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[英]Looking for an explanation on why this C++ code does not work without references
[英]looking for explanation for a part of a code
我有由id代表的學生要在特定學期添加課程的功能。 這段代碼是正確的,但是當他這樣做時,我不理解該部分
for (size_t i = 0; i < (*iteratorVectorP).size(); i++) ...
void add_course(map<int, map<int, vector<course *> * > > &DB, int
semester, int id, course c)
{
auto iterator = DB.find(id); //find id as key, set map to value
vector<course*> *pointer = new vector<course*>;
if (iterator != DB.end())
{
auto iterator1 = ((*iterator).second).find(semester); //find
semester as key, set vector to value
if (iterator1 == (*iterator).second.end()) //if semester does not exist
{
pointer->push_back(new course(c));
(iterator->second)[semester] = pointer;
}
else //if semester exist
{
auto iteratorVectorP = (iterator->second)[semester];
// i do not understand what his doing here
for (size_t i = 0; i < (*iteratorVectorP).size(); i++)
{
if (c == *(*iteratorVectorP)[i])
{
return; //exit when class exist
}
else
{
(*iteratorVectorP).push_back(new course(c));
return;
}
}
}
}
}
iteratorVectorP的定義是向量,因此for循環正在迭代該過程,並嘗試將其添加到向量中(如果不存在)。
看起來iteratorVectorP是一個指針,因此調用(* iteratorVectorP).size()將獲得其指向的值。
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