• Andrew Chapman (30/30) May 12 2016 Hi guys, apologies for the silly question, but I come from the
• Adam D. Ruppe (17/21) May 12 2016 Yes.
• Andrew Chapman (3/12) May 12 2016 That's wonderful Adam, thank you! I actually had your book

Andrew Chapman <nycran gmail.com> writes:

Hi guys, apologies for the silly question, but I come from the 
world of dynamic languages and I'm wondering if it's possible to 
set struct values basic on dynamic variables?

e.g.

struct Person {
    string firstName;
    string lastName;
}

void main() {
    string[string] map;

    map["firstName"] = "Homer";
    map["lastName"] = "Simpson";
}

Is it possible to iterate through the hash map and set the struct 
values using the key/value pairs?

Something like this:

e.g.
Person p1;

foreach(key,val; map) {
    p1[key] = val;
}

The problem I'm trying to solve is that I'm wanting to write a 
generic "model" class that can read a record from a database and 
populate a known struct from the database values.  I have seen 
the "allMembers" method from the traits module that can give me 
the names of the struct fields, but I am unsure if it's even 
possible to set the struct values using variable/dynamic names.

Any help will be greatly appreciated!
Cheers,
Andrew.

Adam D. Ruppe <destructionator gmail.com> writes:

On Thursday, 12 May 2016 at 20:52:46 UTC, Andrew Chapman wrote:
 I have seen the "allMembers" method from the traits module that 
 can give me the names of the struct fields, but I am unsure if 
 it's even possible to set the struct values using 
 variable/dynamic names.


Yes.

You can't loop over the hash and set values on the struct, since 
looping a hash is a run time operation, but you can loop over 
struct members.

So, the trick is to loop over the struct members (a compile-time 
operation) and set them (converting type with `std.conv.to` if 
necessary) if the value is in the hash.

foreach(member; __traits(allMembers, YourStruct))
   if(member in yourhash)
    __traits(getMember, your_object, member) = 
to!right_type(yourhash[member]);


basically, it is a bit more complex to filter out inappropriate 
fields and such, but that's the idea.

Check out the sample chapter of my book 
https://www.packtpub.com/application-development/d-cookbook to 
see more, you can get the reflection chapter free on that site.

Andrew Chapman <nycran gmail.com> writes:

On Thursday, 12 May 2016 at 21:01:06 UTC, Adam D. Ruppe wrote:

 foreach(member; __traits(allMembers, YourStruct))
   if(member in yourhash)
    __traits(getMember, your_object, member) = 
 to!right_type(yourhash[member]);


 basically, it is a bit more complex to filter out inappropriate 
 fields and such, but that's the idea.

 Check out the sample chapter of my book 
 https://www.packtpub.com/application-development/d-cookbook to 
 see more, you can get the reflection chapter free on that site.

That's wonderful Adam, thank you!  I actually had your book 
previously bookmarked - I should probably buy it :-)