I have an array of strings like:

"Foo", "Foo1", "Foo$", "$Foo", "1Foo", "1$", "20$", "1$Foo", "12$$",  etc.

My required format is [Any number without dots][Must end with single $ symbol] (I mean, 1$ and 20$ from the above array)

I have tried like the below way, but it's not working.

func isValidItem(_ item: String) -> Bool {
   let pattern = #"^[0-9]$"#
   return (item.range(of: pattern, options: .regularExpression) != nil)
}

Can some one help me on this? Also, please share some great links to learn about the regex patterns if you have any.

Thank you

CodePudding user response：

You can use

func isValidItem(_ item: String) -> Bool {
   let pattern = #"^[0-9] \$\z"#
   return (item.range(of: pattern, options: .regularExpression) != nil)
}

let arr = ["Foo", "Foo1", "Foo$", "$Foo", "1Foo", "1$", "20$", "1$Foo", "12$$"]

print(arr.filter {isValidItem($0)})
// => ["1$", "20$"]

Here,

• ^ - matches start of a line
• [0-9] - one or more ASCII digits (note that Swift regex engine is ICU and \d matches any Unicode digits in this flavor, so [0-9] is safer if you need to only match digits from the 0-9 range)
• \$ - a $ char
• \z - the very end of string.

See the online regex demo ($ is used instead of \z since the demo is run against a single multiline string, hence the use of the m flag at regex101.com).