机器适配？？

- (BOOL)nicePerformance{    size_t size;    sysctlbyname("hw.machine", NULL, &size, NULL, 0);    char *name = malloc(size);    sysctlbyname("hw.machine", name, &size, NULL, 0);    NSString *machine = [NSString stringWithCString:name encoding:NSUTF8StringEncoding];    free(name);    BOOL b = YES;    if ([machine hasPrefix:@"iPhone"]) {        b = [[machine substringWithRange:NSMakeRange(6, 1)] intValue] >= 4;    }else if ([machine hasPrefix:@"iPod"]){        b = [[machine substringWithRange:NSMakeRange(4, 1)] intValue] >= 5;    }else if ([machine hasPrefix:@"iPad"]){        b = [[machine substringWithRange:NSMakeRange(4, 1)] intValue] >= 2;    }    return b;}