用mailCode写邮箱客户端时出问题

用mailCode写了一个邮箱客户端，写了如下代码：

CTCoreAccount *account = [[CTCoreAccount alloc] init];
CTCoreFolder *folder;
BOOL success=[account connectToServer:@"imap.qq.com" port:143 connectionType:CONNECTION_TYPE_PLAIN authType:IMAP_AUTH_TYPE_PLAIN login:@"1029418889@qq.com" password:@"****"];
if(!success){
    NSLog(@"error");
}

folder = [account folderWithPath:@"INBOX"];
for (CTCoreMessage *msg in [folder messageObjectsFromIndex:0 toIndex:10]) {
       NSLog(@"%@" , msg.subject);
}

运行之后就会提示：
`
In the for{} block messageObjectsFromIndex:toIndex not found!
`

是不是这个方法没在MailCode中？