Swift 2 NSRegularExpression - regex

Question

Eventually I want to be able to input a string like "\mycard{front1}{back1} \mycard{front2}{back2} \mycard{front3}{back3}" and return the front and back of each card.
I found this website on NSRegularExpression, but I'm having a hard time adjusting it to my problem.
Here is what I have so far.
import Foundation
func rangeFromNSRange(nsRange: NSRange, forString str: String) -> Range<String.Index>? {
let fromUTF16 = str.utf16.startIndex.advancedBy(nsRange.location, limit: str.utf16.endIndex)
let toUTF16 = fromUTF16.advancedBy(nsRange.length, limit: str.utf16.endIndex)
if let from = String.Index(fromUTF16, within: str), let to = String.Index(toUTF16, within: str) {
return from ..< to
}
return nil
}
do {
// let input = "My name is Taylor Swift"
// let regex = try NSRegularExpression(pattern: "My name is (.*)", options: NSRegularExpressionOptions.CaseInsensitive)
let input = "mycard{front}{back}"
let regex = try NSRegularExpression(pattern: "mycard{(.*)}{(.*)}", options: NSRegularExpressionOptions.CaseInsensitive)
let matches = regex.matchesInString(input, options: [], range: NSMakeRange(0, input.characters.count))
if let match = matches.first {
let range = match.rangeAtIndex(1)
if let swiftRange = rangeFromNSRange(range, forString: input) {
let name = input.substringWithRange(swiftRange)
}
}
} catch {
// regex was bad!
}

Answer 1

As stated in my comment you need to escape the { and }. That results in the following regex: mycard\\{(.*)\\}\\{(.*)\\}.
You then might want to change your match logic a little bit to output the expected results:
if let match = matches.first {
for i in 1..<match.numberOfRanges {
let range = match.rangeAtIndex(i)
if let swiftRange = rangeFromNSRange(range, forString: input) {
let name = input.substringWithRange(swiftRange)
print(name)
}
}
}
Which outputs
front
back
If you want to match multiple cards use the following regex:
mycard\\{([^{]*)\\}\\{([^{]*)\\}
Then iterate over the matches
for match in matches {
for i in 1..<match.numberOfRanges {
let range = match.rangeAtIndex(i)
if let swiftRange = rangeFromNSRange(range, forString: input) {
let name = input.substringWithRange(swiftRange)
print(name)
}
}
}
For the input mycard{front}{back} mycard{front1}{back1} the output correctly is
front
back
front1
back1

Answer 2

I gave up on regex. I just don't think it will do the trick here. I came up with another solution.
import Foundation
extension String {
subscript (r: Int) -> Character? {
var cur = 0
for char in self.characters {
if cur == r {
return char
}
cur += 1
}
return nil
}
subscript (r: Range<Int>) -> String {
return substringWithRange(Range(start: startIndex.advancedBy(r.startIndex), end: startIndex.advancedBy(r.endIndex)))
}
func parseBrackets () -> [String]? {
var list: [String] = []
var level = 0
var start = 0
for var i=0; i < self.characters.count - 1; i++ {
if self[i] == "{" {
level += 1
if level == 1 {
start = i + 1
}
} else if self[i] == "}" {
if level == 1 {
list.append(self[start..<i])
}
level -= 1
}
}
if list.count > 0 {
return list
} else {
return nil
}
}
}
let testString = "mycard{f{}ront}{termins{x}{n}} mycard{front1}{back1} mycard{front2}{back2}"
let list = testString.parseBrackets()
for a in list! {
print(a)
}
Which gives the desired output
f{}ront
termins{x}{n}
front1
back1
front2