RAII is an awesome design and very useful to accomplish tasks like “I want something automatically done and cleaned up nicely at the end of current scope”.
I use following class to temporally change the global state of logger and intercept all logs, for the log verifications in testing.
class LoggingTracer{
std::unique_ptr<LoggingTracerImpl> impl;
public:
// temporary set log level, and trace if not changelevelonly
explicit LoggingTracer(const int level, bool changelevelonly);
LoggingTracer(const LoggingTracer&) = delete;
LoggingTracer(LoggingTracer&&) = delete;
~LoggingTracer();
std::vector<std::string> log_content();
};
I try to replace the global object with a new one and switch it back when finished. The Logging tracer will hold the old object:
LoggingTracer::LoggingTracer(const int level, const bool changelevelonly)
: impl(new LoggingTracerImpl()) {
impl->changelevelonly = changelevelonly;
// store current
thallium::get_global_manager().swap(impl->mnger_holder);
}
LoggingTracer::~LoggingTracer() {
// revert to before
thallium::get_global_manager().swap(impl->mnger_holder);
}
Then I use LoggingTracer in a function:
TEST(Coordinator, Register) {
ti_test::LoggingTracer{1, true};
// do the test
}
But nothing that I intended happens after the construction of LoggingTracer…The first line doesn’t work. Why? because I just forget to name that object, then it just immediately destruct!
The correct way:
TEST(Coordinator, Register) {
ti_test::LoggingTracer DONTFORGETME{1, true};
// do the test
}
Another silly mistake!