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

stackoverflow.com/questions/24034043/…? stackoverflow.com/questions/39677330/… — Larme
– Larme, Commented Sep 5, 2017 at 8:03
You can cast it to NSString and check the range of matched string — Neil Galiaskarov
– Neil Galiaskarov, Commented Sep 5, 2017 at 8:04
@NeilGaliaskarov, and you shouldn't do this, Swift's String type has range method too. — user28434'mstep
– user28434'mstep, Commented Sep 5, 2017 at 8:09

vadian · Accepted Answer · 2017-09-05 08:32:00Z

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 5, 2017 at 8:32

answered Sep 5, 2017 at 8:25

vadian

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5 Comments

Rashmi Ranjan mallick Over a year ago

This is better approach

user28434'mstep Over a year ago

Also you can use URLComponents. *Well it won't help with finding stuff in path tho.

vadian Over a year ago

@user28434 Yes, but you can take advantage only if query is involved.

Evgeniy Kleban Over a year ago

@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 :)

vadian Over a year ago

A more universal solution is regular expression (regex) but you need to specify the range / boundaries of the substring to be extracted anyway.

axelspark · Accepted Answer · 2017-09-05 08:20:45Z

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

Vlad Khambir · Accepted Answer · 2017-09-05 08:21:28Z

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)

cwwise · Accepted Answer · 2017-09-05 08:29:05Z

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

nerowolfe · Accepted Answer · 2017-09-05 08:10:09Z

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)

PruitIgoe · Accepted Answer · 2018-06-26 10:45:02Z

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])

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