Pre-condition and Post-condition in C++

Ok, let's check the method that realize DbC in standard C++. About realizing pre-condition, anybody think that an assert in a first part of function is effectual. That's right. And, it is also correct method about assert.

Then, do you realize post-condtion? You can not realize post-condition of DbC by an assert in a end part of function because post-condition is must executed after return code. And, you'll hope to write all conditions in a first part of function. This page that this site introduced yesterday answers that question well. You can use 'Destractor' to realize post-condition.

void foo()
{
struct Sentry
{ Sentry() { ...preconditions... }
~Sentry() { ...postconditions... }
} sentry;
...implementation...
}

Destractor is called when the instance goes out of scope. Therefore, You can check post-condition after the end of function by this method.