在“测试模式”中打印信息但不在“正常执行” [英] Print information in "test mode" but not in "normal execution"
问题描述
我使用c ++中的应用程序使用特殊的dprintf函数打印信息,这是一个示例:
I am using an application in c++ that uses a special dprintf function to print information, this is an example:
dprintf(verbose, "The value is: %d", i);
做什么是当我定义verbose为测试目的,然后打印信息,在正常执行我不定义它,我没有看到无用的信息在屏幕上。我的问题是我如何做这个功能或实现相同的想法。
What is doing is when I define verbose for test purposes then I print the information and when I am working in normal execution I do not define it and I do not see useless information in the screen. My question is how can I do that function or implement the same idea?.
推荐答案
我尽量避免使用var-arg - 两种主要原因:
I try to avoid using var-arg c-style functions for two main reasons:
- 它们不是类型安全的,不能使用运算符<<
- 当提供的参数太少或太多时,他们无法识别
使用 boost :: fusion
,它以类型安全的方式提供参数。它迭代这些参数,当遇到%
时打印出来。如果给定的参数太少或太多,则抛出异常。
I've made a way that works using boost::fusion
, which is given arguments in a type-safe way. It iterates over those arguments, printing out them when a %
is encountered. If too few or too many arguments were given, an exception is thrown.
仍有一个问题:Variadic宏在C ++中尚未标准化。所以,我做了两个版本。一个工作与当前的C ++。您必须使用
There is one problem still: Variadic macros are not yet standard in C++. So, i have made two versions. One that work with current C++. You have to invoke it using
dprintf("name: %, value: %\n", ("foo", 42));
然后。使用可变宏的另一个版本可以通过定义一个预处理符号来使用,该符号可以让你写
Then. The other version, using variadic macros, can be used by defining a preprocessor symbol, which enables you to write
dprintf("name: %, value: %\n", "foo", 42);
这是代码。 boost.fusion
提供了更多详细信息:
Here is the code. The boost.fusion
provides more details for this:
#include <boost/fusion/include/sequence.hpp>
#include <boost/fusion/include/make_vector.hpp>
#include <boost/fusion/include/next.hpp>
#include <stdexcept>
#include <iostream>
template<typename IterS, typename IterSeqE>
void print_vec(IterS b, IterS e, IterSeqE, IterSeqE) {
while(b != e) {
if(*b == '%') {
if(++b != e && *b == '%') {
std::cout << '%';
} else {
throw std::invalid_argument("too many '%'");
}
} else {
std::cout << *b;
}
++b;
}
}
template<typename IterS, typename IterSeqB, typename IterSeqE>
void print_vec(IterS b, IterS e, IterSeqB seqb, IterSeqE seqe) {
while(b != e) {
if(*b == '%') {
if(++b != e && *b == '%') {
std::cout << '%';
} else {
std::cout << *seqb;
return print_vec(b, e, next(seqb), seqe);
}
} else {
std::cout << *b;
}
++b;
}
throw std::invalid_argument("too few '%'");
}
template<typename Seq>
void print_vec(std::string const& msg, Seq const& seq) {
print_vec(msg.begin(), msg.end(), begin(seq), end(seq));
}
#ifdef USE_VARIADIC_MACRO
# ifdef DEBUG
# define dprintf(format, ...) \
print_vec(format, boost::fusion::make_vector(__VA_ARGS__))
# else
# define dprintf(format, ...)
# endif
#else
# ifdef DEBUG
# define dprintf(format, args) \
print_vec(format, boost::fusion::make_vector args)
# else
# define dprintf(format, args)
# endif
#endif
// test, using the compatible version.
int main() {
dprintf("hello %, i'm % years old\n", ("litb", 22));
}
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