C++ - 读取字符串字符时出错
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-Error reading characters of string
提问by Victor
I have the following block of code:
我有以下代码块：
for( CarsPool::CarRecord &record : recs->GetRecords())
{
LVITEM item;
item.mask = LVIF_TEXT;
item.cchTextMax = 6;
item.iSubItem = 0;
item.pszText = (LPSTR)(record.getCarName().c_str()); //breakpoint on this line.
item.iItem = 0;
ListView_InsertItem(CarsListView, &item);
item.iSubItem = 1;
item.pszText = TEXT("Available");
ListView_SetItem(CarsListView, &item);
item.iSubItem = 2;
item.pszText = (LPSTR)CarsPool::EncodeCarType(record.getCarType());
ListView_SetItem(CarsListView, &item);
}
The information from Visual Studio Debugger is here:
Visual Studio Debugger 的信息在这里：
Why isn't the program able to read the characters from string?
为什么程序不能从字符串中读取字符？
A test has shown me that it works in this way:
一个测试告诉我它是这样工作的：
MessageBox(hWnd, (LPSTR)(record.getCarName().c_str()), "Test", MB_OK);
采纳答案by IInspectable
getCarNamelikely returns a temporary. After the assignment the temporary object is destroyed and the pointer item.pszTextpoints to invalid memory. You must ensure that the string object is valid during the call to ListView_InsertItem.
getCarName可能返回一个临时的。赋值后临时对象被销毁，指针item.pszText指向无效内存。您必须确保字符串对象在调用 期间有效ListView_InsertItem。
std::string text(record.getCarName());
item.iSubItem = 0;
item.pszText = const_cast<LPSTR>(text.c_str());
item.iItem = 0;
ListView_InsertItem(CarsListView, &item);
The const_castis an artifact of the fact that the Windows API uses the same structure to set and retrieve information. When invoking ListView_InsertItemthe structure is immutable, however there is no way to reflect that in the language.
这const_cast是 Windows API 使用相同结构来设置和检索信息这一事实的产物。当调用ListView_InsertItem结构是不可变的，但是没有办法在语言中反映出来。
回答by paulsm4
It looks like you're trying to use the value of a C++ "string" in a C/Win32 call.
看起来您正在尝试在 C/Win32 调用中使用 C++“字符串”的值。
stdstring.c_str() is the correct way to do it.
stdstring.c_str() 是正确的方法。
... BUT ...
... 但 ...
You should strcpy() the string to a temp variable, then make the Win32 call with the temp variable.
您应该将字符串 strcpy() 转换为临时变量，然后使用临时变量进行 Win32 调用。
