iOS_tutorial

MMKV for iOS/macOS

MMKV is an efficient, small, easy-to-use mobile key-value storage framework used in the WeChat application. It's currently available on both Android, iOS/macOS, Win32 and POSIX.

Turtorial

You can use MMKV as you go. All changes are saved immediately, no synchronize calls needed.

Configuration

• Setup MMKV on App startup, in your -[MyApp application: didFinishLaunchingWithOptions:], add these lines:

  - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
      // init MMKV in the main thread
      [MMKV initializeMMKV:nil];
  
      //...
      return YES;
  }

• If multi-process accessing is needed(between the App and extensions)，you need to set the group directory on MMKV initialization:

  NSString *myGroupID = @"group.company.mmkv";
  // the group dir that can be accessed by App & extensions
  NSString *groupDir = [[NSFileManager defaultManager] containerURLForSecurityApplicationGroupIdentifier:myGroupID].path;
  [MMKV initializeMMKV:nil groupDir:groupDir logLevel:MMKVLogInfo];

  Notice: When using MMKV in App Extensions, you should link MMKV to your target by static linking(aka libMMKV Static.a). If you prefer dynamic frameworks, you should add the MMKVAppExtensions framework to your target instead(either by source or by Carthage).

CRUD Operations

• MMKV has a default instance, which could be used directly:

  MMKV *mmkv = [MMKV defaultMMKV];
  
  [mmkv setBool:YES forKey:@"bool"];
  NSLog(@"bool:%d", [mmkv getBoolForKey:@"bool"]);
  
  [mmkv setInt32:-1024 forKey:@"int32"];
  NSLog(@"int32:%d", [mmkv getInt32ForKey:@"int32"]);
  
  [mmkv setInt64:std::numeric_limits<int64_t>::min() forKey:@"int64"];
  NSLog(@"int64:%lld", [mmkv getInt64ForKey:@"int64"]);
  
  [mmkv setFloat:-3.1415926 forKey:@"float"];
  NSLog(@"float:%f", [mmkv getFloatForKey:@"float"]);
  
  [mmkv setString:@"hello, mmkv" forKey:@"string"];
  NSLog(@"string:%@", [mmkv getStringForKey:@"string"]);
  
  [mmkv setDateorKey:@"date"];
  NSLog(@"date:%@", [mmkv getDateForKey:@"date"]);
  
  NSData *data = [@"hello, mmkv again and again" dataUsingEncoding:NSUTF8StringEncoding];
  [mmkv setDataForKey:@"data"];
  data = [mmkv getDataForKey:@"data"];

NSLog(@"data:%@", [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);

NSDictionary *dic = @{@"key1" : @"value1",
                      @"key2" : @(2)};
[mmkv setObject:dic forKey:@"dictionary"];
dic = [mmkv getObjectOfClass:[NSDictionary class] forKey:@"dictionary"];
NSLog(@"dictionary:%@", dic);

```

As you can see，MMKV is quite simple to use.

• Deleting, Querying & Enumerating:

  MMKV *mmkv = [MMKV defaultMMKV];
  
  [mmkv removeValueForKey:@"bool"];
  [mmkv removeValuesForKeys:@[@"int32", @"int64"]];
  
  BOOL hasBool = [mmkv containsKey:@"bool"];
      
  [mmkv enumerateKeys:^(NSString *key, BOOL *stop) {
      if ([key isEqualToString:@"string"]) {
          NSString *value = [mmkv getStringForKey:key];
          NSLog(@"%@ = %@", key, value);
          *stop = YES;
      }
  }];
  
  // delete everything
  [mmkv clearAll];

• If different modules/logics need isolated storage, you can also create your own MMKV instance separately:

  MMKV *mmkv = [MMKV mmkvWithID:@"MyID"];
  [mmkv setBool:YES forKey:@"bool"];

• If multi-process accessing is needed(between the App and extensions)，you need to set the group directory on MMKV initialization as written before. Then you can get one by passing MMKVMultiProcess:

  MMKV *mmkv = [MMKV mmkvWithID:@"MyMultiID" mode:MMKVMultiProcess];
  [mmkv setBool:YES forKey:@"bool"];

Supported Types

• C/C++ Primitive Types：
  • bool, int32, int64, uint32, uint64, float, double
• Objective-C Class：
  • NSString, NSData, NSDate
• Any Class that implements <NSCoding> protocol.

Import from NSUserDefaults

• MMKV provides -[MMKV migrateFromUserDefaults:]，you can migrate from NSUserDefaults with one line of code.

  auto userDefault = [[NSUserDefaults alloc] initWithSuiteName:@"myDefault"];
  auto mmkv = [MMKV mmkvWithID:@"testImportNSUserDefaults"];
  [mmkv migrateFromUserDefaults:userDefault];
  // delete keys & values from userDefault when you're done

What's Next

• iOS in Advance
• iOS Performence