本文主要是提供MMKV的代码使用教程，若是想知道更多关于MMKV的信息，能够点击如下连接，查看更多信息：html

2. MMKV浅析github

MMKV实际使用的代码案例以下：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

// Override point for customization after application launch.

[MMKV setLogLevel:MMKVLogNone];//关闭MMKV控制台打印的自带的辅助日志信息

[self kvCreateMethod];//建立MMKV的方法

[self compareMMKVWithNSUesrDefault];//比较MMKV和NSUserDefaults存储数据的效率

[self cLanguageDataType];//存储和读取C语言数据类型

[self ocLanguageDataType];//存储和读取OC语言数据类型

[self kvMigrateFromUserDefaults];//从NSUserDefaults迁移数据到MMKV

// [[MMKV defaultMMKV] clearAll];

//totalSize:文件分配的总磁盘空间4k；actualSize：存储文件占据的实际存储空间298byte

NSLog(@"count:%zu-----totalSize:%zu------actualSize:%zu-----allKeys:%@",[[MMKV defaultMMKV] count],

[[MMKV defaultMMKV] totalSize],[[MMKV defaultMMKV] actualSize],[[MMKV defaultMMKV] allKeys]);

//打印结果：count:7-----totalSize:4096------actualSize:298-----allKeys:(double,uint64,uint32,int32,bool,int64,float)

return YES;

}复制代码

建立MMKV的方法：ide

/*

//如下四种建立方法是彻底等价的,建立的是同一个MMKV实例

*/

- (void)kvCreateMethod

{

//MMKV文件存储的默认为~/Documents/mmkv

NSString *basePath = [MMKV mmkvBasePath];

//修改文件存储的默认路径，在建立MMKV实例以前设置

[MMKV setMMKVBasePath:@""];

//第一种建立方法

MMKV *defaultKV1 = [MMKV defaultMMKV];

//第二种建立方法

MMKV *defaultKV3 = [MMKV mmkvWithID:@"mmkv.default"];

//第三种建立方法

NSString *string = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];

string = [string stringByAppendingPathComponent:@"mmkv"];

MMKV *defaultKV4 = [MMKV mmkvWithID:@"mmkv.default" relativePath:string];

//第四种建立方法

MMKV *defaultKV2 = [MMKV mmkvWithID:@"mmkv.default" cryptKey:nil relativePath:string];

}复制代码

比较MMKV和NSUserDefaults存储数据的效率：

ui

/*

写入10万个数据所用的时间

MMKV : 198.487043ms

NSUserDefaults : 13829.244971ms

*/

- (void)compareMMKVWithNSUesrDefault

{

CFAbsoluteTime startTime =CFAbsoluteTimeGetCurrent();

MMKV *customKV = [MMKV mmkvWithID:@"cn.meicai"];

for (int i=0; i<100000; i++) {

[customKV setInt32:i forKey:@"int32"];

}

CFAbsoluteTime linkTime = (CFAbsoluteTimeGetCurrent() - startTime);

NSLog(@"Linked in %f ms", linkTime *1000.0);

NSLog(@"------%d--------",[customKV getInt32ForKey:@"int32"]);

// CFAbsoluteTime startTime =CFAbsoluteTimeGetCurrent();

// NSUserDefaults *userDefault = [NSUserDefaults standardUserDefaults];

// for (int i=0; i<100000; i++) {

// [userDefault setInteger:i forKey:@"int32"];

// }

// CFAbsoluteTime linkTime = (CFAbsoluteTimeGetCurrent() - startTime);

// NSLog(@"Linked in %f ms", linkTime *1000.0);

// NSLog(@"------%ld--------",(long)[userDefault integerForKey:@"int32"]);

}

复制代码

存储和读取C语言数据类型：

加密

/*

//支持如下 C 语语言基础类型：

//bool、int3二、int6四、uint3二、uint6四、float、double

*/

- (void)cLanguageDataType

{

MMKV *mmkv = [MMKV defaultMMKV];

[mmkv setBool:YES forKey:@"bool"];

NSLog(@"bool:%d", [mmkv getBoolForKey:@"bool"]);//打印结果：bool:1

[mmkv setInt32:-1024 forKey:@"int32"];

NSLog(@"int32:%d", [mmkv getInt32ForKey:@"int32"]);//打印结果：int32:-1024

[mmkv setUInt32:std::numeric_limits::max() forKey:@"uint32"];

NSLog(@"uint32:%u", [mmkv getUInt32ForKey:@"uint32"]);//打印结果：uint32:4294967295

[mmkv setInt64:std::numeric_limits::min() forKey:@"int64"];

NSLog(@"int64:%lld", [mmkv getInt64ForKey:@"int64"]);//打印结果：int64:-9223372036854775808

[mmkv setUInt64:std::numeric_limits::max() forKey:@"uint64"];

NSLog(@"uint64:%llu", [mmkv getInt64ForKey:@"uint64"]);//打印结果：uint64:18446744073709551615

[mmkv setFloat:-3.1415926 forKey:@"float"];

NSLog(@"float:%f", [mmkv getFloatForKey:@"float"]);//打印结果：float:-3.141593

[mmkv setDouble:std::numeric_limits::max() forKey:@"double"];

NSLog(@"double:%f", [mmkv getDoubleForKey:@"double"]);//打印结果：double:17976931348......24858368.000000

}复制代码

存储和读取OC语言数据类型：

spa

/*

支持如下 ObjC 类型：

NSString、NSData、NSDate

*/

- (void)ocLanguageDataType

{

//cryptKey 根据此秘钥建立AES加密器,加密后的数据存取方法不变，和未加密的同样

MMKV *mmkv = [MMKV mmkvWithID:@"cn.meicai" cryptKey:[@"crypt" dataUsingEncoding:NSUTF8StringEncoding]];

[mmkv setString:@"hello, mmkv" forKey:@"string"];

NSLog(@"string:%@ defaultValue:%@", [mmkv getStringForKey:@"string"],[mmkv getStringForKey:@"string111" defaultValue:@"mmmmmmmmmmmmmmmm"]);

//打印结果:string:hello, mmkv defaultValue:mmmmmmmmmmmmmmmm

[mmkv setObject:nil forKey:@"string"];

NSLog(@"string after set nil:%@, containsKey:%d",

[mmkv getObjectOfClass:NSString.class

forKey:@"string"],

[mmkv containsKey:@"string"]);

//打印结果:string after set nil:(null), containsKey:0

[mmkv setDate:[NSDate date] forKey:@"date"];

NSLog(@"date:%@ defaultValue:%@", [mmkv getDateForKey:@"date"],[mmkv getDateForKey:@"date111" defaultValue:[NSDate date]]);

//打印结果:date:Wed Jun 26 14:39:52 2019 defaultValue:Wed Jun 26 14:39:52 2019

[mmkv setData:[@"hello, mmkv again and again" dataUsingEncoding:NSUTF8StringEncoding] forKey:@"data"];

NSData *data = [mmkv getDataForKey:@"data"];

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

//打印结果:data:hello, mmkv again and again

}复制代码

从NSUserDefaults迁移数据到MMKV：

/*

从NSUserDefault迁移数据到MMKV的实例

*/

- (void)kvMigrateFromUserDefaults

{

[[NSUserDefaults standardUserDefaults] setObject:@"hello world" forKey:@"string"];

[[NSUserDefaults standardUserDefaults] synchronize];

MMKV *userDefaultKV = [MMKV mmkvWithID:@"NSUserDefault"];

[userDefaultKV migrateFromUserDefaults:[NSUserDefaults standardUserDefaults]];

[userDefaultKV enumerateKeys:^(NSString * _Nonnull key, BOOL * _Nonnull stop) {

if ([key isEqualToString:@"string"]) {

NSLog(@"string value is : %@",[userDefaultKV getStringForKey:key]);//打印结果：string value is : hello world

NSLog(@"string value is : %@",[userDefaultKV getObjectOfClass:[NSString class] forKey:key]);//打印结果：string value is : hello world

NSLog(@"string value is : %@",[userDefaultKV getObjectOfClass:[NSNumber class] forKey:key]);//打印结果：string value is : (null)

*stop = YES;

}

}];

}复制代码