Add collation operator

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Author: stephencelis

SQLite Common Tests/ExpressionTests.swift

@@ -243,6 +243,13 @@ class ExpressionTests: XCTestCase {
         ExpectExecutionMatches(db, "('Hello' MATCH 'ello')", query)
     }
 
+    func test_collateOperator_withStringExpression_buildsCollationExpression() {
+        let string = Expression<String>(value: "Hello ")
+        ExpectExecutionMatches(db, "('Hello ' COLLATE BINARY)", users.select(collate(.Binary, string)))
+        ExpectExecutionMatches(db, "('Hello ' COLLATE NOCASE)", users.select(collate(.NoCase, string)))
+        ExpectExecutionMatches(db, "('Hello ' COLLATE RTRIM)", users.select(collate(.RTrim, string)))
+    }
+
     func test_doubleAndOperator_withBooleanExpressions_buildsCompoundExpression() {
         let bool = Expression<Bool>(value: true)
         let query = users.select(bool && bool)

SQLite Common/Expression.swift

@@ -174,6 +174,20 @@ public prefix func ~(rhs: Expression<Int>) -> Expression<Int> {
     return wrap(__FUNCTION__, rhs)
 }
 
+public enum Collation: String {
+
+    case Binary = "BINARY"
+
+    case NoCase = "NOCASE"
+
+    case RTrim = "RTRIM"
+
+}
+
+public func collate(collation: Collation, expression: Expression<String>) -> Expression<String> {
+    return infix("COLLATE", expression, Expression(collation.rawValue))
+}
+
 // MARK: - Predicates
 
 public func ==<T: protocol<Value, Equatable>>(lhs: Expression<T>, rhs: Expression<T>) -> Expression<Bool> {