iOS官方文档 Foundation篇---Unique Identifiers

NSUUID

UUID（通用唯一标识符），也称为GUID（全局唯一标识符）或IID（接口标识符），是128位值。通过NSUUID符合RFC 4122版本4 创建的UUID，使用随机字节创建。

创建UUID

//使用RFC 4122版本4随机字节创建并返回新的UUID
+ (instancetype)UUID;

//使用RFC 4122版本4随机字节初始化新的UUID
- (instancetype)init;

//使用格式化字符串初始化新UUID(string不符合UUID标准则返回nil)
- (nullable instancetype)initWithUUIDString:(NSString *)string;

//使用给定的字节初始化新的UUID
- (instancetype)initWithUUIDBytes:(const uuid_t _Nullable)bytes;

//以字节形式返回UUID
- (void)getUUIDBytes:(uuid_t _Nonnull)uuid;

//UUID字符串
@property (readonly, copy) NSString *UUIDString;

NSString *uuid = [[NSUUID UUID]UUIDString];//46B7A198-81A5-4B90-88BD-270BDBBC1A30
NSUUID *uuid = [NSUUID UUID];//FFCA4124-DDDF-4E11-AC52-7C05357757E3

NSUUID *uuid = [[NSUUID alloc]initWithUUIDString:@"uuid"];//nil
NSUUID *uuid = [[NSUUID alloc]initWithUUIDString:@"68753A44-4D6F-1226-9C60-0050E4C00067"];//68753A44-4D6F-1226-9C60-0050E4C00067

NSString *str = @"qwerty";
NSData *dataStr = [str dataUsingEncoding:NSUTF8StringEncoding];
Byte *byte = (Byte *)[dataStr bytes];
NSString *uuid = [[NSUUID alloc] initWithUUIDBytes:byte].UUIDString;//68753A44-4D6F-1226-9C60-0050E4C00067

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