Prevent update block called on first time app installed.

MTMigration/MTMigration.h

@@ -44,6 +44,16 @@ typedef void (^MTExecutionBlock)(void);
 
 + (void) applicationUpdateBlock:(MTExecutionBlock)updateBlock;
 
+/**
+
+ Executes a block of code for every time the application version changes.
+
+ @param updateBlock A block object to be executed when the application version changes. This parameter can't be nil.
+ @param ignoreFirstInstall Set to YES to not run the updateBlock when no app version is found. This is useful to avoid calling the updateBlock on first time install. Calling with NO, will have same effect as calling applicationUpdateBlock:(MTExecutionBlock)updateBlock;
+ */
+
++ (void) applicationUpdateBlock:(MTExecutionBlock)updateBlock ignoreFirstInstall:(BOOL)ignoreFirstInstall;
+
 /**
 
  Executes a block of code for every time the application build number changes.

MTMigration/MTMigration.m

@@ -51,13 +51,29 @@ + (void) migrateToBuild:(NSString *)build block:(MTExecutionBlock)migrationBlock
 
 
 + (void) applicationUpdateBlock:(MTExecutionBlock)updateBlock {
-    if (![[self lastAppVersion] isEqualToString:[self appVersion]]) {
-        updateBlock();
+
+    [self applicationUpdateBlock:updateBlock ignoreFirstInstall:NO];
+}
 
-        #if DEBUG
++ (void) applicationUpdateBlock:(MTExecutionBlock)updateBlock ignoreFirstInstall:(BOOL)ignoreFirstInstall {
+
+    BOOL lastAppVersionExists = ![[self lastAppVersion] isEqualToString:@""];
+    BOOL performCheck = lastAppVersionExists || !ignoreFirstInstall;
+
+    if(performCheck) {
+
+        BOOL appVersionDifferent = ![[self lastAppVersion] isEqualToString:[self appVersion]];
+        if (appVersionDifferent) {
+            updateBlock();
+
+#if DEBUG
             NSLog(@"MTMigration: Running update Block for version %@", [self appVersion]);
-        #endif
-
+#endif
+
+            [self setLastAppVersion:[self appVersion]];
+        }
+    } else {
+
         [self setLastAppVersion:[self appVersion]];
     }
 }

MTMigrationTests/MTMigrationTests.m

@@ -8,19 +8,46 @@
 
 #import "MTMigrationTests.h"
 #import "MTMigration.h"
+#import <objc/runtime.h>
 
-#define kDefaultWaitForExpectionsTimeout 2.0
+#define kDefaultWaitForExpectionsTimeout    2.0
+#define kBundleShortVersionStringKey        @"CFBundleShortVersionString"
+#define kBundleVersionKey                   @"CFBundleVersion"
 
 @implementation MTMigrationTests
 
+#define makr - Setup/TearDown
+
 - (void)setUp {
 
     [super setUp];
+    [self setUpMockBundle];
     [MTMigration reset];
 }
 
-- (void)testMigrationReset
-{
+- (void)setUpMockBundle {
+
+    [self swapOutBundleMethods];
+}
+
+- (void)tearDown {
+
+    [self tearDownMockBundle];
+    [super tearDown];
+}
+
+- (void)tearDownMockBundle {
+
+    [self swapInBundleMethods];
+    [self setMainBundleAppBuild:nil];
+    [self setMainBundleAppVersion:nil];
+}
+
+#pragma mark - Test migrateToVersion
+
+- (void)testMigrationReset {
+
+    [self setMainBundleAppVersion:@"1.0"];
 
     XCTestExpectation *expectingBlock1Run = [self expectationWithDescription:@"Expecting block to be run for version 0.9"];
 	[MTMigration migrateToVersion:@"0.9" block:^{
@@ -47,8 +74,9 @@ - (void)testMigrationReset
     [self waitForAllExpectations];
 }
 
-- (void)testMigratesOnFirstRun
-{
+- (void)testMigratesOnFirstRun {
+
+    [self setMainBundleAppVersion:@"1.0"];
 
     XCTestExpectation *expectationBlockRun = [self expectationWithDescription:@"Should execute migration after reset"];
 	[MTMigration migrateToVersion:@"1.0" block:^{
@@ -58,8 +86,9 @@ - (void)testMigratesOnFirstRun
     [self waitForAllExpectations];
 }
 
-- (void)testMigratesOnce
-{
+- (void)testMigratesOnce {
+
+    [self setMainBundleAppVersion:@"1.0"];
 
     XCTestExpectation *expectationBlockRun = [self expectationWithDescription:@"Expecting block to be run"];
 	[MTMigration migrateToVersion:@"1.0" block:^{
@@ -73,8 +102,17 @@ - (void)testMigratesOnce
     [self waitForAllExpectations];
 }
 
-- (void)testMigratesPreviousBlocks
-{
+- (void)testMigrateToVersionWontRunForLowerAppVersions {
+
+    [self setMainBundleAppVersion:@"0.1"];
+    [MTMigration migrateToVersion:@"1.0" block:^{
+        XCTFail(@"Should not execute a block for the same version twice.");
+    }];
+}
+
+- (void)testMigratesPreviousBlocks {
+
+    [self setMainBundleAppVersion:@"1.0"];
 
     XCTestExpectation *expectingBlock1Run = [self expectationWithDescription:@"Expecting block to be run for version 0.9"];
 	[MTMigration migrateToVersion:@"0.9" block:^{
@@ -92,6 +130,8 @@ - (void)testMigratesPreviousBlocks
 - (void)testMigratesInNaturalSortOrder
 {
 
+    [self setMainBundleAppVersion:@"1.0"];
+
     XCTestExpectation *expectingBlock1Run = [self expectationWithDescription:@"Expecting block to be run for version 0.9"];
 	[MTMigration migrateToVersion:@"0.9" block:^{
         [expectingBlock1Run fulfill];
@@ -109,9 +149,12 @@ - (void)testMigratesInNaturalSortOrder
     [self waitForAllExpectations];
 }
 
-- (void)testRunsApplicationUpdateBlockOnce
-{
+#pragma mark - Test applicationUpdateBlock
 
+- (void)testRunsApplicationUpdateBlockOnce {
+
+    [self setMainBundleAppVersion:@"1.0"];
+
     XCTestExpectation *expectationBlockRun = [self expectationWithDescription:@"Should only call block once"];
     [MTMigration applicationUpdateBlock:^{
         [expectationBlockRun fulfill];
@@ -124,9 +167,10 @@ - (void)testRunsApplicationUpdateBlockOnce
     [self waitForAllExpectations];
 }
 
-- (void)testRunsApplicationUpdateBlockeOnlyOnceWithMultipleMigrations
-{
+- (void)testRunsApplicationUpdateBlockeOnlyOnceWithMultipleMigrations {
 
+    [self setMainBundleAppVersion:@"1.0"];
+
     [MTMigration migrateToVersion:@"0.8" block:^{
 		// Do something
 	}];
@@ -147,11 +191,77 @@ - (void)testRunsApplicationUpdateBlockeOnlyOnceWithMultipleMigrations
     [self waitForAllExpectations];
 }
 
+- (void)testRunsApplicationBlockButIgnoresFirstTimeInstall {
+
+    [self setMainBundleAppVersion:@"1.0"];
+
+    [MTMigration applicationUpdateBlock:^{
+        XCTFail(@"Expected on first install, this block will never run.");
+    } ignoreFirstInstall:YES];
+
+    [self setMainBundleAppVersion:@"1.1"];
+
+    XCTestExpectation *expectation = [self expectationWithDescription:@"Expect block to be run"];
+    [MTMigration applicationUpdateBlock:^{
+        [expectation fulfill];
+    } ignoreFirstInstall:YES];
+
+    [self waitForAllExpectations];
+}
+
 - (void)waitForAllExpectations {
 
     [self waitForExpectationsWithTimeout:kDefaultWaitForExpectionsTimeout handler:^(NSError *error) {
         //do nothing
     }];
 }
 
+#pragma mark - Methods used to mock [NSBundle mainBundle] values
+static NSString *mockAppVersion;
+static NSString *mockAppBuild;
+
+- (void)setMainBundleAppVersion:(NSString *)appVersion {
+    mockAppVersion = appVersion;
+}
+
+- (void)setMainBundleAppBuild:(NSString *)appBuild {
+    mockAppBuild = appBuild;
+}
+
+// The following methods use a technique called method swizzling (http://nshipster.com/method-swizzling/) and
+// provide the only way in which the tests can manipulate the application version and build number in our static class
+//
+// In summary, the method `objectForInfoDictionaryKey` is swapped with this class's method `swizzled_objectForInfoDictionaryKey`
+// allowing the test method to intercept this method call and provide appropriate mock responses.
+
+- (void)swapOutBundleMethods {
+
+    method_exchangeImplementations(class_getInstanceMethod([NSBundle class], @selector(objectForInfoDictionaryKey:)),
+                                   class_getInstanceMethod([MTMigrationTests class], @selector(swizzled_objectForInfoDictionaryKey:)));
+}
+
+- (void)swapInBundleMethods {
+
+    method_exchangeImplementations(class_getInstanceMethod([MTMigrationTests class], @selector(swizzled_objectForInfoDictionaryKey:)),
+                                   class_getInstanceMethod([NSBundle class], @selector(objectForInfoDictionaryKey:)));
+}
+
+- (id)swizzled_objectForInfoDictionaryKey:(NSString *)key {
+
+    if ([key isEqualToString:kBundleVersionKey] && mockAppBuild) {
+
+        return mockAppBuild;
+
+    } else if ([key isEqualToString:kBundleShortVersionStringKey] && mockAppVersion) {
+
+        return mockAppVersion;
+
+    } else {
+
+        XCTFail(@"Mock bundle is missing a mock key/value pair");
+    }
+
+    return nil;
+}
+
 @end