blocks|key|3064281|text|有一个非常重要的技术原因：moc不能处理模板，这对于泛型容器类型来说是非常必要的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3064282|entityMap^0|D|3|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

There is a very important technical reason: The <code>moc</code> cannot handle templates, which is pretty much a necessity for a generic container type.

blocks|key|748313|text|QList应该是一种值类型(如std::vector)，它使用隐式共享，而QObjects必须用作指针，不允许复制|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|748314|还有其他类反映了这种用法，比如QImage|748315|entityMap^0|F|B|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

QList is meant to be a value type (like <code>std::vector</code>) which uses implicit sharing while QObjects must be used as pointers and disallow copying

there are other classes which mirror this use such as QImage

blocks|key|3064353|text|原因很简单，容器就像值一样，你有赋值运算符，你可以复制它们，克隆它们，等等。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3064354|QObject%25s不能具有此类功能，它们是不可复制的。试着想象一下，当你用连接的插槽和信号创建对象的克隆时会发生什么。这将导致彻底的混乱。克隆对象的子代应该发生什么呢？也应该被克隆吗？|offset|length|style|CODE|3064355|另一件事是模板的使用。类模板是一个QObject，它对于moc工具来说是一个真正问题。|3064356|entityMap^0|0|0|7|0|H|7|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@$D|Q|E|R|F|G]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|K|$]]

Reason is simple containers are like values, you have assign operator, you can copy them clone and so on. 

<code>QObject</code>s can't have such functionality, they are not copyable. Try imagine what should happen when you creating clone of object with connected slots and signals. It will lead to total mess. And what should happen with children of cloned object? Should be also cloned?

Another thing is templates usage. Class template which is a <code>QObject</code> is real problem for moc a tool.

blocks|key|3064383|text|你必须是QObject才能发出信号，这肯定不是真的。您所需要的就是在某个地方有一个QObject，它会为您发出信号。如果您希望您的类可以直接传递到QObject::connect，则您的类应该提供一个到QObject*的转换操作符，该操作符返回指向此类代理对象的指针。这完全回避了所有无模板和moc的喧嚣。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3064384|class+FrobinatorObject+:+public+QObject+{
++Q_OBJECT
++Q_SIGNAL+void+frobSignal();
++...
};

template+<typename+T>+class+Frobinator+{
++QScopedPointer<FrobinatorObject>+m_proxy;
++//+Could+be+a+QSharedPointer,+depending+on+what+semantics+we+want
++...
public:
++operator+FrobinatorObject*()+const+{+return+m_proxy.data();+}
};

++...
++Frobinator<int>+frob;
++QObject::connect(frob,+SIGNAL(frobSignal()),+...);
++//+or
++QObject::connect(frob,+&FrobinatorObject::frobSignal,+...);|code-block|syntax|javascript|3064385|还要注意的是，虽然在模板参数化的类中不能有信号或槽，但你肯定可以在基类中有它们，然后从基类派生。基类可以处理删除类型的参数。所以：|3064386|//+This+won't+work
template+<typename+T>+class+TemplateClass+:+public+QObject+{
++Q_OBJECT
++Q_SLOT+void+aSlot(const+T+*);
++...
};

//+But+this+certainly+does+work

class+BaseClass+:+public+QObject+{
++Q_OBJECT
++Q_SLOT+void+aSlot(const+void+*);
++...
}

template+<typename+T>+class+TemplateClass+:+public+BaseClass+{
++void+aMethod(const+T+*+t)+{
++++BaseClass::aSlot((const+void*)&t);
++}
++...
}|3064387|TemplateClass还可以动态地向BaseClass添加正确类型签名的槽。虽然这需要对Qt的内部结构有一定的了解，但对于一个应该是可重用的、框架样式的类来说，这当然是可以做到的。|3064388|entityMap^0|4|7|15|7|21|G|2T|8|0|0|0|0|0|D|K|9|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|R|$]]

It is certainly not true that you need to be a <code>QObject</code> to emit signals. All you need is there to be a <code>QObject</code> somewhere that emits the signals for you. If you want your class to be directly passable to <code>QObject::connect</code>, your class should provide a conversion operator to <code>QObject*</code> that returns the pointer to such a proxy object. This completely sidesteps the whole no-templates-with-moc brouhaha.

<pre><code>class FrobinatorObject : public QObject {
 Q_OBJECT
 Q_SIGNAL void frobSignal();
 ...
};

template &lt;typename T&gt; class Frobinator {
 QScopedPointer&lt;FrobinatorObject&gt; m_proxy;
 // Could be a QSharedPointer, depending on what semantics we want
 ...
public:
 operator FrobinatorObject*() const { return m_proxy.data(); }
};

 ...
 Frobinator&lt;int&gt; frob;
 QObject::connect(frob, SIGNAL(frobSignal()), ...);
 // or
 QObject::connect(frob, &amp;FrobinatorObject::frobSignal, ...);
</code></pre>

Also note that while it's true that you can't have signals nor slots in a template-parametrized class, you can certainly have them in a base class that you then derive from. The base class can deal with type-deleted arguments. So:

<pre><code>// This won't work
template &lt;typename T&gt; class TemplateClass : public QObject {
 Q_OBJECT
 Q_SLOT void aSlot(const T *);
 ...
};

// But this certainly does work

class BaseClass : public QObject {
 Q_OBJECT
 Q_SLOT void aSlot(const void *);
 ...
}

template &lt;typename T&gt; class TemplateClass : public BaseClass {
 void aMethod(const T * t) {
 BaseClass::aSlot((const void*)&amp;t);
 }
 ...
}
</code></pre>

The <code>TemplateClass</code> can also dynamically add slots of the correct type signature to the <code>BaseClass</code>. While that requires some understanding of Qt's internals, it can certainly be done for a class that's supposed to be a reusable, framework-style class.

blocks|key|969184|text|虽然我不能了解开发人员的想法，但我会说根本没有必要。QList是一个简单的容器。它应该包含元素，允许添加或删除元素，在元素上迭代，等等。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|969185|它不需要父级或子级。不需要立即使用信号或插槽。这是让事情变得简单的问题。|969186|如果除了QList提供的功能之外，您确实需要其他功能，那么实现它就足够容易了。但对于一般情况，我想这是一个合理和合乎逻辑的决定，不要把事情搞得过于复杂。|969187|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

While I can't look into the minds of the developers, I would say that there's simply no need. A QList is a simple container. It should hold elements, allow for their addition or removal, iteration over them, etc. 

It does not need a parent or children. There's no immediate need for signals or slots. It's a matter of keeping things simple. 

If you do indeed require additional functionality beyond what a QList provides, it's easy enough to implement. But as for a general case, I guess it's a reasonable and logical decision to not overcomplicate things.

blocks|key|975449|text|在大多数情况下，从QObject继承的额外开销是不必要的。容器应该尽可能的小和快。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|975450|如果您想从QList继承并为您自己的类提供该功能，您可以这样做。|975451|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

The extra overhead in inheriting from QObject is unnecessary for the majority of uses. Containers should be as small and as fast as possible.

If you wanted to inherit from QList and provide that functionality for a class of your own, you can do that.

I wanted to create a <code>QObservableCollection</code> wrapper around a <code>QList</code>(using an internal <code>QList</code> for implementation and forwarding all calls while emiting some sort of CollectionsChanged signal for functions that change the collection), but I see that <code>QList</code> does not inherit from <code>QObject</code>.

I believe you need to inherit from <code>QObject</code> to emit Qt Signals. So I'd need to inherit from <code>QObject</code> for my QObeservableCollection.

But <code>QList</code> and <code>QVector</code> and the other Qt collections doen't inherit from <code>QObject</code>, so I imagine their must be some sort of downside or problem making a collection.

I see that QSignalSpy inherits from both <code>QObject</code> and <code>QList&lt;QList&lt;QVariant&gt;&gt;</code> so maybe they just didn't see a reason to inherit from QObject?

Why is a QList not derived from a QObject?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想在QList周围创建一个QObservableCollection包装器(使用内部QList实现并转发所有调用，同时为更改集合的函数发出某种CollectionsChanged信号)，但我发现QList不是从QObject继承的。我相信你需要继承QObject才能发出Qt信号。所以我的QObeservableCollection需要从QObject继承。但是QList和QVector以及其他Q

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