Hello,

With structs, I understand that "invariant checking" is called (from dlang tour):

It's called after the constructor has run and before the destructor is called.
It's called before entering a member function
invariant() is called after exiting a member function.

But, is is possible to have the invariant checking be performed
whenever a field is directly set?

For example, suppose a struct "S", has a field "x". I would like to
have invariance check in cases such as:

S.x = 4;

Maybe there is a hidden set field function that gets called that
might be exploitable??

Thoughts on this? Possible? Better paths that I should consider?

Best Regards,
James

On Sunday, 8 August 2021 at 11:30:41 UTC, james.p.leblanc wrote:

It's called after the constructor has run and before the destructor is called.
It's called before entering a member function
invariant() is called after exiting a member function.

You can make a field set function like so:

struct S
{
  private int x_;
  int x(int value) { return this.x_ = value; }
  int x() { return this.x_; }
}

This will then run invariants.

(boilerplate can automate that for you. https://code.dlang.org/packages/boilerplate cough self-advertisement cough)

On Sunday, 8 August 2021 at 11:36:51 UTC, FeepingCreature wrote:

struct S
{
  private int x_;
  int x(int value) { return this.x_ = value; }
  int x() { return this.x_; }
}

FC,

Thanks! This is exactly what I had hoped might be possible!

I had made some naive "newbie-D" attempts at something like this
be couldn't get anything to work. Thanks for providing an exable
of the exact code that would work. Much obliged!

Best Regards,
James

PS Even more important than solving my immediate problem, I have
gained a better understanding of the struct and its member functions.