Pattern matching via switch?

Steven Schveighoffer schveiguy at gmail.com
Tue Mar 17 14:33:53 UTC 2020


On 3/17/20 8:04 AM, rikki cattermole wrote:
> On 18/03/2020 12:59 AM, Steven Schveighoffer wrote:
>> I think he's looking for object pattern matching. i.e. you give it an 
>> Object, and it runs a block of code based on the derived type.
> 
> In case this syntax is unknown:
> 
> if (MyObject1 myObject = cast(MyObject1)obj) {
>      ...
> } else if (MyObject2 myObject = cast(MyObject2)obj) {
>      ...
> } else {
>      ...
> }

Yes, look a few posts up, that was my recommendation.

I don't think there's a "pleasant" way to do this in D. You can do it 
with delegates, but that's a bit uglier than a switch statement, and has 
been rejected by the OP. However, I don't think the syntax requested is 
going to be added to D, as it's an odd syntax:

case SomeType inst: // inst now defined as SomeType

So that's probably the best bet.

-Steve


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