added telephone number formatter

Signed-off-by: Matt Bruce <mbrucedogs@gmail.com>

EmployeeDirectory/Extensions/String.swift

@@ -0,0 +1,40 @@
+//
+//  String.swift
+//  EmployeeDirectory
+//
+//  Created by Matt Bruce on 1/20/25.
+//
+
+import Foundation
+
+extension String {
+    /// Formats a string into a US phone number format (XXX-XXX-XXXX).
+    /// Non-numeric characters are removed, and formatting is applied based on the length of the string.
+    /// - Returns: A formatted phone number as a string.
+    internal func formatUSNumber() -> String {
+        // format the number
+        return format(with: "XXX-XXX-XXXX", phone: self)
+    }
+    
+    internal func format(with mask: String, phone: String) -> String {
+        let numbers = filter { $0.isNumber }
+        var result = ""
+        var index = numbers.startIndex // numbers iterator
+
+        // iterate over the mask characters until the iterator of numbers ends
+        for ch in mask where index < numbers.endIndex {
+            if ch == "X" {
+                // mask requires a number in this place, so take the next one
+                result.append(numbers[index])
+
+                // move numbers iterator to the next index
+                index = numbers.index(after: index)
+
+            } else {
+                result.append(ch) // just append a mask character
+            }
+        }
+        return result
+    }
+}
+

EmployeeDirectory/ViewModels/EmployeeCellViewModel.swift

@@ -27,7 +27,7 @@ public class EmployeeCellViewModel: ObservableObject {
         // Initialize properties
         self.uuid = employee.uuid.uuidString
         self.fullName = employee.fullName
-        self.phoneNumber = employee.phoneNumber
+        self.phoneNumber = employee.phoneNumber?.formatUSNumber()
         self.emailAddress = employee.emailAddress
         self.biography = employee.biography
         self.team = employee.team