(DOCSP-15555): Add "thaw" to frozen object documentation (#1008)

Author: dacharyc

examples/ios/Examples/Threading.swift

@@ -91,6 +91,47 @@ class Threading: XCTestCase {
         // :code-block-end:
     }
 
+    func testThaw() {
+        let realm = try! Realm()
+
+        try! realm.write {
+            realm.add(Task())
+        }
+
+        let frozenRealm = realm.freeze()
+
+        // :code-block-start: thaw
+        // Read from a frozen realm
+        let frozenTasks = frozenRealm.objects(Task.self)
+
+        // The collection that we pull from the frozen realm is also frozen
+        assert(frozenTasks.isFrozen)
+
+        // Get an individual task from the collection
+        let frozenTask = frozenTasks.first!
+
+        // To modify the task, you must first thaw it
+        // You can also thaw collections and realms
+        let thawedTask = frozenTask.thaw()
+
+        // Check to make sure this task is valid. An object is
+        // invalidated when it is deleted from its managing realm,
+        // or when its managing realm has invalidate() called on it.
+        assert(thawedTask?.isInvalidated == false)
+
+        // Thawing the task also thaws the frozen realm it references
+        assert(thawedTask!.realm!.isFrozen == false)
+
+        // Let's make the code easier to follow by naming the thawed realm
+        let thawedRealm = thawedTask!.realm!
+
+        // Now, you can modify the task
+        try! thawedRealm.write {
+           thawedTask!.status = "Done"
+        }
+        // :code-block-end:
+    }
+
     func testPassAcrossThreads() {
         let expectation = XCTestExpectation(description: "it completes")
         // :code-block-start: pass-across-threads