Question

我正在尝试创建一个唯一且具有主键的表。我知道在sqlite中我们可以开发唯一的AUTOINCREMENT ID SQL AUTOINCREMENT，但是可以生成36个字符长的唯一GUID。这样做的唯一原因是使其更加独特。

Answer 1

这是我用于UUID的代码（我甚至可能在Stack Overflow上找到它）......

+ (NSString *)GetUUID
{
    CFUUIDRef theUUID = CFUUIDCreate(NULL);
    CFStringRef string = CFUUIDCreateString(NULL, theUUID);
    CFRelease(theUUID);
    return [(NSString *)string autorelease];
}

我不知道UUID生成的时间有多长，因为在我使用它的方式中我并不关心，所以也许通过将结果传递给NSLog来检查它。

HTH，佩德罗：）

Answer 2

我使用此代码在iphone上生成guid - NSString上的类别。不记得我发现它的位置，但效果很好。

#import "NSString_UniqueID.h"


static unichar x (unsigned int); 

@implementation NSString (TWUUID) 

+ (NSString*) stringWithUniqueId 
{ 
    CFUUIDRef uuid = CFUUIDCreate(NULL); 
    CFUUIDBytes b = CFUUIDGetUUIDBytes(uuid); 
    unichar unichars[22]; 
    unichar* c = unichars; 
    *c++ = x(b.byte0 >> 2); 
    *c++ = x((b.byte0 & 3 << 4) + (b.byte1 >> 4)); 
    *c++ = x((b.byte1 & 15 << 2) + (b.byte2 >> 6)); 
    *c++ = x(b.byte2 & 63); 
    *c++ = x(b.byte3 >> 2); 
    *c++ = x((b.byte3 & 3 << 4) + (b.byte4 >> 4)); 
    *c++ = x((b.byte4 & 15 << 2) + (b.byte5 >> 6)); 
    *c++ = x(b.byte5 & 63); 
    *c++ = x(b.byte6 >> 2); 
    *c++ = x((b.byte6 & 3 << 4) + (b.byte7 >> 4)); 
    *c++ = x((b.byte7 & 15 << 2) + (b.byte8 >> 6)); 
    *c++ = x(b.byte8 & 63); 
    *c++ = x(b.byte9 >> 2); 
    *c++ = x((b.byte9 & 3 << 4) + (b.byte10 >> 4)); 
    *c++ = x((b.byte10 & 15 << 2) + (b.byte11 >> 6)); 
    *c++ = x(b.byte11 & 63); 
    *c++ = x(b.byte12 >> 2); 
    *c++ = x((b.byte12 & 3 << 4) + (b.byte13 >> 4)); 
    *c++ = x((b.byte13 & 15 << 2) + (b.byte14 >> 6)); 
    *c++ = x(b.byte14 & 63); 
    *c++ = x(b.byte15 >> 2); 
    *c = x(b.byte15 & 3); 
    CFRelease(uuid); 
    return [NSString stringWithCharacters: unichars length: 22]; 
} 
@end 
// Convert six-bit values into letters, numbers or _ or $ (64 characters in that set). 
//------------------------------------------------------------------------------------ 
unichar x (unsigned int c) 
{ 
    if (c < 26) return 'a' + c; 
    if (c < 52) return 'A' + c - 26; 
    if (c < 62) return '0' + c - 52; 
    if (c == 62) return '$'; 
    return '_'; 
}

如何在SQLITE iPhone中生成唯一的GUID 36字符

2 个答案: