需要有关std :: list的帮助 [英] Need help regarding std::list
问题描述
好的，在我的程序中我有一个std :: list< Document *>，其中Document是我自己的一个
自己的类之一。
我需要查看此列表并检查每个项目是否已准备好删除
。如果不是，请跳到下一步，如果已经准备好，我会采取措施删除
。问题是列表是gui应用程序的一部分，系统
在执行循环体时从列表中删除Document *。
这意味着我不能使用迭代器迭代列表。所以我尝试使用
列表的大小，如下所示：
while（m_documents.size（））
{
文件* ptr = m_documents.front（）;
if（ptr-> ready_for_deletion（））
{
ptr-> clean_up（）; //这会在下一步之前从列表中删除ptr
迭代
}
}
这个解决方案的问题是我得到了一个无限循环的文件
还没准备好删除。我需要确定我是否已经询问了文件是否已经准备好删除，并且在所有文件被删除之前循环或
只有列表中留下的非就绪文件。我想不出一个
的解决方案。我可以创建一个只有文件准备删除的新列表，然后
然后删除那些，但这不是一个选项，因为当我找到一个
文件准备好了删除，我需要立即将其删除，而不是稍后。
不确定我是否有意义，也许我不在话题。如果有的话，我道歉。
/ WP
William Payne写道：好的，在我的程序中我有一个std :: list< Document *>，其中Document是我自己的类之一。
我需要查看这个列表并且检查每个项目是否已准备好删除
。如果不是，请跳到下一步，如果已经准备就绪，我会采取措施删除它。问题是列表是gui应用程序的一部分，系统在执行循环体时从列表中删除Document *。
这意味着我不能使用迭代器迭代列表。
是的，你可以。
for（std :: list< Document *> :: iterator it = doclist.begin（） ;
it！= doclist.end（）;
）//注意：没有++它
{
Document * pd = * it;
if（pd-> ready_for_deletion（））
{
pd-> clean_up（ ）;
删除pd;
it = doclist.erase（it）;
}
else
++ it;
}
RTFM。
[...]
Victor
" Victor Bazarov" <五******** @ comAcast.net>在消息中写道
news：l6 **************** @ newsread1.dllstx09.us.to.v erio.net ...William Payne写道：好的，在我的程序中我有一个std :: list< Document *>，其中Document是我自己的类之一。
我需要查看此列表，并检查每个项目是否已准备好删除
。如果不是，请跳到下一步，如果已经准备就绪，我会采取措施删除它。问题是列表是gui应用程序的一部分，
系统在执行
循环体时从列表中删除Document *。这意味着我无法使用迭代器迭代列表。
是的，你可以。
for（std :: list< Document *> :: iterator it = doclist.begin（）;
it！= doclist.end（）;
）//注意：没有++它
{
文件* pd = *它;
if（pd-> ready_for_deletion（））
{
pd-> clean_up（）;
删除pd;
it = doclist.erase（it ）;
}
其他
++ it;
}
RTFM。
[.. 。]
Victor
感谢您快速回复，Victor。有趣的解决方案。不幸的是，
实际删除了ptr_document;被称为其他地方（在gui库的
约束下工作），但我会看到我能用你的解决方案做什么。
/ WP
William Payne写道：" Victor Bazarov" <五******** @ comAcast.net>在消息中写道
新闻：l6 **************** @ newsread1.dllstx09.us.to.v erio.net ...
William Payne写道：
好的，在我的程序中我有一个std :: list< Document *>，其中Document是我自己的类之一。
我需要查看此列表并检查每个项目是否已准备好删除
。如果不是，请跳到下一步，如果已经准备就绪，我会采取措施删除它。问题是列表是gui应用程序的一部分，
系统在执行
循环体时从列表中删除Document *。这意味着我无法使用迭代器迭代列表。
是的，你可以。
for（std :: list< Document *> :: iterator it = doclist.begin（）;
it！= doclist.end（）;
）//注意：没有++它
{
文件* pd = *它;
if（pd-> ready_for_deletion（））
{
pd-> clean_up（）;
删除pd;
it = doclist.erase（it ）;
}
++ it;
}
RTFM。
[...]
Victor
感谢您快速回复，Victor。有趣的解决方案。不幸的是，
实际删除了ptr_document;在其他地方被调用（在gui库的
约束下工作），但我会看到我可以用你的解决方案做什么。
你可以随时提取将要删除的列表元素分成
a单独列表，然后将其传递到其他地方进行处理。
Victor
Ok, in my program I have a std::list<Document*>, where Document is one of my
own classes.
I need to go through this list and check each item if it''s ready for
deletion. If it''s not, skip to next, if it''s ready I take steps to delete
it. The thing is that the list is part of a gui application and the system
removes the Document* from the list during the execution of the loop body.
That means I cant use iterators to iterate over the list. So I tried using
the size of the list, like this:
while(m_documents.size())
{
Document* ptr = m_documents.front();
if(ptr->ready_for_deletion())
{
ptr->clean_up(); // This removes ptr from the list before next
iteration
}
}
The problem with that solution is that I get an endless loop for Documents
not ready for deletion. I need to determine if I''ve asked a document if it''s
ready for deletion or not and loop until all documents have been deleted or
there are only non-ready documents left in the list. I can''t think of a
solution. I could create a new list of only Documents ready for deletion and
then delete those, but that''s not really an option because when I find a
document ready for deletion, I need to delete it right now, not a bit later.
Not sure I''m making much sense and maybe I''m off-topic. If so, I apologise.
/ WP
William Payne wrote:Ok, in my program I have a std::list<Document*>, where Document is one of my
own classes.
I need to go through this list and check each item if it''s ready for
deletion. If it''s not, skip to next, if it''s ready I take steps to delete
it. The thing is that the list is part of a gui application and the system
removes the Document* from the list during the execution of the loop body.
That means I cant use iterators to iterate over the list.
Yes, you can.
for (std::list<Document*>::iterator it = doclist.begin();
it != doclist.end();
) // note: no ++it
{
Document *pd = *it;
if (pd->ready_for_deletion())
{
pd->clean_up();
delete pd;
it = doclist.erase(it);
}
else
++it;
}
RTFM.
[...]
Victor
"Victor Bazarov" <v.********@comAcast.net> wrote in message
news:l6****************@newsread1.dllstx09.us.to.v erio.net...William Payne wrote:Ok, in my program I have a std::list<Document*>, where Document is one of
my own classes.
I need to go through this list and check each item if it''s ready for
deletion. If it''s not, skip to next, if it''s ready I take steps to delete
it. The thing is that the list is part of a gui application and the
system removes the Document* from the list during the execution of the
loop body. That means I cant use iterators to iterate over the list.
Yes, you can.
for (std::list<Document*>::iterator it = doclist.begin();
it != doclist.end();
) // note: no ++it
{
Document *pd = *it;
if (pd->ready_for_deletion())
{
pd->clean_up();
delete pd;
it = doclist.erase(it);
}
else
++it;
}
RTFM.[...]
Victor
Thanks for quick reply, Victor. Interesting solution. Unfortunately, the
actual delete ptr_document; is called somewhere else (working under the
constrains of gui library), but I will see what I can do with your solution.
/ WP
William Payne wrote:"Victor Bazarov" <v.********@comAcast.net> wrote in message
news:l6****************@newsread1.dllstx09.us.to.v erio.net...William Payne wrote:Ok, in my program I have a std::list<Document*>, where Document is one of
my own classes.
I need to go through this list and check each item if it''s ready for
deletion. If it''s not, skip to next, if it''s ready I take steps to delete
it. The thing is that the list is part of a gui application and the
system removes the Document* from the list during the execution of the
loop body. That means I cant use iterators to iterate over the list.
Yes, you can.
for (std::list<Document*>::iterator it = doclist.begin();
it != doclist.end();
) // note: no ++it
{
Document *pd = *it;
if (pd->ready_for_deletion())
{
pd->clean_up();
delete pd;
it = doclist.erase(it);
}
else
++it;
}
RTFM.[...]
Victor
Thanks for quick reply, Victor. Interesting solution. Unfortunately, the
actual delete ptr_document; is called somewhere else (working under the
constrains of gui library), but I will see what I can do with your solution.
You can always extract the elements of the list to be deleted into
a separate list and then pass it somewhere else to be disposed of.
Victor
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