定义自定义输出工具 [英] defining a custom output facility
问题描述
我想创建一个自定义输出工具。换句话说，我希望
一个对象，其使用类似于std :: cout / std :: cerr，但提供更多
的灵活性。而不是简单地将参数写入stdout / stderr，
我希望它写入stdout，写入文件和/或调用日志
函数。
所以我的输出函数可能如下所示：
OutputFacility& OutputFacility :: put（const std :: string& s）{
cout<< S; //打印到stdout
write_to_logfile（s）; //也调用记录功能
返回* this;
}
现在我可以定义<<运算符是put（）的别名。
我的问题是：我是否必须为每种类型的输入定义put（）我希望
打印？即，我希望这适用于所有原始类型，
int，char，double，float等。
现在我''我认为OutputFacility类可以有一个
std :: ostringstream作为私有成员;每个版本的
OutputFacility :: put（）只会依次调用ostringstream put（）
方法，然后调用实际的输出函数（例如write_to_logfile（））。
似乎应该有一个更简单的方法来定义我的put
方法，即不是重载它并多次定义它，
如果我可以用魔法定义它一次参数意味着
取任何可以转换为字符串的东西。
感谢您的任何建议！
Matt
-
Matt Garman
发送电子邮件至： http://raw-sewage.net/index.php?file=email
I''d like to create a "custom output facility". In other words, I want
an object whose use is similar to std::cout/std::cerr, but offers more
flexibility. Instead of simply writing the parameter to stdout/stderr,
I''d like it to write to stdout, to a file, and/or call a logging
function.
So my output function might look something like this:
OutputFacility& OutputFacility::put(const std::string& s) {
cout << s; // print to stdout
write_to_logfile(s); // also calling logging function
return *this;
}
Now I can define the << operator to be an alias for put().
My question is: do I have to define put() for every type of input I
expect to print? I.e., I''d like this to work with all primitive types,
int, char, double, float, etc.
Right now I''m thinking that the OutputFacility class could have a
std::ostringstream as a private member; every version of
OutputFacility::put() would just in turn call the ostringstream put()
method, THEN call the actual output functions (e.g. write_to_logfile()).
It seems like there should be a simpler method of defining my put
method, i.e. instead of overloading it and defining it multiple times,
if I could just define it once with a "magical" parameter that means
"take anything that can be converted to a string".
Thanks for any advice!
Matt
--
Matt Garman
email at: http://raw-sewage.net/index.php?file=email
推荐答案
2004年1月13日星期二20:11:51 GMT，Matt Garman< fa ** @ not-real.bogus>写道：
On Tue, 13 Jan 2004 20:11:51 GMT, Matt Garman <fa**@not-real.bogus> wrote:
OutputFacility& OutputFacility :: put（const std :: string& s）{
cout<< S; //打印到stdout
write_to_logfile（s）; //也调用日志记录功能
return * this;
}
我的问题是：我是否必须为每种类型的输入定义put（）我希望打印？即，我希望这适用于所有原始类型，
int，char，double，float等。
OutputFacility& OutputFacility::put(const std::string& s) {
cout << s; // print to stdout
write_to_logfile(s); // also calling logging function
return *this;
}
My question is: do I have to define put() for every type of input I
expect to print? I.e., I''d like this to work with all primitive types,
int, char, double, float, etc.
看起来我可以豁免以下内容：
模板< class T> OutputFacility&安培; OutputFacility :: put（const T& x）{
std :: ostringstring os;
os<< x;
cout<< os.str（）;
write_to_logfile（os.str（））;
返回* this;
}
这似乎让我接近我想做什么。它适用于
字符串，c样式字符串（字符数组）和整数。但它并没有
识别std :: endl并且它会截断浮点数的一小部分。
有什么想法吗？
再次感谢！
Matt
-
Matt Garman
电子邮件地址： http://raw-sewage.net/index.php ？file = email
Matt Garman写道：
Matt Garman wrote:
我想创建一个自定义输出工具。换句话说，我想要一个使用类似于std :: cout / std :: cerr的对象，但提供更多的灵活性。而不是简单地将参数写入stdout / stderr，
我希望它写入stdout，文件和/或调用日志
函数。
所以我的输出函数可能看起来像这样：
OutputFacility& OutputFacility :: put（const std :: string& s）{
cout<< S; //打印到stdout
write_to_logfile（s）; //也调用日志功能
return * this;
}
现在我可以定义<< operator是put（）的别名。
我的问题是：我是否必须为我希望打印的每种输入定义put（）？即，我希望这适用于所有原始类型，
int，char，double，float等。
现在我正在考虑OutputFacility类可能有
std :: ostringstream作为私人成员;每个版本的OutputFacility :: put（）都会依次调用ostringstream put（）
方法，然后调用实际的输出函数（例如write_to_logfile（））。
似乎应该有一个更简单的方法来定义我的put
方法，即不是重载它并多次定义它，如果我可以用魔法定义它一次。参数意味着取出任何可以转换成字符串的东西。
感谢您的任何建议！
Matt
I''d like to create a "custom output facility". In other words, I want
an object whose use is similar to std::cout/std::cerr, but offers more
flexibility. Instead of simply writing the parameter to stdout/stderr,
I''d like it to write to stdout, to a file, and/or call a logging
function.
So my output function might look something like this:
OutputFacility& OutputFacility::put(const std::string& s) {
cout << s; // print to stdout
write_to_logfile(s); // also calling logging function
return *this;
}
Now I can define the << operator to be an alias for put().
My question is: do I have to define put() for every type of input I
expect to print? I.e., I''d like this to work with all primitive types,
int, char, double, float, etc.
Right now I''m thinking that the OutputFacility class could have a
std::ostringstream as a private member; every version of
OutputFacility::put() would just in turn call the ostringstream put()
method, THEN call the actual output functions (e.g. write_to_logfile()).
It seems like there should be a simpler method of defining my put
method, i.e. instead of overloading it and defining it multiple times,
if I could just define it once with a "magical" parameter that means
"take anything that can be converted to a string".
Thanks for any advice!
Matt
模板< typename T>
OutputFacility&
operator<< （OutputFacility& out，T const& out）
{
return out.put（lexical_cast< std :: string>（s））;
}
http： //www.boost.org/libs/conversion...m#lexical_cast
template< typename T >
OutputFacility&
operator << ( OutputFacility& out, T const& out )
{
return out.put( lexical_cast< std::string >( s ) );
}
http://www.boost.org/libs/conversion...m#lexical_cast
Matt Garman写道：
Matt Garman wrote:
这似乎让我接近我想做什么。它适用于
字符串，c样式字符串（字符数组）和整数。但它并没有识别std :: endl并且它会截断浮动的小数部分。
This seems to get me "close" to what I want to do. It works for
strings, c-style strings (char arrays), and integers. But it doesn''t
recognize std::endl and it truncates the fraction part of a float.
而是写一个换行符的函数，然后刷新ostream。
因为你的OutputFacility类不是一个ostream，它不行。
我没看到浮动截断，它对我有用。发布一个可编辑的
例子。
-
Andrew
std::endl is specific to ostreams. It is not declared as a newline, but
rather a function that writes a newline, then flushes the ostream.
Since your OutputFacility class isn''t an ostream, it won''t work.
I don''t see the float truncation, it works for me. Post a compilable
example.
--
Andrew
这篇关于定义自定义输出工具的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
