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;
}