I've done this a couple of times before but I always had issues, e.g. functions and property calls would be mixed in. But I think I have a good go-to function now:

import std.algorithm;
import std.conv;
import std.string;
import std.stdio;
import std.range;

struct Foo
{
    int one = 1;
    @property int test() { return 1; }
    int three = 3;
    string[string] aa;
    string toString() { return prettyFieldsString(this); }
}

string prettyFieldsString(T)(T t)
    if (is(T == struct) || is(T == class))
{
    Appender!string result;
    Appender!(string[]) fields;
    Appender!(string[]) values;

    foreach (member; __traits(allMembers, T))
    {
        mixin("
        static if (!is( FunctionTypeOf!(t." ~ member ~ ") ))
        {
            static if (member != " ~ `"toString"` ~ ")
            {
                fields.put(member);
                values.put(to!string(__traits(getMember, t, " ~ `"` ~
member ~ `"` ~ ")));
            }
        }
        ");
    }

    size_t spaceLen = 1;
    foreach (field; fields.data)  // should use reduce!() here..
        spaceLen = max(spaceLen, field.length);

    alias std.array.replicate replicate;
    string spaceString = replicate(" ", spaceLen);

    foreach (field, value; lockstep(fields.data, values.data))
        result.put(format("%s: %s%s\n", field, replicate(" ", spaceLen
- field.length), value));

    return result.data;
}

void main()
{
    Foo foo;
    foo.aa["foo"] = "bar";
    writeln(foo);
}

Sample output: http://paste.pocoo.org/show/558492/

I've had to put everything into one foreach loop since there are still some CTFE bugs I run into. I also had to add a check against toString, otherwise I get an infinite loop in the toString() call.

Anyway, feel free to use/improve this function.

On 2012-02-29 10:58, Andrej Mitrovic wrote:
> I've done this a couple of times before but I always had issues, e.g.
> functions and property calls would be mixed in. But I think I have a
> good go-to function now:
>
> import std.algorithm;
> import std.conv;
> import std.string;
> import std.stdio;
> import std.range;
>
> struct Foo
> {
>      int one = 1;
>      @property int test() { return 1; }
>      int three = 3;
>      string[string] aa;
>      string toString() { return prettyFieldsString(this); }
> }
>
> string prettyFieldsString(T)(T t)
>      if (is(T == struct) || is(T == class))
> {
>      Appender!string result;
>      Appender!(string[]) fields;
>      Appender!(string[]) values;
>
>      foreach (member; __traits(allMembers, T))
>      {
>          mixin("
>          static if (!is( FunctionTypeOf!(t." ~ member ~ ") ))
>          {
>              static if (member != " ~ `"toString"` ~ ")
>              {
>                  fields.put(member);
>                  values.put(to!string(__traits(getMember, t, " ~ `"` ~
> member ~ `"` ~ ")));
>              }
>          }
>          ");
>      }
>
>      size_t spaceLen = 1;
>      foreach (field; fields.data)  // should use reduce!() here..
>          spaceLen = max(spaceLen, field.length);
>
>      alias std.array.replicate replicate;
>      string spaceString = replicate(" ", spaceLen);
>
>      foreach (field, value; lockstep(fields.data, values.data))
>          result.put(format("%s: %s%s\n", field, replicate(" ", spaceLen
> - field.length), value));
>
>      return result.data;
> }
>
> void main()
> {
>      Foo foo;
>      foo.aa["foo"] = "bar";
>      writeln(foo);
> }
>
> Sample output: http://paste.pocoo.org/show/558492/
>
> I've had to put everything into one foreach loop since there are still
> some CTFE bugs I run into. I also had to add a check against toString,
> otherwise I get an infinite loop in the toString() call.
>
> Anyway, feel free to use/improve this function.

Seems like what I have in my serialization library Orange:

https://github.com/jacob-carlborg/orange/blob/master/orange/util/Reflection.d

"fieldsOf" and "getValueOfField". These work only on instance variables and don't care if the variable is public or not.

-- 
/Jacob Carlborg

On 2/29/12, Jacob Carlborg <doob@me.com> wrote:
> Seems like what I have in my serialization library Orange:

Sweet. I was gonna take a look at Orange for just this purpose. Thanks.