Casting JSONValues arrays to native arrays ... ??? ...

[Steven Schveighoffer]

On 9/24/21 12:58 AM, james.p.leblanc wrote:
> On Thursday, 23 September 2021 at 20:32:36 UTC, james.p.leblanc wrote:
>> On Thursday, 23 September 2021 at 19:18:11 UTC, james.p.leblanc wrote:
>>> On Thursday, 23 September 2021 at 19:04:47 UTC, Steven Schveighoffer 
>>> wrote:
>>>> On 9/23/21 2:20 PM, james.p.leblanc wrote:
>>
>> ```
>> Produces:
>>
>> typeid(jj): std.json.JSONValue, jj: 
>> {"ba":[true,false,true],"d":[1.23399999999999999]}
>> typeid(z5): question.main.MapResult!(__lambda2, 
>> JSONValue[]).MapResult, z5: [true, false, true]
>> z5: [true, false, true]
>>
> 
> Sigh ... my suggested "minor edit" above produces a "map result" instead of
> the desired native array ... here is the **fix** by appending ".array" 
> at the
> end (which is the suffix Steve originally offered).  The following gives
> the desired **bool[]** result.
> 
> ```d
> import std.array;
> 
>     auto z5 = jj["ba"].array.map!(v => v.get!bool).array;
>     writeln("typeid(z5): ", typeid(z5), ", z5: ", z5);
>     writeln("z5: ", z5);
> ```

At first I thought that was allocating 2 arrays, but I didn't realize 
`JSONValue.array` was an actual member! When I saw your original code, I 
assumed the `.array` call was a call to `std.array.array`, and that 
`JSONValue` was somehow usable as a range.

So yes, that's what I should have written.

I admit I have not used `JSONValue`. That `array` accessor is quite a 
poor name due to the vast prevalence of using `std.array.array` to make 
an array out of some range. When using vibe.d's JSON type, I usually do 
`jsval[]` to access the array portion.

Note, you may want to consider whether you actually need a concrete 
array, as using the map result is pretty much equivalent, yet doesn't 
allocate anything.

-STeve