add method for cleaning Leanplum_Resources cache folder on every new … (#353)

* add method for cleaning Leanplum_Resources cache folder on every new version of the sdk

* changing the place where clearCacheIfNeeded method is called.
Instead of calling it in start method now it is called in startWith.... method because this method is doing all the work for starting the sdk

* changing the name of the method to be more understandable

Author: dejan2k

Leanplum-SDK/Classes/Internal/Leanplum.m

@@ -742,6 +742,8 @@ + (void)startWithUserId:(NSString *)userId
         return;
     }
 
+    [LPFileManager clearCacheIfSDKUpdated];
+    
     [[LPCountAggregator sharedAggregator] incrementCount:@"start_with_user_id"];
 
     LP_TRY

Leanplum-SDK/Classes/Managers/LPFileManager.h

@@ -81,5 +81,5 @@
  * Adds an attribute to a file at filepath to exclude it from iCloud and iTunes backup.
  */
 + (BOOL)addSkipBackupAttributeToItemAtPath:(NSString *__nonnull) filePathString;
-
++ (void)clearCacheIfSDKUpdated;
 @end

Leanplum-SDK/Classes/Managers/LPFileManager.m

@@ -856,4 +856,27 @@ + (BOOL)addSkipBackupAttributeToItemAtPath:(NSString *) filePathString
     LP_END_TRY
 }
 
++ (void)clearCacheIfSDKUpdated {
+    NSString *savedSdkVersionKey = @"savedSdkVersion";
+    NSString *savedSdkVersion = [[NSUserDefaults standardUserDefaults] valueForKey:savedSdkVersionKey];
+    if(![[LPConstantsState sharedState].sdkVersion isEqualToString:savedSdkVersion]) {
+        [[NSUserDefaults standardUserDefaults] setValue:[LPConstantsState sharedState].sdkVersion forKey:savedSdkVersionKey];
+        [[NSUserDefaults standardUserDefaults] synchronize];
+        NSString *cachesDir = [[self cachesDirectory] stringByAppendingPathComponent:@"Leanplum_Resources"];
+        
+        NSFileManager *fileManager = [[NSFileManager alloc] init];
+        NSDirectoryEnumerator *enumerator = [fileManager enumeratorAtPath:cachesDir];
+        NSString *file;
+
+        while (file = [enumerator nextObject]) {
+            NSError *error = nil;
+            BOOL result = [fileManager removeItemAtPath:[cachesDir stringByAppendingPathComponent:file] error:&error];
+
+            if (!result && error) {
+                NSLog(@"Cleaning cache error: %@, for file %@", error, file);
+            }
+        }
+    }
+}
+
 @end