如何在 Swift 语言中比较两个字符串而忽略大小写？

Question

How can we compare two strings in swift ignoring case ? for eg :

var a = "Cash"
var b = "cash"

Is there any method that will return true if we compare var a & var b

Answer 1

Try this :

For older swift:

var a : String = "Cash"
var b : String = "cash"

if(a.caseInsensitiveCompare(b) == NSComparisonResult.OrderedSame){
    println("voila")
}

---

Swift 3+

var a : String = "Cash"
var b : String = "cash"

if(a.caseInsensitiveCompare(b) == .orderedSame){
    print("voila")
}

Answer 2

Use caseInsensitiveCompare method:

let a = "Cash"
let b = "cash"
let c = a.caseInsensitiveCompare(b) == .orderedSame
print(c) // "true"

ComparisonResult tells you which word comes earlier than the other in lexicographic order (ie which one comes closer to the front of a dictionary). .orderedSame means the strings would end up in the same spot in the dictionary

Answer 3

if a.lowercaseString == b.lowercaseString {
    //Strings match
}

Answer 4

Try this:

var a = "Cash"
var b = "cash"
let result: NSComparisonResult = a.compare(b, options: NSStringCompareOptions.CaseInsensitiveSearch, range: nil, locale: nil)

// You can also ignore last two parameters(thanks 0x7fffffff)
//let result: NSComparisonResult = a.compare(b, options: NSStringCompareOptions.CaseInsensitiveSearch)

result is type of NSComparisonResult enum:

enum NSComparisonResult : Int {

    case OrderedAscending
    case OrderedSame
    case OrderedDescending
}

So you can use if statement:

if result == .OrderedSame {
    println("equal")
} else {
    println("not equal")
}

Answer 5

CORRECT WAY:

let a: String = "Cash"
let b: String = "cash"

if a.caseInsensitiveCompare(b) == .orderedSame {
    //Strings match 
}

Please note: ComparisonResult.orderedSame can also be written as .orderedSame in shorthand.

OTHER WAYS:

a.

if a.lowercased() == b.lowercased() {
    //Strings match 
}

b.

if a.uppercased() == b.uppercased() {
    //Strings match 
}

c.

if a.capitalized() == b.capitalized() {
    //Strings match 
}

Answer 6

localizedCaseInsensitiveContains : Returns whether the receiver contains a given string by performing a case-insensitive, locale-aware search

if a.localizedCaseInsensitiveContains(b) {
    //returns true if a contains b (case insensitive)
}

Edited :

caseInsensitiveCompare : Returns the result of invoking compare(_:options:) with NSCaseInsensitiveSearch as the only option.

if a.caseInsensitiveCompare(b) == .orderedSame {
    //returns true if a equals b (case insensitive)
}

Answer 7

Could just roll your own:

func equalIgnoringCase(a:String, b:String) -> Bool {
    return a.lowercaseString == b.lowercaseString
}

Answer 8

Phone numbers comparison example; using swift 4.2

var selectPhone = [String]()

if selectPhone.index(where: {$0.caseInsensitiveCompare(contactsList[indexPath.row].phone!) == .orderedSame}) != nil {
    print("Same value")
} else {
    print("Not the same")
}

Answer 9

You could also make all the letters uppercase (or lowercase) and see if they are the same.

var a = “Cash”
var b = “CASh”

if a.uppercaseString == b.uppercaseString{
  //DO SOMETHING
}

This will make both variables as ”CASH” and thus they are equal.

You could also make a String extension

extension String{
  func equalsIgnoreCase(string:String) -> Bool{
    return self.uppercaseString == string.uppercaseString
  }
}

if "Something ELSE".equalsIgnoreCase("something Else"){
  print("TRUE")
}

Answer 10

Swift 4, I went the String extension route using caseInsensitiveCompare() as a template (but allowing the operand to be an optional). Here's the playground I used to put it together (new to Swift so feedback more than welcome).

import UIKit

extension String {
    func caseInsensitiveEquals<T>(_ otherString: T?) -> Bool where T : StringProtocol {
        guard let otherString = otherString else {
            return false
        }
        return self.caseInsensitiveCompare(otherString) == ComparisonResult.orderedSame
    }
}

"string 1".caseInsensitiveEquals("string 2") // false

"thingy".caseInsensitiveEquals("thingy") // true

let nilString1: String? = nil
"woohoo".caseInsensitiveEquals(nilString1) // false

Answer 11

You can just write your String Extension for comparison in just a few line of code

extension String {

    func compare(_ with : String)->Bool{
        return self.caseInsensitiveCompare(with) == .orderedSame
    } 
}

Answer 12

For Swift 5 Ignoring the case and compare two string

var a = "cash"
var b = "Cash"
if(a.caseInsensitiveCompare(b) == .orderedSame){
     print("Ok")
}

Answer 13

Swift 3 : You can define your own operator, eg ~= .

infix operator ~=

func ~=(lhs: String, rhs: String) -> Bool {
   return lhs.caseInsensitiveCompare(rhs) == .orderedSame
}

Which you then can try in a playground

let low = "hej"
let up = "Hej"

func test() {
    if low ~= up {
        print("same")
    } else {
        print("not same")
    }
}

test() // prints 'same'

Answer 14

Swift 3

if a.lowercased() == b.lowercased() {

}

Answer 15

extension String
{
    func equalIgnoreCase(_ compare:String) -> Bool
    {
        return self.uppercased() == compare.uppercased()
    }
}

sample of use

print("lala".equalIgnoreCase("LALA"))
print("l4la".equalIgnoreCase("LALA"))
print("laLa".equalIgnoreCase("LALA"))
print("LALa".equalIgnoreCase("LALA"))

Answer 16

Swift 3:

You can also use the localized case insensitive comparison between two strings function and it returns Bool

var a = "cash"
var b = "Cash"

if a.localizedCaseInsensitiveContains(b) {
    print("Identical")           
} else {
    print("Non Identical")
}