Getting nice print of struct for debugging

[Jacob Carlborg via Digitalmars-d-learn]

On 2017-02-20 17:04, Martin Tschierschke wrote:
> Hello,
> I have a little program where I am filling a struct with values from an
> regex match.
> Now I want to display the content of the struct for debugging purpose.
>
> If struct is named MyStruct
>
> I can print a list of the field names with:
>
> foreach(fieldname;FieldNameTuple!MyStruct){writef("%s ",fieldname);}
>
> If myvar is of type MyStruct how can I make a table like:
>
> fieldname_1: value_1
> fieldname_2: value_2
> .
> .
> fieldname_n: value_n
>
> Is there a way to do this with a single expression in D.
>
> Similar to a ruby call myvar.send(fieldname) to get the value from
> fieldname inside a loop?
> write(myvar); sure is working directly but I want to get the field names
> displayed, too.
>
> (A work around might be work with the format("%s",myvar) string and
> extract the values with an index?)

Yes, this works, I would say this is the simplest:

MyStruct s;

foreach (index, name ; FieldNameTuple!MyStruct)
     writefln("%s: %s", name, s.tupleof[index]);

If you want something more close to "send" in Ruby, you need to use a 
string mixin, like this:

foreach (name ; FieldNameTuple!MyStruct)
     writefln("%s: %s", name, mixin("s." ~ name));

The string mixin example works for methods, opDispatch and similar as 
well. The tupleof example, the first one, works only for fields.

-- 
/Jacob Carlborg