Question

How to check if a word is all uppercase or lowercase or capitalized in Swift

Answer 1

import Foundation

func verifyCasing(_ word: String) -> Bool {
    let upper = word.filter { $0.isUppercase }.count
    let lower = word.filter { $0.isLowercase }.count

    // Case 1: all lowercase
    if upper == 0 { return true }

    // Case 2: all uppercase
    if lower == 0 { return true }

    // Case 3: capitalized (only first letter uppercase)
    if upper == 1, let first = word.first, first.isUppercase {
        return true
    }

    // Otherwise, mixed casing
    return false
}

func runTest(_ word: String) {
    print("Testing word: \"\(word)\"")
    if verifyCasing(word) {
        print("OK\n")
    } else {
        print("Error\n")
    }
}

runTest("PROGRAMMING")  
runTest("programming")   
runTest("Programming")   
runTest("ProGramMing")   



/*
run:
 
Testing word: "PROGRAMMING"
OK

Testing word: "programming"
OK

Testing word: "Programming"
OK

Testing word: "ProGramMing"
Error

 
*/

 

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