How to check the string doesn’t contain any letters in swift?

i have trouble during making the letter checker, my code is like this: if !containLetters(“1234h”){print(“pass”)}

my function is

    func containsOnlyNum(input: String) -> Bool {
         var ok = false
         for chr in input {
             for check in "1234567890.-"{
                if chr == check{
                    ok = true
                }
             }
             if ok != true{
                 return false
             }
         }
         return true
    }

If I check for “h” then didn’t pass, but if i check for ”1h” then it still pass! Please help me to fix this problem. I will give a big thank for anyone who helped me

>Solution :

The simplest way to fix the algorithm is this way:

func containsOnlyNum(input: String) -> Bool {
     // check every character
     for chr in input {
         var isNum = false
         
         for check in "1234567890.-"{
            if chr == check {
                isNum = true
                // if we have found a valid one, we can break the iteration
                break
            }
         }
         
         if !isNum {
             return false
         }
     }
    
     return true
}


print(containsOnlyNum(input: "1234")) // true
print(containsOnlyNum(input: "1234h")) // false

However, then you can directly simplify it to:

func containsOnlyNum(input: String) -> Bool {
    return input.allSatisfy { chr in
        "1234567890.-".contains(chr)
    }
}

which does exatly the same but uses allSatisfy and contains functions, which represent the logical operators ALL and EXISTS.

However, programmers normally use regular expressions for similar tasks:

func containsOnlyNum(input: String) -> Bool {
    return input.range(of: "^[0-9.\\-]+$", options: .regularExpression) != nil
}