Mysql query result access by field name

[Steven Schveighoffer]

On 5/21/18 10:59 AM, kdevel wrote:
> On Monday, 21 May 2018 at 14:17:23 UTC, Steven Schveighoffer wrote:
>>>     Data f;
>>>     allrows[0].toStruct (f);
>>>
>>> I haven't checked this.
>>
>> This only works if your struct has exactly the same layout as the fields.
>>
>> So if, for instance, your rows are selected "title", "name", 
>> "surname", but your data type orders them name, surname, title, you 
>> won't be happy with the result.
> 
> Haven't seen this. Then there is no more field-safety than in the OP's 
> "assembler" code.
> 
> In the other post you wrote
> 
> | 1. Use ResultRange instead of the Row interface. This provides
> | a couple of ways to use column names, .asAA to get all the data
> | in a nice AA format (they are still variants),
> 
> The AA format can than be used to fill the struct automatically 
> (detecting missing and excess fields) like in this code:
> 
>     T toStructX(T) (string[string] a)
>     {
>        T t;
>        bool[string] bookkeep;
>        foreach (i, m; t.tupleof) {
>           string key = T.tupleof[i].stringof;
>           if (key !in a) {
>              stderr.writefln ("missing key <%s>", key);
>              continue;
>           }
>           t.tupleof[i] = a[key].to!(typeof (m));
>           bookkeep[key] = true;
>        }
>        foreach (x, y; a)
>           if (x !in bookkeep)
>              stderr.writefln ("excess key-value pair <%s>:<%s>", x, y);
>        return t;
>     }

Yes, this is very similar to what I do in my serialization library, 
except I don't use the AA, I keep a map of indexes based on the index of 
the field in the tuple to avoid allocation associated with an AA.

Note that your incoming AA is going to be a Variant[string].

-Steve