Swift replace occurrence of string with condition

Question

I have string like below

I am a strongPerson

I want to covert this string like this

I am a weakPerson

When I try below code

let old = "<p><strong>I am a strongPerson</strong></p>"
let new = old.replacingOccurrences(of: "strong", with: "weak")
print("\(new)")

I am getting output like

<weak>I am a weakPerson</weak>

But I need output like this

I am a weakPerson

My Condition here is

1.It has to replace only if word does not contain these HTML Tags like "<>".

Help me to get it. Thanks in advance.

@Sh_Khan Can you please kindly help me to write Regular Expression? — Mani murugan, Jun 20 '19 at 16:40

score 3 · Accepted Answer · answered Jun 20 '19 at 16:45

3

You can use a regular expression to avoid the word being in a tag:

let old = "strong <p><strong>I am a strong person</strong></p> strong"
let new = old.replacingOccurrences(of: "strong(?!>)", with: "weak", options: .regularExpression, range: nil)
print(new)

I added some extra uses of the word "strong" to test edge cases.

The trick is the use of (?!>) which basically means to ignore any match that has a > at the end of it. Look at the documentation for NSRegularExpression and find the documentation for the "negative look-ahead assertion".

Output:

weak I am a weak person weak

answered Jun 20 '19 at 16:45

rmaddy

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2

I recommend that you also use a negative look-behind to avoid matching `"strong>"`, so the regular expression would then be `"(?<!<|<\/)strong(?!>)"`. A link to explain this is here: regexr.com/4g5o4 – Sam Jun 20 '19 at 16:51
1

@Sam I was assuming you would never find `strong>` in the string because the `>` would be entered as `>`. – rmaddy Jun 20 '19 at 16:52
@Sam It shows error for this string "\" , Invalid escape sequence in literal – Mani murugan Jun 20 '19 at 16:56
1

In a Swift string you would need `"(?<!<|<\\/)string(?!>)"`. Note the double backslash. – rmaddy Jun 20 '19 at 16:57
1

@Manimurugan Exactly – Sam Jun 20 '19 at 16:58

Abdulrahman Falyoun · Answer 2 · 2019-06-20T17:03:24.313

1

Try the following:

let myString = "<p><strong>I am a strongPerson</strong></p>"
if let regex = try? NSRegularExpression(pattern: "strong(?!>)") {

 let modString = regex.stringByReplacingMatches(in: myString, options: [], range: NSRange(location: 0, length:  myString.count), withTemplate: "weak")
  print(modString)
}

edited Jun 20 '19 at 17:03

answered Jun 20 '19 at 16:47

Abdulrahman Falyoun

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Why case insensitive? – rmaddy Jun 20 '19 at 16:53
In case of ``
I am a StrongPerson
``, As well as i have it in one of my file so he can omit it – Abdulrahman Falyoun Jun 20 '19 at 17:00
1

But then `StrongPerson` becomes `weakPerson` and not `WeakPerson`. That may or may not be what the OP wants. – rmaddy Jun 20 '19 at 17:01
Thanks for your note, I'll omit it – Abdulrahman Falyoun Jun 20 '19 at 17:02

Swift replace occurrence of string with condition

2 Answers2