单身模板 [英] singleton template
问题描述
我在代码中发现这个我正在维护
模板< class SingletonClass>
SingletonClass * Singleton< SingletonClass> :: instance（）
{
静态SingletonClass _instance;
return& _instance;
}
有迹象表明构造函数在某些情况下被调用超过
（跟踪在
模板的一个实例中。
使用静态数据是否存在潜在问题？
- -
Nick Keighley
Nick Keighley写道：
我在代码中发现这个我维护
模板< class SingletonClass>
SingletonClass * Singleton< SingletonClass> :: instance（）
{
静态SingletonCla ss _instance;
return& _instance;
}
有迹象表明构造函数被调用超过
一次
在某些情况下（跟踪
模板的一个实例）。
使用静态数据是否存在潜在问题？
有时候，这个
代码没有任何内在错误（但你可能会考虑使用引用）。请参阅
_Modern C ++ Design_的第6章，比你想知道的更多
关于C ++中的单身人士。
干杯！ --M
嗨Nick，
有迹象表明构造函数被调用更多
在某些情况下比一次更多（在模板的一个
实例中进行追踪）。
是否存在潜在问题使用静态数据？
使用Visual C ++ 6.0时我遇到了这个问题。但是在发布模式下只有
，而不是在调试模式下。可能是优化器的问题是什么？$！$
解决方案是移动实例的实现（）
.h从.h到.cpp文件的方法。
希望它有所帮助...
Tilman
mlimber写道：
Nick Keighley写道：
我在代码中发现这个我维护
模板< class SingletonClass>
SingletonClass * Singleton< SingletonClass> :: instance（）
{
静态SingletonClass _instance;
return& _instance;
}
有迹象表明构造函数在某些情况下被调用超过
一次
（在
模板的一个实例中进行追踪）。
有没有潜力使用静态数据的问题？
有时候，这个
代码没有任何内在错误（但你可能会考虑使用引用）。请参阅
_Modern C ++ Design_的第6章，比你想知道的更多
关于C ++中的单身人士
..
谢谢，我继续留意MCD的意思，但我不是
舒适的模板。
比如这样的事情： -
class PerformanceDataItemIniFile：public PanelIniFile，
public Singleton< PerformanceDataItemIniFile>
...
让我担心它继承自使用自身作为参数的东西。
-
Nick Keighley
Hi,
I found this in code I was maintaining
template <class SingletonClass>
SingletonClass* Singleton<SingletonClass>::instance ()
{
static SingletonClass _instance;
return &_instance;
}
there are indications that the constructor is getting called more than
once
in some circumstances (tracing in one of the instantiations of the
template).
Are there potential problems with the use of static data?
--
Nick Keighley
Nick Keighley wrote:Hi,
I found this in code I was maintaining
template <class SingletonClass>
SingletonClass* Singleton<SingletonClass>::instance ()
{
static SingletonClass _instance;
return &_instance;
}
there are indications that the constructor is getting called more than
once
in some circumstances (tracing in one of the instantiations of the
template).
Are there potential problems with the use of static data?There are sometimes, but there''s nothing inherently wrong with this
code (you might consider using references instead, however). See
chapter 6 of _Modern C++ Design_ for more than you ever wanted to know
about singletons in C++.
Cheers! --M
Hi Nick,
there are indications that the constructor is getting called more
than once in some circumstances (tracing in one of the
instantiations of the template).
Are there potential problems with the use of static data?I had exactly this problem when using Visual C++ 6.0. But only
in Release mode, not in Debug mode. Perhaps a problem with
the optimizer...?!
The solution was to move the implementation of the instance()
method from the .h to the .cpp file.
Hope it helps...
Tilman
mlimber wrote:Nick Keighley wrote:Hi,
I found this in code I was maintaining
template <class SingletonClass>
SingletonClass* Singleton<SingletonClass>::instance ()
{
static SingletonClass _instance;
return &_instance;
}
there are indications that the constructor is getting called more than
once
in some circumstances (tracing in one of the instantiations of the
template).
Are there potential problems with the use of static data?
There are sometimes, but there''s nothing inherently wrong with this
code (you might consider using references instead, however). See
chapter 6 of _Modern C++ Design_ for more than you ever wanted to know
about singletons in C++..
thanks, I keep on meaning to getting around to MCD, but I am not
comfortable with templates.
For instance something like this:-
class PerformanceDataItemIniFile : public PanelIniFile,
public Singleton< PerformanceDataItemIniFile >
...
worries me it inherits from something that uses itself as a parameter.
--
Nick Keighley
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