String comparison in Swift and Objective-C

gistfile1.swift

// Lets start by comparing the same string in Swift.
// Unicode defines U+00E9, Latin small letter e with acute, as a single value. 
// But you can also write it as the plain letter e, followed by U+0301, combining acute accent.
// In both cases, what’s displayed is é, and a user probably has a reasonable expectation 
// that two strings displayed as “résumé” would not only be equal to each other but also 
// have a “length” of six characters, no matter which technique was used to produce the é in either one.
// They would be what the Unicode specification describes as canonically equivalent.

    let single = "Pok\u{00E9}mon"
    let double = "Poke\u{0301}mon"
    if(single == double)
    {
        print("They are equal")
    }
// Lets try the same thing in Objective-C    
    let nssingle = single as NSString
    nssingle.length // → 7
    let nsdouble = double as NSString
    nsdouble.length // → 8
    if(nssingle == nsdouble)
    {
        print("They are equal NS")
    }
    else
    {
        print("they are not equal NS") // This will be printed.
// The strings will not be printed, because of the == operator implementation in objective-c
// Both the strings will be compared literally. So they will fail to match.        
    }

// This is how we fix it. Use compares to check the values of the strings.
    if(nssingle.compare(String(nsdouble)) == ComparisonResult.orderedSame)
    {
        print("They are equal")
    }