Merge pull request kodecocodes#187 from mrkbxt/master

migrate palindromes to Swift 3 string. Thanks @mrkbxt!

Author: kelvinlauKL

Palindromes/Palindromes.playground/Contents.swift

@@ -2,7 +2,7 @@ import Cocoa
 
 public func palindromeCheck (text: String?) -> Bool {
   if let text = text {
-    let mutableText = text.stringByTrimmingCharactersInSet(.whitespaceCharacterSet()).lowercaseString
+    let mutableText = text.trimmingCharacters(in: NSCharacterSet.whitespaces()).lowercased()
     let length: Int = mutableText.characters.count
 
     guard length >= 1 else {
@@ -11,26 +11,26 @@ public func palindromeCheck (text: String?) -> Bool {
 
     if length == 1 {
       return true
-    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.endIndex.predecessor()] {
-      let range = Range<String.Index>(mutableText.startIndex.successor()..<mutableText.endIndex.predecessor())
-      return palindromeCheck(mutableText.substringWithRange(range))
+    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.index(mutableText.endIndex, offsetBy: -1)] {
+      let range = Range<String.Index>(mutableText.index(mutableText.startIndex, offsetBy: 1)..<mutableText.index(mutableText.endIndex, offsetBy: -1))
+      return palindromeCheck(text: mutableText.substring(with: range))
     }
   }
 
   return false
 }
 
 // Test to check that non-palindromes are handled correctly:
-palindromeCheck("owls")
+palindromeCheck(text: "owls")
 
 // Test to check that palindromes are accurately found (regardless of case and whitespace:
-palindromeCheck("lol")
-palindromeCheck("race car")
-palindromeCheck("Race fast Safe car")
+palindromeCheck(text: "lol")
+palindromeCheck(text: "race car")
+palindromeCheck(text: "Race fast Safe car")
 
 // Test to check that palindromes are found regardless of case:
-palindromeCheck("HelloLLEH")
+palindromeCheck(text: "HelloLLEH")
 
 // Test that nil and empty Strings return false:
-palindromeCheck("")
-palindromeCheck(nil)
+palindromeCheck(text: "")
+palindromeCheck(text: nil)

Palindromes/Palindromes.swift

@@ -2,7 +2,7 @@ import Cocoa
 
 public func palindromeCheck (text: String?) -> Bool {
   if let text = text {
-    let mutableText = text.stringByTrimmingCharactersInSet(.whitespaceCharacterSet()).lowercaseString
+    let mutableText = text.trimmingCharacters(in: NSCharacterSet.whitespaces()).lowercased()
     let length: Int = mutableText.characters.count
 
     guard length >= 1 else {
@@ -11,9 +11,9 @@ public func palindromeCheck (text: String?) -> Bool {
 
     if length == 1 {
       return true
-    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.endIndex.predecessor()] {
-      let range = Range<String.Index>(mutableText.startIndex.successor()..<mutableText.endIndex.predecessor())
-      return palindromeCheck(mutableText.substringWithRange(range))
+    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.index(mutableText.endIndex, offsetBy: -1)] {
+      let range = Range<String.Index>(mutableText.index(mutableText.startIndex, offsetBy: 1)..<mutableText.index(mutableText.endIndex, offsetBy: -1))
+      return palindromeCheck(text: mutableText.substring(with: range))
     }
   }
 

Palindromes/README.markdown

@@ -28,18 +28,18 @@ Here is a recursive implementation of this in Swift:
 ```swift
 func palindromeCheck (text: String?) -> Bool {
   if let text = text {
-    let mutableText = text.stringByTrimmingCharactersInSet(.whitespaceCharacterSet()).lowercaseString
+    let mutableText = text.trimmingCharacters(in: NSCharacterSet.whitespaces()).lowercased()
     let length: Int = mutableText.characters.count
 
-    guard length >= 1 {
+    guard length >= 1 else {
       return false
     }
 
     if length == 1 {
       return true
-    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.endIndex.predecessor()] {
-      let range = Range<String.Index>(mutableText.startIndex.successor()..<mutableText.endIndex.predecessor())
-      return palindromeCheck(mutableText.substringWithRange(range))
+    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.index(mutableText.endIndex, offsetBy: -1)] {
+      let range = Range<String.Index>(mutableText.index(mutableText.startIndex, offsetBy: 1)..<mutableText.index(mutableText.endIndex, offsetBy: -1))
+      return palindromeCheck(text: mutableText.substring(with: range))
     }
   }
 
@@ -51,7 +51,7 @@ func palindromeCheck (text: String?) -> Bool {
 This code can be tested in a playground using the following: 
 
 ```swift
-palindromeCheck("Race car")
+palindromeCheck(text: "Race car")
 ```
 
 Since the phrase "Race car" is a palindrome, this will return true.