Swift - how to get specific substring from a given string

Question

I have string, that consist of one pre-defined string + random letters, like "https://www.facebook.com/" and "userId".

I have 3 predefined social host strings:

let vkPredefinedHost = "https://vk.com/"
let fbPredefinedHost = "https://www.facebook.com/"
let instPredefinedHost = "https://www.instagram.com/"

What i want is, extract social id, which is a string followed by that string (i don't know exactly which one i get).

So my question is:

1) How to check whether string contain one of this strings i pre-define

2) how to extract string followed by this strings

For example, i get "https://www.instagram.com/myUserId12345", and i want to get myUserId12345

https://stackoverflow.com/questions/24034043/how-do-i-check-if-a-string-contains-another-string-in-swift? https://stackoverflow.com/questions/39677330/how-does-string-substring-work-in-swift-3 — Larme, Sep 05 '17 at 08:03
You can cast it to NSString and check the range of matched string — Neil Galiaskarov, Sep 05 '17 at 08:04
@NeilGaliaskarov, and you shouldn't do this, Swift's String type has range method too. — user28434'mstep, Sep 05 '17 at 08:09

vadian · Accepted Answer · 2017-09-05T08:32:00.267

5

These strings are URL representations. Create an URL and compare the host and get the path
for example

let host = "www.instagram.com"

if let url = URL(string: "https://www.instagram.com/myUserId12345"),
    url.host == host {
    let userID = String(url.path.characters.dropFirst())
    print(userID)
}

It's necessary to drop the first character (a leading slash) from the path.

You can even write

let userID = url.lastPathComponent

if there are more path components and the requested information is the last one.

edited Sep 05 '17 at 08:32

answered Sep 05 '17 at 08:25

vadian

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1

This is better approach – Rashmi Ranjan mallick Sep 05 '17 at 08:29
Also you can use [URLComponents](https://developer.apple.com/documentation/foundation/urlcomponents). *Well it won't help with finding stuff in path tho. – user28434'mstep Sep 05 '17 at 09:01
1

@user28434 Yes, but you can take advantage only if `query` is involved. – vadian Sep 05 '17 at 09:34
@vadian thanks, it work in that specific case but i would prefer universal extension that we can apply for cases in which string is not url :) – Evgeniy Kleban Sep 05 '17 at 09:43
A more universal solution is regular expression (regex) but you need to specify the range / boundaries of the substring to be extracted anyway. – vadian Sep 05 '17 at 18:41

Vlad Khambir · Answer 2 · 2017-09-05T08:21:28.497

1

Try this extension:

let instPredefinedHost = "https://www.instagram.com/"
let text = "https://www.instagram.com/myUserId12345"

extension String {

    func getNeededText(for host: String) -> String {
        guard range(of: host) != nil else { return "" }
        return replacingOccurrences(of: host, with: "")
    }

}

text.getNeededText(for: instPredefinedHost)

edited Sep 05 '17 at 08:21

answered Sep 05 '17 at 08:17

Vlad Khambir

4,313
1
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score 1 · Answer 3 · answered Sep 05 '17 at 08:20

You can use the built in RegEx in Swift:

let hostString = "Put your string here"

let pattern = "https:\/\/\w+.com\/(\w)" // any https://___.com/ prefix

let regex = try! NSRegularExpression(pattern: pat, options: [])

let match = regex.matchesInString(hostString, options: [], range: NSRange(location: 0, length: hostString.characters.count))

print(match[0]) // your social id

score 1 · Answer 4 · answered Sep 05 '17 at 08:29

You can use hasPrefix or contains to do. but I think hasPrefix may be best.

let instPredefinedHost = "https://www.instagram.com/" let userUrlString = "https://www.instagram.com/myUserId12345" let result = userUrlString.hasPrefix(instPredefinedHost) let result = userUrlString.contains(instPredefinedHost)
can use URL or separated String

let instPredefinedHost = "https://www.instagram.com/" let userUrl = URL(string: userUrlString) let socialId = userUrl?.lastPathComponent let socialId = userUrlString.components(separatedBy: instPredefinedHost).last

score 0 · Answer 5 · answered Sep 05 '17 at 08:10

You can use such type of extension:

extension String{
    func exclude(_ find:String) -> String {
        return replacingOccurrences(of: find, with: "", options: .caseInsensitive, range: nil)
    }
    func replaceAll(_ find:String, with:String) -> String {
        return replacingOccurrences(of: find, with: with, options: .caseInsensitive, range: nil)
    }
}

}

And use simply

let myaccount = fullString.exclude(find : instPredefinedHost)

score 0 · Answer 6 · answered Jun 26 '18 at 10:45

Since you are trying to parse URLs why reinvent the wheel when Apple has already done the heavy lifting for you with URLComponents?

let myURLComps = URLComponents(string: "https://www.instagram.com/myUserId12345?test=testvar&test2=teststatic")

if let theseComps = myURLComps {

    let thisHost = theseComps.host
    let thisScheme = theseComps.scheme
    let thisPath = theseComps.path
    let thisParams = theseComps.queryItems

    print("\(thisScheme)\n\(thisHost)\n\(thisPath)\n\(thisParams)")
}

prints:

Optional("https")
Optional("www.instagram.com")
/myUserId12345
Optional([test=testvar, test2=teststatic])

Swift - how to get specific substring from a given string

6 Answers6