iOS Swift - How to match a string that is "like" another string? i.e. "http" is like "http://"

Question

I created a URL Validation function that validates for URL as text is entered by a user into a text field.

However, in an effort to save performance and memory, I want to ignore entries that may contain common URL prefixes:

(i.e. http://, http://www, www, etc)

With that said, I want to be able to "smartly" ignore text that may MATCH one of these URL prefixes:

["http://www", "https://www", "www"]
i.e. If a user has typed "htt", it should be ignored since it is a substring of "http://www" or "https://www"

What is the best way to check if a string may match provided prefixes but not necessarily are equal?

Does this help? stackoverflow.com/questions/25071444/regex-in-swift — Mike Taverne
– Mike Taverne, Commented Nov 18, 2014 at 2:48

akshay · Accepted Answer · 2014-11-18 00:49:36Z

2

From the Swift Programming Language Guide, you can use the hasPrefix method.

Example:

if userString.hasPrefix("http") {
    // do something with userString
}

Source: Swift Programming Language Guide

answered Nov 18, 2014 at 0:49

akshay

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1 Comment

JimmyJammed Over a year ago

That only matches the whole string. Doesn't match partial strings. I figured it out, see below answer.

JimmyJammed · Accepted Answer · 2014-11-18 22:30:12Z

0

Ok, figured it out. Had to use 'rangeOfString' function and check if user's text was in my control text.

Code:

    let prefixes = ["http://www.", "https://www.", "www."]
    for prefix in prefixes
    {
        if ((prefix.rangeOfString(urlString!, options: NSStringCompareOptions.CaseInsensitiveSearch, range: nil, locale: nil)) != nil){
            completion(success: false, urlString: nil, error: "Url String was prefix only")
            return
        }
    }

answered Nov 18, 2014 at 22:30

JimmyJammed

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Comments

Frostmourne · Accepted Answer · 2020-04-24 04:45:10Z

0

a simple partial comparison can be achieved by using .contains

let string = "hello Swift"
if string.contains("Swift") {
    print("exists")
}

answered Apr 24, 2020 at 4:45

Frostmourne

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