Merge pull request #6 from daehn/feature/return-if-count-changed

Return whether or not the count changed
daehn · Sep 15, 2017 · 04a2b7c · 04a2b7c
2 parents 397aa51 + ad89c71
commit 04a2b7c
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Showing 2 changed files with 20 additions and 3 deletions.
diff --git a/CountedSet/CountedSet.swift b/CountedSet/CountedSet.swift
@@ -55,15 +55,18 @@ public struct CountedSet<Element : Hashable> : ExpressibleByArrayLiteral {
         return count(for: member)
     }
 
-    public mutating func setCount(_ count: Int, for element: Element) {
+    @discardableResult public mutating func setCount(_ count: Int, for element: Element) -> Bool {
         precondition(count >= 0, "Count has to be positive")
+        guard count != countByElement[element] else { return false }
+
         if count > 0 && !contains(element) {
             backing.insert(element)
         }
         countByElement[element] = count
         if count <= 0 {
             backing.remove(element)
         }
+        return true
     }
 
     public func mostFrequent() -> ElementWithCount? {

diff --git a/CountedSetTests/CountedSetTests.swift b/CountedSetTests/CountedSetTests.swift
@@ -261,16 +261,30 @@ class CountedSetTests: XCTestCase {
         // given
         sut = CountedSet(arrayLiteral: "Foo", "Bar")
         // when
-        sut.setCount(3, for: "Foo")
+        XCTAssert(sut.setCount(3, for: "Foo"))
         // then
         XCTAssertEqual(sut.count(for: "Foo"), 3)
     }
+
+    func testThatItReturnsFalseWhenSettingExistingCount() {
+        // given
+        sut = CountedSet(arrayLiteral: "Foo", "Bar", "Foo")
+        // then
+        XCTAssertFalse(sut.setCount(2, for: "Foo"))
+    }
+
+    func testThatItReturnsTrueWhenSettingCountForElementWithDifferentExistingCount() {
+        // given
+        sut = CountedSet(arrayLiteral: "Foo", "Bar")
+        // then
+        XCTAssert(sut.setCount(2, for: "Foo"))
+    }
 
     func testThatItRemovesElementFrombackingStoreWhenSettingCountForContainedElementToZero() {
         // given
         sut = CountedSet(arrayLiteral: "Foo", "Bar")
         // when
-        sut.setCount(0, for: "Foo")
+        XCTAssert(sut.setCount(0, for: "Foo"))
         // then
         XCTAssertFalse(sut.contains("Foo"))
         XCTAssertEqual(sut.count(for: "Foo"), 0)