A.B

If A is null, crash.

A?.B : writeln("HAHA");

No crash, ignored, equivalent to

if (A is null) writeln("HAHA"); else A.B;

On Sunday, 2 June 2019 at 07:55:27 UTC, Amex wrote:
> A.B
>
> If A is null, crash.
>
> A?.B : writeln("HAHA");
>
> No crash, ignored, equivalent to
>
> if (A is null) writeln("HAHA"); else A.B;

The "optional" package on dub [1] has a .dispatch method that does this:

    auto d = some(A());

    // Dispatch to one of its methods

    d.dispatch.f(); // calls a.f, returns some(4)
    d.dispatch.inner.g(); // calls a.inner.g, returns some(7)

    // Use on a pointer or reference type as well
    A* e = null;

    // If there's no value in the reference type, dispatching
    // works, and produces an optional
    assert(e.dispatch.f() == none);
    assert(e.dispatch.inner.g() == none);


Full example: https://run.dlang.io/is/SmsGQu

[1] https://code.dlang.org/packages/optional

On Sunday, 2 June 2019 at 14:37:48 UTC, Paul Backus wrote:
> On Sunday, 2 June 2019 at 07:55:27 UTC, Amex wrote:
>> A.B
>>
>> If A is null, crash.
>>
>> A?.B : writeln("HAHA");
>>
>> No crash, ignored, equivalent to
>>
>> if (A is null) writeln("HAHA"); else A.B;
>
> The "optional" package on dub [1] has a .dispatch method that does this:
>
>     auto d = some(A());
>
>     // Dispatch to one of its methods
>
>     d.dispatch.f(); // calls a.f, returns some(4)
>     d.dispatch.inner.g(); // calls a.inner.g, returns some(7)
>
>     // Use on a pointer or reference type as well
>     A* e = null;
>
>     // If there's no value in the reference type, dispatching
>     // works, and produces an optional
>     assert(e.dispatch.f() == none);
>     assert(e.dispatch.inner.g() == none);
>
>
> Full example: https://run.dlang.io/is/SmsGQu
>
> [1] https://code.dlang.org/packages/optional

thanks.

On Sunday, 2 June 2019 at 07:55:27 UTC, Amex wrote:
> A.B
>
> If A is null, crash.
>
> A?.B : writeln("HAHA");
>
> No crash, ignored, equivalent to
>
> if (A is null) writeln("HAHA"); else A.B;

safeAccess from iz does this : https://github.com/Basile-z/iz/blob/master/import/iz/sugar.d#L1666