iOS Swift - 如何匹配“像”另一个字符串的字符串？ 即“http”就像“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?

Answer 1

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

Answer 2

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
        }
    }

Answer 3

a simple partial comparison can be achieved by using .contains

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