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Possible to overload assignment of struct field ??
Aug 24, 2021
james.p.leblanc
Aug 24, 2021
Ali Çehreli
Aug 24, 2021
james.p.leblanc
August 24, 2021
Gravatar of james.p.leblancPosted by james.p.leblancReply
james.p.leblanc
Gravatar of james.p.leblanc


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Greetings,

With a struct, there are many overload possibilities available.

However, I haven't been able to find how to overload assignment
of selected fields of a struct.

For example, suppose:

struct Foo{
  int a;
  int b;
  ...
}

void main(){
    auto x = Foo( 1, 2);  // so x now instantiates

    x.a = 100;             // suppose I wish to enforce that a<5??
...
}

(I understand this is basically a field "setter" idea that is most
often associated with classes. So, another way to state the quesion
might be: "How can a field setter be done on a already instantiated
struct?)

Best Regards,
James

August 23, 2021
Gravatar of Ali ÇehreliPosted by Ali Çehreli
in reply to james.p.leblanc		Reply
Ali Çehreli
Gravatar of Ali Çehreli
Posted in reply to james.p.leblanc


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On 8/23/21 10:25 PM, james.p.leblanc wrote:

So, you need a "property". Easy... :)

1) Rename the member e.g. as a_.

2) Write setter and getter functions named 'a'.

struct Foo{
  int a_;

  int a() const {
    return a_;
  }

  void a(int value) {
    a_ = value;
  }
}

void main(){
  auto x = Foo(1);
  x.a = 100;
  assert(x.a == 100);
}

Ali
August 24, 2021
Gravatar of james.p.leblancPosted by james.p.leblanc
in reply to Ali Çehreli		Reply
james.p.leblanc
Gravatar of james.p.leblanc
Posted in reply to Ali Çehreli


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On Tuesday, 24 August 2021 at 05:34:08 UTC, Ali Çehreli wrote:
> On 8/23/21 10:25 PM, james.p.leblanc wrote:
>
> So, you need a "property". Easy... :)
>
> 1) Rename the member e.g. as a_.
>
> 2) Write setter and getter functions named 'a'.
>
> struct Foo{
>   int a_;
>
>   int a() const {
>     return a_;
>   }
>
>   void a(int value) {
>     a_ = value;
>   }
> }
>
> void main(){
>   auto x = Foo(1);
>   x.a = 100;
>   assert(x.a == 100);
> }
>
> Ali

Ali,

Thank you ... yes!  This is exactly what I needed, I have done something
similar as you have shown for the "getter", but had a "brain-lock-up"
when thinking about the setter.

A bit embarassing for my, I admit.  But, on the positive side ... the
solution is now burned into my brain.

Thanks again and Kind Regards,
James