Readonly field for class type

[Seb]

On Thursday, 15 March 2018 at 10:57:52 UTC, Mike Parker wrote:
> On Thursday, 15 March 2018 at 10:55:16 UTC, Mike Parker wrote:
>
>>
>> class A {
>>     private int _value = 12;
>>
>>     int value() @property { return _value; }
>>     void updateValue() { value = 13; }
>> }
>>
>> ...
>> auto a = new A();
>> writeln(a.value);
>> a.updateValue();
>> writeln(a.value);
>
> Sorry. I overlooked that B.a is const.

It still works, the `value` just needs to be `const` (or `inout`) 
and _value needs to be used in updateValue:

class A {
     private int _value = 12;

     int value() const { return _value; }
     void updateValue() { _value = 13; }
}


auto a = new A();
writeln(a.value);
a.updateValue();
writeln(a.value);


In action: https://run.dlang.io/is/Tk1rY1

@Robert: If you need this a lot, the accessors package might be 
interesting to you:

https://code.dlang.org/packages/accessors