On Tue, May 9, 2023 at 4:38 AM Larry Garfield <la...@garfieldtech.com> wrote:
>
> Ilija Tovilo and I would like to offer another RFC for your consideration.
> It's been a while in coming, and we've evolved the design quite a bit just in
> the last week so if you saw an earlier draft of it in the past few months, I
> would encourage you to read it over again to make sure we're all on the same
> page. I'm actually pretty happy with where it ended up, even if it's not the
> original design. This approach eliminates several hard-to-implement edge
> cases while still providing a lot of functionality in one package.
>
> https://wiki.php.net/rfc/property-hooks
>
> --
> Larry Garfield
> la...@garfieldtech.com
>
> --
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>
Hi Larry.
Suppose that I just want to cache once and freeze, and I don't want to
create additional hidden property. Please make a judgement on the
validity of this syntax:
```
public string $prop1 {
get => $field ??= $this->heavyTask($this->propx, $prop->y);
set => null;
}
```
Explanation:
* Since the ```get``` hook uses ```$field```, the engine will create a
backing store value with name ```$prop1```, and will be filled at the
first call only. The later call will use the already stored value.
* Since no new value is assigned to ```$field``` in the ```set```
hook, the value stored in ```$prop1``` is still the same as before.
* Since any return statement will be discharged in ```set``` hook, the
assignment chaining is safe to use and the value which is transferred
is alway the rightmost value (not the value returned by the ```set```
hook).
```
$varx = $obj->prop1 = "hello"; // $varx value is "hello", and
$obj->prop1 value is unchanged
```
But, this statement below is NOT ALWAYS correct for "cache once and freeze":
```
public string $prop1 {
set => $field ??= $this->heavyTask($this->propx, $prop->y);
}
```
Explanation:
* Since default ```get``` hook can be called before ```set``` hook,
backing store value with name ```$prop1``` will still be empty.
* Otherwise, I have to duplicate the body of the ```set``` hook into
```get``` hook to prevent an emptiness backing store.
Please give a comment.
Thanks.
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