IOS 随机字符串

- (NSString*) randomString:(int)len {

    char* charSet ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

    char* temp =malloc(12 +1);

    for (int i =0; i < 12; i++) {

        int randomPoz =arc4random()%strlen(charSet);

        temp[i] = charSet[randomPoz];

    }

    temp[len] = '\0';

    NSMutableString* randomString = [[NSMutableStringalloc] initWithUTF8String:temp];

    free(temp);

    return randomString;

}