add 'removeTransactionsForProductIdentifier' to RMStoreUserDefaultsPersistence robotmedia#175

Author: everappz

RMStore/Optional/RMStoreUserDefaultsPersistence.h

@@ -34,6 +34,10 @@
  */
 - (void)removeTransactions;
 
+/** Remove transactions from user defaults via specific ProductIdentifier.
+ */
+- (void)removeTransactionsForProductIdentifier:(NSString *)productIdentifier;
+
 /** Consume the given product if available. Intended for consumable products.
  @param productIdentifier Identifier of the product to be consumed.
  @return YES if the product was consumed, NO otherwise.

RMStore/Optional/RMStoreUserDefaultsPersistence.m

@@ -53,6 +53,15 @@ - (void)removeTransactions
     [defaults synchronize];
 }
 
+- (void)removeTransactionsForProductIdentifier:(NSString *)productIdentifier{
+    NSUserDefaults *defaults = [self userDefaults];
+    NSDictionary *purchases = [defaults objectForKey:RMStoreTransactionsUserDefaultsKey] ? : @{};
+    NSMutableDictionary *updatedPurchases = [NSMutableDictionary dictionaryWithDictionary:purchases];
+    [updatedPurchases removeObjectForKey:productIdentifier];
+    [defaults setObject:updatedPurchases forKey:RMStoreTransactionsUserDefaultsKey];
+    [defaults synchronize];
+}
+
 - (BOOL)consumeProductOfIdentifier:(NSString*)productIdentifier
 {
     NSUserDefaults *defaults = [self userDefaults];