blocks|key|187807|text|您应该删除应用程序的debug文件夹，然后重新运行它以更正此问题。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|187808|entityMap^0|A|5|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|$]]

You should delete the <code>debug</code> folder of your application and run it again to correct this problem.

blocks|key|187873|text|如果你使用的是Visual+Studio，从头文件中删除Q_OBJECT行，保存该文件，将Q_OBJECT放回到头文件中，然后再次保存该文件。这应该会生成moc_*文件，并且应该正确地构建和链接。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|187874|entityMap^0|S|8|19|8|25|5|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

If you're using Visual Studio, delete the line <code>Q_OBJECT</code> from the header file, save the file, put <code>Q_OBJECT</code> back into the header file, save the file again. This should generate the <code>moc_*</code> file and should build and link correctly.

blocks|key|405956|text|所以问题是我需要Qt编译器来编译我的.h文件。这对于任何扩展QObject或其子类的类都是必需的。修复涉及到(对我来说)右键单击头文件，选择属性，将项类型设置为"Qt输入“，然后在头文件上点击”编译“，然后将生成的moc_myfilename.cpp文件添加到我的项目中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|405957|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

So the issue was I needed the Qt MOC compiler to compile my .h file. This is required for any classes that extend QObject or one of its children. The fix involed (for me) right-clicking on the header file, choosing Properties, and setting the Item Type to "Qt MOC Input", then hitting "Compile" on the header, and then adding the resulting moc_myfilename.cpp file to my project.

blocks|key|188120|text|如果moc文件是在visual+studio项目中生成的，请尝试将它们包含在项目中，如果它们未包含在项目中，则重新生成。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|188121|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If your moc files are generated in the visual studio project try to include them into project if they are not included into project then rebuild.

blocks|key|406401|text|当我的cpp文件中有一个Q_OBJECT类定义时，我在Visual+Studio2012中遇到了这个问题。将类定义移动到头文件解决了此问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|406402|看起来应该可以通过将cpp文件添加到moc来支持cpp文件中的Q_OBJECT类，但我没有尝试这样做。|406403|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|$]]

I had this problem with Visual Studio 2012 when I had a Q_OBJECT class definition in my cpp file. Moving the class definition to the header file resolved the issue.

It looks like it should be possible to support Q_OBJECT class in cpp file by adding the cpp file to moc but I did not try this.

blocks|key|406150|text|我使用CMake来管理Qt项目，并且需要在QT4_WRAP_CPP调用下添加新的Q_OBJECT。这将生成包含在项目中的moc_*.cxx，并清理未解析的外部变量。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|406151|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I use CMake to manage Qt projects and the new Q_OBJECT needs to be added under the QT4_WRAP_CPP call. This will generate the moc_*.cxx for inclusion in the project and clean up the unresolved externals.

blocks|key|188387|text|在链式CMake目标的情况下遇到了这个问题。结果，我不得不启用CMAKE_AUTOMOC，即使在没有直接(传递)使用Qt的目标中也是如此。也证明了CMAKE_AUTOMOC不能在父级的相同CMakeLists.txt或CMakeLists.txt中使用没有find_package(QtX)的情况。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|188388|entityMap^0|V|D|21|D|2M|E|31|E|3K|H|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|G|$]]

Faced this issue in case of chained CMake targets. Turned out I had to enable <code>CMAKE_AUTOMOC</code> even in targets that didn't use Qt directly (transitively). Also turned out that <code>CMAKE_AUTOMOC</code> can't be used w/o <code>find_package(QtX)</code> in same <code>CMakeLists.txt</code> or <code>CMakeLists.txt</code> of parent.

blocks|key|406063|text|在我的例子中(在VS2012和Qtv4.8.4中使用QtAdd-in+)上述建议都不起作用。由于某些原因，VS无法生成正确的moc文件(构建输出:找不到相关的类。未生成任何输出。)当我手动编译相关的头文件时(将qt+moc设置为编译器并点击‘编译’)，它产生了空的moc文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|406064|真正起作用的是从命令行(moc、-o、moc_SomeClass.cpp、SomeClass.h)编译所有必要的moc，然后替换GeneratedFiles文件夹中错误的moc。|406065|这只是一个让你的项目成功构建的变通方法(对于一个大项目来说并不方便)，但并不能真正解释奇怪的VS/QtAdd-in行为。|406066|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|$]]

In my case (using QtAdd-in with VS2012 and Qt v4.8.4) none of the above suggestions worked.
For some reason VS could not generate proper moc files (build output: No relevant classes found. No output generated.) and when I compiled relevant headers by hand (setting qt moc as a compiler and clicking 'Compile') it produced empty moc file. 

What did work was to compile all necessary mocs from command line (moc -o moc_SomeClass.cpp SomeClass.h) and then replace the wrong ones in GeneratedFiles folder.

This is only workaround (and not a convenient one for a big project) to have your project build succesfully, but does not really explain strange VS/QtAdd-in behaviour.

blocks|key|406187|text|使用QtAdd-in和VS2010，我意识到moc_*.cpp文件在GeneratedFiles/Debug文件夹中被更新了，尽管我处于发布模式。将文件复制到Release文件夹中对我来说很有效。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|406188|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Using QtAdd-in with VS2010 i realized the moc_*.cpp files were updated in the GeneratedFiles/Debug folder although i was in release mode. Copying the files into the Release folder worked for me.

blocks|key|188074|text|这发生在我最近从MingW切换到MSVC的时候。我有一个原型化的类/结构被列为一个类，而MingW并不介意。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|188075|当涉及到原型设计时，MSVC肯定看到了class和struct之间的区别。|offset|length|style|CODE|188076|希望有一天能帮助到别人。|188077|entityMap^0|0|J|5|P|6|0|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]|$D|P|E|Q|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|R|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|K|$]]

This happened to me recently when switching from MingW to MSVC. I had a prototyped class/struct listed as a class, and MingW didn't mind.

MSVC definitely sees a difference between <code>class</code> and <code>struct</code> when prototyping is concerned.

Hope that helps someone else one day.

blocks|key|188169|text|在我的例子中，上述方法都不起作用，但这完全是我的错误。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|188170|我在.h文件中覆盖了虚函数(声明了它们)，但从未在.cpp中定义过它们:)|188171|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|$]]

In my case, none of the above worked but it was totally my mistake.

I had overrided virtual functions in .h file (declared them) but had never defined them in .cpp :)

blocks|key|188197|text|我通过将以下内容添加到我的头文件中解决了我的问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|188198|#ifndef+MYCLASSNAME_H
#define+MYCLASSNAME_H

...+//+all+the+header+file+content.

#endif|code-block|syntax|javascript|188199|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I solved my problem by adding this to my header file :

<pre><code>#ifndef MYCLASSNAME_H
#define MYCLASSNAME_H

... // all the header file content.

#endif
</code></pre>

blocks|key|406429|text|我正在使用集成的Perforce+p4v客户端在VS2015中工作。在我的例子中，Perforce试图将moc文件添加到一个depo中，当我恢复这个操作时，Perforce从项目中删除了这个moc文件并删除了它。该文件是在下一次编译后重新创建的，但它没有包含在项目中，当我最终了解问题所在时，我必须手动将其添加到生成的文件中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|406430|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I am working in VS2015 with an integrated Perforce p4v client.
In my case Perforce tried to add moc file to a depo, when I reverted this operation, Perforce removed this moc file from project and deleted it.
The file was recreated after the next compilation, but it wasn't included in project, I have to add it manually to Generated files, when I finally understood what was the problem.

blocks|key|188301|text|我有同样的问题，我的解决方案是编码(我的文件与“ASCII”不能生成与moc.exe+)，y创建另一个文件与UTF16LE编码，它的工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|188302|HxD+HexEditor可以帮助您查看代码。|188303|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|$]]

I have the same problem, my solution was the encoding( my file with "UTF16LE BOM" can't generate with moc.exe ) , y create another file with ASCII enconding and it work.

HxD HexEditor can help you to see the codification.

blocks|key|406471|text|我知道这是一个非常古老的问题，但它似乎仍然很有趣(在过去的几个月里，我至少来过这里4到5次)，似乎我找到了另一个可能导致这个错误的原因。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|406472|在我的例子中，我在头文件中输入了错误的内容：|406473|#include+"MyClass.h""|code-block|syntax|javascript|406474|只有在检查完整个输出后，我才发现编译器在这一行发出了警告。|406475|现在，我删除了额外的引号，我的QObject编译得很好！|406476|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I know that this is a very old question, but it seems to be still interesting (I've been here at least 4 or 5 times in the last months) and seems like I found another reason for which is possible to get this error.

In my case in the header file I wrongly typed:

<pre><code>#include "MyClass.h""
</code></pre>

Only after inspecting the whole output I found out that at that line the compiler was emitting a warning.

Now that I removed the additional quotation mark my QObject compiles perfectly!

blocks|key|188361|text|对我来说，原因是:一些头文件或源文件没有包含在QT的项目文件中|type|unstyled|depth|inlineStyleRanges|entityRanges|data|188362|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

For me, this is the cause: some header or source file not included in QT's project file

blocks|key|188413|text|在我的例子中，我将问题QObject祖先的.h和.cpp文件放在项目的子文件夹中。当我将它们移到CMakeLists.txt+(项目根文件夹)旁边时，它成功链接了。我可能遗漏了一些在子目录中包含mocs文件的CMake命令。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|188414|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

In my case I had the .h and the .cpp file for the problematic QObject ancestor in subfolders of the project. When I moved them next to the CMakeLists.txt (project root folder) it linked successfully. I'm probably missing some CMake command to include mocs fot files in subdirectories.

I inherited a class from QObject : 

<pre><code>class Parent: public QObject
{
 Q_OBJECT
 QObject* cl;

public:
 Parent(QObject *parent=0):QObject(parent) {
 cl = NULL;
 }

 QObject* getCl() const {
 return cl;
 }
 void setCl(QObject *obj) {
 cl = obj;
 }
};
</code></pre>

But when I write :

<pre><code>Parent ev;
</code></pre>

I get the following error:

<pre><code>main.obj:-1: error: LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall Parent::metaObject(void)const " (?metaObject@Parent@@UBEPBUQMetaObject@@XZ)

main.obj:-1: error: LNK2001: unresolved external symbol "public: virtual void * __thiscall Parent::qt_metacast(char const *)" (?qt_metacast@Parent@@UAEPAXPBD@Z)

main.obj:-1: error: LNK2001: unresolved external symbol "public: virtual int __thiscall Parent::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@Parent@@UAEHW4Call@QMetaObject@@HPAPAX@Z)
</code></pre>

Unresolved external symbol "public: virtual struct QMetaObject const * __thiscall Parent

Visual Studio

编译器

我从QObject继承了一个类：class Parent: public QObject{    Q_OBJECT    QObject* cl;public:    Parent(QObject *parent=0):QObject(parent) {        cl = NULL;    }    QObject* getCl() const {        return cl;    

问未解析的外部符号"public:虚拟结构QMetaObject const * __thiscall Parent
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