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August 08, 2021 Proper way to protect (lock) a struct field after initialization ?? | ||||
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 | Hello All. Is there a standard way to protect a field of a struct after Is this possible with a struct? If not, I suppose a class (object) would be needed? If so, Thanks in advance, James | |||
August 08, 2021 Re: Proper way to protect (lock) a struct field after initialization ?? | ||||
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 Posted in reply to james.p.leblanc | On Sunday, 8 August 2021 at 10:11:37 UTC, james.p.leblanc wrote: >Hello All. Is there a standard way to protect a field of a struct after Is this possible with a struct? If not, I suppose a class (object) would be needed? If so, Thanks in advance, James
Perhaps you tried it, realized you could still access it within the same module, and concluded that it didn't work? Consider note #2 at that link: "Symbols with private visibility can only be accessed from within the same module." Import the struct into another module and test the visibility there and you'll get the behavior you're looking for. | |||
August 08, 2021 Re: Proper way to protect (lock) a struct field after initialization ?? | ||||
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Posted in reply to jfondren | On Sunday, 8 August 2021 at 10:19:46 UTC, jfondren wrote: >On Sunday, 8 August 2021 at 10:11:37 UTC, james.p.leblanc wrote: >Hello All. Is there a standard way to protect a field of a struct after Is this possible with a struct? If not, I suppose a class (object) would be needed? If so, Thanks in advance, James
Perhaps you tried it, realized you could still access it within the same module, and concluded that it didn't work? Consider note #2 at that link: "Symbols with private visibility can only be accessed from within the same module." Import the struct into another module and test the visibility there and you'll get the behavior you're looking for. Hej JFondren, Wow, thanks for the quick response. I had read that about the modules ... Based on you kind reply, I went back over my example and found that I With a quick fix-up edit, it indeed is working as your explanation. Now, I proceed onto the trickier part of my endeavor ... Thanks again, and Best Regards, (Sorry for the noise...) | |||
August 08, 2021 Re: Proper way to protect (lock) a struct field after initialization ?? | ||||
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 Posted in reply to james.p.leblanc | On 8/8/21 3:11 AM, james.p.leblanc wrote:
> Hello All.
>
> Is there a standard way to protect a field of a struct after
> the struct has been initialized?
>
> Is this possible with a struct?
>
> If not, I suppose a class (object) would be needed? If so,
> are there any simple pointers to an example of this?
>
> Thanks in advance,
>
> James
>
I understand your question differently from jfondren. You may be looking for a 'const' (or 'immutable') member:
struct S {
const int i;
this(int i) {
// This will work because "first assignment is initialization"
this.i = i;
}
}
void main() {
auto s = S(42);
// This won't work
s.i = 43;
// This won't work either
s = S(44);
}
Ali
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August 08, 2021 Re: Proper way to protect (lock) a struct field after initialization ?? | ||||
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Posted in reply to Ali Çehreli | On Sunday, 8 August 2021 at 10:40:51 UTC, Ali Çehreli wrote:
>
> I understand your question differently from jfondren. You may be looking for a 'const' (or 'immutable') member:
>
> struct S {
> const int i;
>
> this(int i) {
> // This will work because "first assignment is initialization"
> this.i = i;
> }
> }
>
> void main() {
> auto s = S(42);
>
> // This won't work
> s.i = 43;
>
> // This won't work either
> s = S(44);
> }
>
> Ali
Hello Again Ali,
Excellent! I had tried (an erroneous) variant of this idea earlier ... but
also failed with my attempt.
I am appreciating very much the example you have provided. I will try
this approach as well for the problem I am working on. (Some details on
my path forward remain unclear ...)
Best Regards,
James
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