DataCenter FAQs

Common troubleshooting questions for iOS developers using the DataCenter component in mPaaS.

How do I use a DataCenter API to set the storage directory?

DataCenter organizes stored data by user ID. Call setCurrentUserId: to point DataCenter to the correct database whenever the active user switches. Call this before any business layer reads or writes data.

[[APDataCenter defaultDataCenter] setCurrentUserId:userId];

On sign out, you do not need to clear the user ID. DataCenter continues using the database of the last active user.

How do I set the default encryption key?

DataCenter encrypts data by default. If you do not provide a key, DataCenter derives one from appKey (passed to mPaasInit), which is secure. For stronger control, supply your own 32-byte key.

Enabling

Implement appDataCenterDefaultCryptKey in the mPaasAppInterface API to return the key as NSData:

#pragma mark DataCenter

/**
 * If you implement this method, return the default encryption key (32 bytes) used by DataCenter.
 * You can manage this key with Security Guard, or encrypt and obfuscate it before writing it to the client.
 * If you do not implement this method, DataCenter uses a key derived from mPaaS and appKey, which is also secure.
 *
 * @return The 32-byte key stored in NSData.
 */
- (NSData*)appDataCenterDefaultCryptKey;

Persisting

Generate a 32-byte key, encode it as a Base64 string, and store it in Security Guard. At runtime, retrieve and parse it into NSData using a Security Guard static API.

Is DataCenter thread-safe?

Yes. All public DataCenter storage APIs are thread-safe and can be called from any thread without additional synchronization.

How do I resolve the conflict with the Baidu Maps SDK?

Integrating certain versions of the Baidu Maps SDK causes a crash at app startup.

Add the following code during app initialization. Requires mPaaS 10.1.32 or later.

#import <MPDataCenter/APDataCenter.h>
// Add the following code to the app initialization method.
APDataCenter.compatibility = YES;

How does archiveObject store and read variables?

Use APUserPreferences to persist and retrieve objects with archiveObject.

• Store the object:

  MPCodingData *obj = [MPCodingData new];
  obj.name = @"Amelia";
  obj.age = 1;
  [APUserPreferences archiveObject:obj forKey:@"archObjKey" business:dataBusiness];

Read it back from DataCenter:

MPCodingData *encodeObj = [APUserPreferences objectForKey:@"archObjKey" business:dataBusiness];