How do you make a letter count as another when finding a substring in Swift? For example, I have a string:
I like to eat apples
But I want to be able to make it where all instances of 'p' could be written as 'b'.
If the user searches "abbles", it should still return the substring "apples" from the quote. I have this issue because I want whenever a user searches
اكل
But the quote contains
أكل
it would return that value. I tried fullString.range(of: string, options: [.diacriticInsensitive, .caseInsensitive] but this does not fix it since the "ء" are not diacritics, so أ إ ا all behave differently when they should all be the same. Users only use ا. How do I make it count for أ and إ without replacing all instances of them with ا?
You could add a small String extension that uses simple regular expressions (as matt suggested in the comments) to do the actual matching. Like so:
extension String {
func contains(substring: String, disregarding: [String]) -> Bool {
var escapedPattern = NSRegularExpression.escapedPattern(for: substring)
for string in disregarding {
let replacement = String(repeating: ".", count: string.count)
escapedPattern = escapedPattern.replacingOccurrences(of: string, with: replacement)
}
let regEx = ".*" + escapedPattern + ".*"
return self.range(of: regEx,
options: .regularExpression) != nil
}
}
Example output:
"I like apples".contains(substring: "apples", disregarding: ["p"]) //true
"I like abbles".contains(substring: "apples", disregarding: ["p"]) //true
"I like oranges".contains(substring: "apples", disregarding: ["p"]) //false
Related
First let me point out... I want to split a String or Substring with any character that is not an alphabet, a number, # or #. That means, I want to split with whitespaces(spaces & line breaks) and special characters or symbols excluding # and #
In Android Java, I am able to achieve this with:
String[] textArr = text.split("[^\\w_##]");
Now, I want to do the same in Swift. I added an extension to String and Substring classes
extension String {}
extension Substring {}
In both extensions, I added a method that returns an array of Substring
func splitWithRegex(by regexStr: String) -> [Substring] {
//let string = self (for String extension) | String(self) (for Substring extension)
let regex = try! NSRegularExpression(pattern: regexStr)
let range = NSRange(string.startIndex..., in: string)
return regex.matches(in: string, options: .anchored, range: range)
.map { match -> Substring in
let range = Range(match.range(at: 1), in: string)!
return string[range]
}
}
And when I tried to use it, (Only tested with a Substring, but I also think String will give me the same result)
let textArray = substring.splitWithRegex(by: "[^\\w_##]")
print("substring: \(substring)")
print("textArray: \(textArray)")
This is the out put:
substring: This,is a #random #text written for debugging
textArray: []
Please can Someone help me. I don't know if the problem if from my regex [^\\w_##] or from splitWithRegex method
The main reason why the code doesn't work is range(at: 1) which returns the content of the first captured group, but the pattern does not capture anything.
With just range the regex returns the ranges of the found matches, but I suppose you want the characters between.
To accomplish that you need a dynamic index starting at the first character. In the map closure return the string from the current index to the lowerBound of the found range and set the index to its upperBound. Finally you have to add manually the string from the upperBound of the last match to the end.
The Substring type is a helper type for slicing strings. It should not be used beyond a temporary scope.
extension String {
func splitWithRegex(by regexStr: String) -> [String] {
guard let regex = try? NSRegularExpression(pattern: regexStr) else { return [] }
let range = NSRange(startIndex..., in: self)
var index = startIndex
var array = regex.matches(in: self, range: range)
.map { match -> String in
let range = Range(match.range, in: self)!
let result = self[index..<range.lowerBound]
index = range.upperBound
return String(result)
}
array.append(String(self[index...]))
return array
}
}
let text = "This,is a #random #text written for debugging"
let textArray = text.splitWithRegex(by: "[^\\w_##]")
print(textArray) // ["This", "is", "a", "#random", "#text", "written", "for", "debugging"]
However in macOS 13 and iOS 16 there is a new API quite similar to the java API
let text = "This,is a #random #text written for debugging"
let textArray = Array(text.split(separator: /[^\w_##]/))
print(textArray)
The forward slashes indicate a regex literal
I have an array of strings like:
"Foo", "Foo1", "Foo$", "$Foo", "1Foo", "1$", "20$", "1$Foo", "12$$", etc.
My required format is [Any number without dots][Must end with single $ symbol] (I mean, 1$ and 20$ from the above array)
I have tried like the below way, but it's not working.
func isValidItem(_ item: String) -> Bool {
let pattern = #"^[0-9]$"#
return (item.range(of: pattern, options: .regularExpression) != nil)
}
Can some one help me on this? Also, please share some great links to learn about the regex patterns if you have any.
Thank you
You can use
func isValidItem(_ item: String) -> Bool {
let pattern = #"^[0-9]+\$\z"#
return (item.range(of: pattern, options: .regularExpression) != nil)
}
let arr = ["Foo", "Foo1", "Foo$", "$Foo", "1Foo", "1$", "20$", "1$Foo", "12$$"]
print(arr.filter {isValidItem($0)})
// => ["1$", "20$"]
Here,
^ - matches start of a line
[0-9]+ - one or more ASCII digits (note that Swift regex engine is ICU and \d matches any Unicode digits in this flavor, so [0-9] is safer if you need to only match digits from the 0-9 range)
\$ - a $ char
\z - the very end of string.
See the online regex demo ($ is used instead of \z since the demo is run against a single multiline string, hence the use of the m flag at regex101.com).
I have a string "A very nice beach" and I want to be able to see if it contains any words of the substring within the array of wordGroups.
let string = "A very nice beach"
let wordGroups = [
"beach",
"waterfront",
"with a water view",
"near ocean",
"close to water"
]
First solution is for exactly matching the word or phrase in wordGroups using regex
var isMatch = false
for word in wordGroups {
let regex = "\\b\(word)\\b"
if string.range(of: regex, options: .regularExpression) != nil {
isMatch = true
break
}
}
As suggested in the comments the above loop can be replace with a shorter contains version
let isMatch = wordGroups.contains {
string.range(of: "\\b\($0)\\b", options: .regularExpression) != nil
}
Second solution is for simply text if string contains the any of the strings in the array
let isMatch2 = wordGroups.contains(where: string.contains)
So for "A very nice beach" both returns true but for "Some very nice beaches" only the second one returns true
Wasn't too sure how to interpret "to see if it contains any words of the substring within the array of wordGroups", but this solution checks to see if any words of your input string are contained in any substring of your word groups.
func containsWord(str: String, wordGroups: [String]) -> Bool {
// Get all the words from your input string
let words = str.split(separator: " ")
for group in wordGroups {
// Put all the words in the group into set to improve lookup time
let set = Set(group.split(separator: " "))
for word in words {
if set.contains(word) {
return true
}
}
}
return false
}
I'm very, very new to Swift and admittedly struggling with some of its constructs. I have to work with a text file and do many manipulations - here's an example to illustrate the point:
let's say I have a text like this (multi line)
Mary had a little lamb
#name: a name
#summary: a paragraph of text
{{something}}
a whole bunch of multi-line text
x----------------x
I want to be able to do simple things like find the location of #name, then split it to get the name and so on. I've done this in javascript and it was pretty simple with the use of substr and the regex matches.
In swift, which is supposed to be swift and easy and what not, I'm finding this exceedingly confusing.
Can someone help with how one might do
Find the location of the start of a substring
Extract all text between from the end of a substring to the end of text
Sorry if this is trivial - but the Apple documentation feels very complicated, and lots of examples are years old. I can't also seem to find easy application of regex.
You can use string range(of: String) method to find the range of your string, get its upperBound and search for the end of the line from that position of the string:
Playground testing:
let sentence = """
Mary had a little lamb
#name: a name
#summary: a paragraph of text
{{something}}
a whole bunch of multi-line text
"""
if let start = sentence.range(of: "#name:")?.upperBound,
let end = sentence[start...].range(of: "\n")?.lowerBound {
let substring = sentence[start..<end]
print("name:", substring)
}
If you need to get the string from there to the end of the string you can use PartialRangeFrom:
if let start = sentence.range(of: "#summary:")?.upperBound {
let substring = sentence[start...]
print("summary:", substring)
}
If you find yourself using that a lot you can extend StringProtocol and create your own method:
extension StringProtocol {
func substring<S:StringProtocol,T:StringProtocol>(between start: S, and end: T, options: String.CompareOptions = []) -> SubSequence? {
guard
let lower = range(of: start, options: options)?.upperBound,
let upper = self[lower...].range(of: end, options: options)?.lowerBound
else { return nil }
return self[lower..<upper]
}
func substring<S:StringProtocol>(after string: S, options: String.CompareOptions = []) -> SubSequence? {
guard
let lower = range(of: string, options: options)?.upperBound else { return nil }
return self[lower...]
}
}
Usage:
let name = sentence.substring(between: "#name:", and: "\n") // " a name"
let sumary = sentence.substring(after: "#summary:") // " a paragraph of text\n\n{{something}}\n\na whole bunch of multi-line text"
You can use regular expressions as well:
let name = sentence.substring(between: "#\\w+:", and: "\\n", options: .regularExpression) // " a name"
You can do this with range() and distance():
let str = "Example string"
let range = str.range(of: "amp")!
print(str.distance(from: str.startIndex, to: range.lowerBound)) // 2
let lastStr = str[range.upperBound...]
print(lastStr) // "le string"
I'm bit confused by NSRegularExpression in swift, can any one help me?
task:1 given ("name","john","name of john")
then I should get ["name","john","name of john"]. Here I should avoid the brackets.
task:2 given ("name"," john","name of john")
then I should get ["name","john","name of john"]. Here I should avoid the brackets and extra spaces and finally get array of strings.
task:3 given key = value // comment
then I should get ["key","value","comment"]. Here I should get only strings in the line by avoiding = and //
I have tried below code for task 1 but not passed.
let string = "(name,john,string for user name)"
let pattern = "(?:\\w.*)"
do {
let regex = try NSRegularExpression(pattern: pattern, options: .caseInsensitive)
let matches = regex.matches(in: string, options: [], range: NSRange(location: 0, length: string.utf16.count))
for match in matches {
if let range = Range(match.range, in: string) {
let name = string[range]
print(name)
}
}
} catch {
print("Regex was bad!")
}
Thanks in advance.
RegEx in Swift
These posts might help you to explore regular expressions in swift:
Does a string match a pattern?
Swift extract regex matches
How can I use String slicing subscripts in Swift 4?
How to use regex with Swift?
Swift 3 - How do I extract captured groups in regular expressions?
How to group search regular expressions using swift?
Task 1 & 2
This expression might help you to match your desired outputs for both Task 1 and 2:
"(\s+)?([a-z\s]+?)(\s+)?"
Based on Rob's advice, you could much reduce the boundaries, such as the char list [a-z\s]. For example, here, we can also use:
"(\s+)?(.*?)(\s+)?"
or
"(\s+)?(.+?)(\s+)?"
to simply pass everything in between two " and/or space.
RegEx
If this wasn't your desired expression, you can modify/change your expressions in regex101.com.
RegEx Circuit
You can also visualize your expressions in jex.im:
JavaScript Demo
const regex = /"(\s+)?([a-z\s]+?)(\s+)?"/gm;
const str = `"name","john","name of john"
"name"," john","name of john"
" name "," john","name of john "
" name "," john"," name of john "`;
const subst = `\n$2`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Task 3
This expression might help you to design an expression for the third task:
(.*?)([a-z\s]+)(.*?)
const regex = /(.*?)([a-z\s]+)(.*?)/gm;
const str = `key = value // comment
key = value with some text // comment`;
const subst = `$2,`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Separate the string by non alpha numeric characters except white spaces. Then trim the elements with white spaces.
extension String {
func words() -> [String] {
return self.components(separatedBy: CharacterSet.alphanumerics.inverted.subtracting(.whitespaces))
.filter({ !$0.isEmpty })
.map({ $0.trimmingCharacters(in: .whitespaces) })
}
}
let string1 = "(name,john,string for user name)"
let string2 = "(name, john,name of john)"
let string3 = "key = value // comment"
print(string1.words())//["name", "john", "string for user name"]
print(string2.words())//["name", "john", "name of john"]
print(string3.words())//["key", "value", "comment"]
Here I have done with after understanding all of above comments.
let text = """
Capturing and non-capturing groups are somewhat advanced topics. You’ll encounter examples of capturing and non-capturing groups later on in the tutorial
"""
extension String {
func rex (_ expr : String)->[String] {
return try! NSRegularExpression(pattern: expr, options: [.caseInsensitive])
.matches(in: self, options: [], range: NSRange(location: 0, length: self.count))
.map {
String(self[Range($0.range, in: self)!])
}
}
}
let r = text.rex("(?:\\w+-\\w+)") // pass any rex
A single pattern, works for test:1...3, in Swift.
let string =
//"(name,john,string for user name)" //test:1
//#"("name"," john","name of john")"# //test:2
"key = value // comment" //test:3
let pattern = #"(?:\w+)(?:\s+\w+)*"# //Swift 5+ only
//let pattern = "(?:\\w+)(?:\\s+\\w+)*"
do {
let regex = try NSRegularExpression(pattern: pattern)
let matches = regex.matches(in: string, range: NSRange(0..<string.utf16.count))
let matchingWords = matches.map {
String(string[Range($0.range, in: string)!])
}
print(matchingWords) //(test:3)->["key", "value", "comment"]
} catch {
print("Regex was bad!")
}
Let’s consider:
let string = "(name,José,name is José)"
I’d suggest a regex that looks for strings where:
It’s the substring either after the ( at the start of the full string or after a comma, i.e., look behind assertion of (?<=^\(|,);
It’s the substring that does not contain , within it, i.e., [^,]+?;
It’s the substring that is terminated by either a comma or ) at the end of the full string, i.e., look ahead assertion of (?=,|\)$), and
If you want to have it skip white space before and after the substrings, throw in the \s*+, too.
Thus:
let pattern = #"(?<=^\(|,)\s*+([^,]+?)\s*+(?=,|\)$)"#
let regex = try! NSRegularExpression(pattern: pattern)
regex.enumerateMatches(in: string, range: NSRange(string.startIndex..., in: string)) { match, _, _ in
if let nsRange = match?.range(at: 1), let range = Range(nsRange, in: string) {
let substring = String(string[range])
// do something with `substring` here
}
}
Note, I’m using the Swift 5 extended string delimiters (starting with #" and ending with "#) so that I don’t have to escape my backslashes within the string. If you’re using Swift 4 or earlier, you’ll want to escape those back slashes:
let pattern = "(?<=^\\(|,)\\s*+([^,]+?)\\s*+(?=,|\\)$)"