Data commit

Task/Substring/Swift/substring.swift

@@ -0,0 +1,57 @@
+let string = "Hello, Swift language"
+let (n, m) = (5, 4)
+
+// Starting from `n` characters in and of `m` length.
+do {
+  let start = string.startIndex.advancedBy(n)
+  let end = start.advancedBy(m)
+  // Pure-Swift (standard library only):
+  _ = string[start..<end]
+  // With Apple's Foundation framework extensions:
+  string.substringWithRange(start..<end)
+}
+
+// Starting from `n` characters in, up to the end of the string.
+do {
+  // Pure-Swift (standard library only):
+  _ = String(
+    string.characters.suffix(string.characters.count - n)
+  )
+  // With Apple's Foundation framework extensions:
+  _ = string.substringFromIndex(string.startIndex.advancedBy(n))
+}
+
+// Whole string minus last character.
+do {
+  // Pure-Swift (standard library only):
+  _ = String(
+    string.characters.prefix(
+      string.characters.count.predecessor()
+    )
+  )
+  // With Apple's Foundation framework extensions:
+  _ = string.substringToIndex(string.endIndex.predecessor())
+}
+
+// Starting from a known character within the string and of `m` length.
+do {
+  // Pure-Swift (standard library only):
+  let character = Character("l")
+  guard let characterIndex = string.characters.indexOf(character) else {
+    fatalError("Index of '\(character)' character not found.")
+  }
+  let endIndex = characterIndex.advancedBy(m)
+  _ = string[characterIndex..<endIndex]
+}
+
+// Starting from a known substring within the string and of `m` length.
+do {
+  // With Apple's Foundation framework extensions:
+  let substring = "Swift"
+  guard let range = string.rangeOfString(substring) else {
+    fatalError("Range of substring \(substring) not found")
+  }
+  let start = range.startIndex
+  let end = start.advancedBy(m)
+  string[start..<end]
+}