QVariant 内部如何工作？
我想知道，QVariant 如何在内部存储 int、QMap、QList...
我的意思是内部数据结构/实现是什么？在 QVariant 中存储和检索类型（int、float）的开销是多少？
I want to know, How QVariant can internally stores, int, QMap, QList,...
I mean what is the internal data-structure/Implementation? What is the overhead of storing and retrieving types (int, float) in QVariant?
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快速浏览一下代码就会发现，
QVariant基本上是几个基本类型（int、float）的联合等），一个 QObject 指针，以及一个用于非QObject和非原语的任何其他内容的void*指针。还有一个类型数据成员，允许它知道当前实际存储的内容。开销似乎并不比存储到结构体的成员、检查类型兼容性并可能进行转换（例如 int 到 float）多多少A quick look at the code reveals that a
QVariantis basically aunionof several primitive types (int,floatetc'), aQObjectpointer, and avoid*pointer for anything else that is not aQObjectand not a primitive. There is also a type data member that allows it to know what's actually currently stored there. The overhead appears to be not much more than storing to a member of a struct, checking that for type compatibility and possibly making a conversion (int to float for instance)