I need to count the number of leading tabs in a Swift string. I know there are fairly simple solutions (e.g. looping over the string until a non-tab character is encountered) but I am looking for a more elegant solution.
I have attempted to use a regex such as ^\\t* along with the .numberOfMatches method but this detects all the tab characters as one match. For example, if the string has three leading tabs then that method just returns 1. Is there a way to write a regex that treats each individual tab character as a single match?
Also open to other ways of approaching this without using a regex.
Here is a non-regex solution
let count = someString.prefix(while: {$0 == "\t"}).count
You may use
\G\t
See the regex demo.
Here,
\G - matches a string start position or end of the previous match position, and
\t - matches a single tab.
Swift test:
let string = "\t\t123"
let regex = try! NSRegularExpression(pattern: "\\G\t", options: [])
let numberOfOccurrences = regex.numberOfMatches(in: string, range: NSRange(string.startIndex..., in: string))
print(numberOfOccurrences) // => 2
Related
i am having problems using replacingOccurrences to replace a word after some specific keywords inside a textview in swift 5 and Xcode 12.
For example:
My textview will have the following string "NAME\JOHN PHONE\555444333"
"NAME" and "PHONE" will be unique so anytime i change the proper field i want to change the name or phone inside this textview.
let's for example change JOHN for CLOE with the code
txtOther.text = txtOther.text.replacingOccurrences(of: "NAME(.*?)\\s", with: "NAME\\\(new_value) ", options: .regularExpression)
print (string)
output: "NAMECLOE " instead of "NAME\CLOE "
I can't get the backslash to get print according to the regular expression.
Or maybe change the regex expression just to change JOHN for CLOE after "NAME"
Thanks!!!
Ariel
You can solve this by using a raw string for your regular expresion, that is a string surrounded with #
let pattern = #"(NAME\\)(.*)\s"#
Note that name and the \ is in a separate group that can be referenced when replacing
let output = string.replacingOccurrences(of: pattern, with: "$1\(new_value) ", options: .regularExpression)
Use
"NAME\\JOHN PHONE\\555444333".replacingOccurrences(
of: #"NAME\\(\S+)"#,
with: "NAME\\\\\(new_value)",
options: .regularExpression
)
Double backslashes in the replacement, backslash is a special metacharacter inside a replacement.
\S+ matches one or more characters different from whitespace, this is shorter and more efficient than .*?\s, and you do not have to worry about how to put back the whitespace.
I'm attempting to sanitize a string in Swift using a single StringTransform.
I'm using this example string: "Mom's \t Famous \"Ćevapčići\"!"
And the expected result is: "moms-famous-cevapcici"
So far, I've been able to achieve this using a combination of StringTransform and NSRegularExpression:
"Mom's \t Famous \"Ćevapčići\"!"
.applyingTransform(StringTransform("Latin-ASCII; Lower; [:Punctuation:] Remove;"))?
// produces: Optional("moms famous\tcevapcici")
.replacingMatches(
by: try! NSRegularExpression(pattern: "[^a-z0-9]+", options: []),
withTemplate: "-"
)
// produces: Optional("moms-famous-cevapcici")
Is there a way to do this using only StringTransform?
So far, I've only figured out how to remove certain characters, but not replace them. Eg.:
StringTransform("Latin-ASCII; Lower; [:Punctuation:] Remove; [^a-z0-9] Remove;")
The above transform produces "momsfamouscevapcici".
I'd also like to avoid this result: moms---famous-cevapcici. Ideally, this transform could replace several consecutive characters with one dash.
This is my string
"I made this wonderful pic last #chRistmas... #instagram #nofilter #snow #fun"
and I would like to get hashtag that contains # at the beginning and end without space. My expected result is:
$fun
This is what I have so far for regex search:
#[a-z0-9]+
but it give me all the hashtags not the one that I want. Thank you for your help!
Using #[a-zA-Z0-9]*$ instead of your current regex
It seems you need to match a hashtag at the end of the string, or the last hashtag in the string. So, there are several ways solve the issue.
Matching the last hashtag in the string
let str = "I made this wonderful pic last #chRistmas... #instagram #nofilter #snow #fun"
let regex = "#[[:alnum:]]++(?!.*#[[:alnum:]])"
if let range = str.range(of: regex, options: .regularExpression) {
let text: String = String(str[range])
print(text)
}
Details
# - a hash symbol
[[:alnum:]]++ - 1 or more alphanumeric chars
(?!.*#[[:alnum:]]) - no # + 1+ alphanumeric chars after any 0+ chars other than line break chars immediately to the right of the current location.
Matching a hashtag at the end of the string
Same code but with the following regexps:
let regex = "#[[:alnum:]]+$"
or
let regex = "#[[:alnum:]]+\\z"
Note that \z matches the very end of string, if there is a newline char between the hashtag and the end of string, there won't be any match (in case of $, there will be a match).
Note on the regex
If a hashtag should only start with a letter, it is a better idea to use
#[[:alpha:]][[:alnum:]]*
where [[:alpha:]] matches any letter and [[:alnum:]]* matches 0+ letters or/and digits.
Note that in ICU regex patterns, you may write [[:alnum:]] as [:alnum:].
You can use:
(^#[a-z0-9]+|#[a-z0-9]+$)
Test it online
I'm trying to remove the last numbers of an IP address string in Swift so I can loop through IP addresses. For instance if my variable = 192.168.1.123, I would like to trim the string to equal 192.169.1.
I'm not sure how to do this since some IP addresses will end in 1, 2 or 3 digits. I couldn't figure out how to trim back to a certain character.
I have a solution (In your case only). You can try it
let str = "192.168.1.123"
var arr = str.components(separatedBy: ".")
arr.removeLast()
let newstr = arr.joined(separator: ".") + "."
You can find the range of the last .:
let ip = "192.168.1.123"
let lastdot = ip.range(of: ".", options: .backwards)!
let base = ip[...lastdot.lowerBound]
This code assumes there is at least one . in the string. If not it will crash. That is easily fixed with proper use of if let.
base will be a Substring so depending on what you do next, you may need to wrap that as:
let base = String(ip[...lastdot.lowerBound])
Whether explicitly converting to String depends on whether subsequent methods require String or StringProtocol. Converting to String copies over the storage again, which is costly and unnecessary for many operations, but may be required in some cases.
Having a string like this:
let str = "In 1273, however, they lost their son in an accident;[2] the young Theobald was dropped by his nurse over the castle battlements.[3]"
I'm looking for a solution of removing all appearances of square brackets and anything that between it.
I was trying using a String's method: replacingOccurrences(of:with:), but it requires the exact substring it needs to be removed, so it doesn't work for me.
You can use:
let updated = str.replacingOccurrences(of: "\\[[^\\]]+\\]", with: "", options: .regularExpression)
The regular expression (without the required escapes needed in a Swift string is:
\[[^\]+]\]
The \[ and \] look for the characters [ and ]. They have a backslash to remove the normal special meaning of those characters in a regular expression.
The [^]] means to match any character except the ] character. The + means match 1 or more.
You can create a while loop to get the lowerBound of the range of the first string and the upperBound of the range of the second string and create a range from that. Next just remove the subrange of your string and set the new startIndex for the search.
var str = "In 1273, however, they lost their son in an accident;[2] the young Theobald was dropped by his nurse over the castle battlements.[3]"
var start = str.startIndex
while let from = str.range(of: "[", range: start..<str.endIndex)?.lowerBound,
let to = str.range(of: "]", range: from..<str.endIndex)?.upperBound,
from != to {
str.removeSubrange(from..<to)
start = from
}
print(str) // "In 1273, however, they lost their son in an accident; the young Theobald was dropped by his nurse over the castle battlements."