let arr2 = item.components(separatedBy:"=")
let key = arr2[0]
let val = arr2[1]
dic[key] = val
}
}
print(dic)
The above gives you an easy way to access the values by key. However, that is a bit more verbose. The way you provided in your code, using a filter on the queryItems array, is the more compact solution :) So you already have the easier/compact solution, but if this approach makes better sense to you personally, you can always go this route ...
Also, if the issue is that you have to write the same filtering code multiple times to get a value from the queryItems array, then you can always have a helper method which takes two parameters, the queryItems array and a String parameter (the key) and returns an optional String value (the value matching the key) along the following lines:
func valueFrom(queryItems:[URLQueryItem], key:String) -> String? {
return queryItems.filter({$0.name == key}).first?.value
}
Then your above code would look like:
if let queryItems = components?.queryItems {
// process the query items here...
let param1 = valueFrom(queryItems:queryItems, key:"item")
print("***************=> GOT IT ", param1)
}
You can use iMessageDataKit library. It makes setting and getting data really easy and straightforward like:
let message: MSMessage = MSMessage()
message.md.set(value: 7, forKey: "user_id")
message.md.set(value: "john", forKey: "username")
message.md.set(values: ["joy", "smile"], forKey: "tags")
print(message.md.integer(forKey: "user_id")!)
print(message.md.string(forKey: "username")!)
print(message.md.values(forKey: "tags")!)
(Disclaimer: I'm the author of iMessageDataKit)
I'm trying to use regex and range for the first time in Swift. I want to see if the letter the user enters into the textfield will match the word that they have to guess. If it does match the matching letter or letters will be displayed in a UILabel (similar to how you play hangman, if you guess the correct letter once and there are multiple occurrences of that letter, all occurrences will show). When a button is clicked the method below is called. It works fine when finding the matching letters, and inserting them at the right location, BUT when the UILabel is updated after the loop it only updates the label with the result of the second/final loop. How can I get a combination of the result from all the iterations of the loop? Any help would be appreciated. Thank you
func findLetter(displayedWord toSearchin: String, userInput toSearchFor: String) {
let ranges: [NSRange]
var labelUpdate = String()
do {
let regex = try NSRegularExpression(pattern: toSearchFor, options: [])
let displayedWord = toSearchin as NSString
let rangeOfSearch = NSMakeRange(0, displayedWord.length)
ranges = regex.matches(in: toSearchin, range: rangeOfSearch).map {$0.range}
let nsStringlabel = wordLabel.text as NSString?
for range in ranges {
labelUpdate = (nsStringlabel?.replacingCharacters(in: range, with: toSearchFor))!
print(labelUpdate)
//the word is lavenders, so this prints:
//___e_____
//______e__
// I want:
//___e__e__
}
DispatchQueue.main.async(execute: {
self.wordLabel.text = labelUpdate
})
}
catch {
ranges = []
}
}
As stated in a comment, you’re always updating the original nsStringlabel variable, thus always overriding the previous modification in the previous loop run.
I’d recommend you init labelUpdate with wordLabel.text as NSString? and completely remove nsStringlabel. This should solve your problem.
That being said, there are a lot of other problems that could be fixed in this function.
In particular, why use regexes? It’s expensive and not useful there.
Also, you’re dispatching before setting the label value, which is good, but not before retrieving the value… either a dispatch is needed or it is not, but it cannot be needed at one place and not at the other. If you call your function from the main thread (as a response to a user input for instance), you should be good and not need a dispatch.
Here what I would have done (should be safer and faster):
func updateLabel(withDestinationWord destinationWord: String, userInput: String) {
var labelText = wordLabel.text
var startIndex = labelText.characters.startIndex
while let r = destinationWord.range(of: userInput, options: .caseInsensitive, range: startIndex..<labelText.characters.endIndex) {
labelText.replaceSubrange(r, with: userInput)
startIndex = labelText.characters.index(after: r.lowerBound)
}
wordLabel.text = labelText
}
Be sure to have the same length for wordLabel.text and destinationWord!
Why in the world are Swift String operations so complex and tiresome to work with?
I have to iterate over a String in reverse but ignoring the first char. Now this could be done like following:
var firstTime = true
for i in textBefore.characters.reversed() {
if firstTime {
firstTime = false
} else {
if String(i).personalFunction() {
// something
} else {
// something else
}
}
}
But really I just want to do something like:
textBefore = textBefore.characters.reversed()
for i in 1...textBefore.characters.count {
if textBefore.get(i).personalFunction() {
// something
} else {
// something else
}
}
So why can't we get index as int. And why is textBefore.characters.reversed() not a String or simply have String have a reverse function. All these issues just makes it so frustrating to work with Strings in Swift and makes us do stupid stuff as converting a String to an array of chars :S or stuff like my proposed solution above... Also we can't make for loops in the old fashion... I simply need some Swift guru to point my brain in the right direction for this stuff.
string.characters is a collection of characters.
Use reversed() to access the elements in reverse order, anddropFirst() to skip the initial element of the reversed collection:
let string = "a🇨🇷b😈"
for ch in string.characters.reversed().dropFirst() {
print(ch)
// `ch` is a Character. Use `String(ch)` if you need a String.
}
Output:
b
🇨🇷
a
You can do something like your second one. After you enter the for, you can just get the index directly from the string. In Swift, a string is just an array of characters.
textBefore = String(textBefore.characters.reversed())
for i in 1...textBefore.characters.count {
if textBefore[i].personalFunction() {
// something
} else {
// something else
}
}
I'm having a problem with understand how I can work with substrings in Swift. Basically, I'm getting a JSON value that has a string with the following format:
Something
I'm trying to get rid of the HTML anchor tag with Swift so I'm left with Something. My thought was to find the index of every < and > in the string so then I could just do a substringWithRange and advance up to the right index.
My problem is that I can't figure out how to find the index. I've read that Swift doesn't support the index (unless you extend it.)
I don't want to add CPU cycles unnecessarily. So my question is, how do I find the indexes in a way that is not inefficient? Or, is there a better way of filtering out the tags?
Edit: Converted Andrew's first code sample to a function:
func formatTwitterSource(rawStr: String) -> String {
let unParsedString = rawStr
var midParseString = ""
var parsedString = ""
if let firstEndIndex = find(unParsedString, ">") {
midParseString = unParsedString[Range<String.Index>(start: firstEndIndex.successor(), end: unParsedString.endIndex)]
if let secondStartIndex = find(midParseString, "<") {
parsedString = midParseString[Range<String.Index>(start: midParseString.startIndex, end: secondStartIndex)]
}
}
return parsedString
}
Nothing too complicated. It takes in a String that has the tags in it. Then it uses Andrew's magic to parse everything out. I renamed the variables and made them clearer so you can see which variable does what in the process. Then in the end, it returns the parsed string.
You could do something like this, but it isn't pretty really. Obviously you would want to factor this into a function and possibly allow for various start/end tokens.
let testText = "Something"
if let firstEndIndex = find(testText, ">") {
let testText2 = testText[Range<String.Index>(start: firstEndIndex.successor(), end: testText.endIndex)]
if let secondStartIndex = find(testText2, "<") {
let testText3 = testText2[Range<String.Index>(start: testText2.startIndex, end: secondStartIndex)]
}
}
Edit
Working on this a little further and came up with something a little more idiomatic?
let startSplits = split(testText, { $0 == "<" })
let strippedValues = map(startSplits) { (s) -> String? in
if let endIndex = find(s, ">") {
return s[Range<String.Index>(start: endIndex.successor(), end: s.endIndex)]
}
return nil
}
let strings = map(filter(strippedValues, { $0 != "" })) { $0! }
It uses a little more functional style there at the end. Not sure I much enjoy the Swift style of map/filter compared to Haskell. But anyhow, the one potentially dangerous part is that forced unwrapping in the final map. If you can live with a result of [String?] then it isn't necessary.
Even though this question has been already answered, I am adding solution based on regex.
let pattern = "<.*>(.*)<.*>"
let src = "Something"
var error: NSError? = nil
var regex = NSRegularExpression(pattern: pattern, options: .DotMatchesLineSeparators, error: &error)
if let regex = regex {
var result = regex.stringByReplacingMatchesInString(src, options: nil, range: NSRange(location:0,
length:countElements(src)), withTemplate: "$1")
println(result)
}
I am trying to build an autocorrect system, so I need to be able to delete the last word typed and replace it with the correct one. My solution:
func autocorrect() {
hasWordReadyToCorrect = false
var wordProxy = self.textDocumentProxy as UITextDocumentProxy
var stringOfWords = wordProxy.documentContextBeforeInput
fullString = "Unset Value"
if stringOfWords != nil {
var words = stringOfWords.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceCharacterSet())
for word in words {
arrayOfWords += [word]
}
println("The last word of the array is \(arrayOfWords.last)")
for (mistake, word) in autocorrectList {
println("The mistake is \(mistake)")
if mistake == arrayOfWords.last {
fullString = word
hasWordReadyToCorrect = true
}
}
println("The corrected String is \(fullString)")
}
}
This method is called after each keystroke, and if the space is pressed, it corrects the word. My problem comes in when the string of text becomes longer than about 20 words. It takes a while for it to fill the array each time a character is pressed, and it starts to lag to a point of not being able to use it. Is there a more efficient and elegant Swift way of writing this function? I'd appreciate any help!
This doesn't answer the OP's "autocorrect" issue directly, but this is code is probably the easiest way to answer the question posed in the title:
Swift 3
let myString = "The dog jumped over a fence"
let myStringWithoutLastWord = myString.components(separatedBy: " ").dropLast().joined(separator: " ")
1.
One thing, iteration isn't necessary for this:
for word in words {
arrayOfWords += [word]
}
You can just do:
arrayOfWords += words
2.
Breaking the for loop will prevent iterating unnecessarily:
for (mistake, word) in autocorrectList {
println("The mistake is \(mistake)")
if mistake == arrayOfWords.last {
fullString = word
hasWordReadyToCorrect = true
break; // Add this to stop iterating through 'autocorrectList'
}
}
Or even better, forget the for-loop completely:
if let word = autocorrectList[arrayOfWords.last] {
fullString = word
hasWordReadyToCorrect = true
}
Ultimately what you're doing is seeing if the last word of the entered text matches any of the keys in the autocorrect list. You can just try to get the value directly using optional binding like this.
---
I'll let you know if I think of more.