www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - How I can iterate data in structure

reply "Suliman" <evermind live.ru> writes:
void main()
{
	
	auto result = readconfig();

	foreach (_; result)
	{
		// I want to iterate result that I got from structure.
	}
}

auto readconfig()
{
	struct ConfigStruct
	{
		string key1;
		string key2;
	}

	ConfigStruct confstruct = ConfigStruct();
	confstruct.key1="Ivan";
	confstruct.key2="admin";

	return confstruct;

}
Aug 22 2014
parent reply "bearophile" <bearophileHUGS lycos.com> writes:
Suliman:


 void main()
 {
 	
 	auto result = readconfig();

 	foreach (_; result)
 	{
 		// I want to iterate result that I got from structure.
 	}
 }

 auto readconfig()
 {
 	struct ConfigStruct
 	{
 		string key1;
 		string key2;
 	}

 	ConfigStruct confstruct = ConfigStruct();
 	confstruct.key1="Ivan";
 	confstruct.key2="admin";

 	return confstruct;

 }


Be careful to make ConfigStruct a static struct.

auto readconfig() {
     static struct ConfigStruct {
         string key1, key2;
     }

     return ConfigStruct("Ivan", "admin");
}

void main() {
     import std.stdio;
     auto result = readconfig();

     foreach (field; result.tupleof) {
         writeln(field);
     }
}

Bye,
bearophile
Aug 22 2014
parent reply "Suliman" <evermind live.ru> writes:
foreach (field; result.tupleof)


Why I should here specify type of iterable element, but not first 
element that I use for iteration?

I mean:
foreach (_some_type_possible_enum_ field; result)

?
Aug 22 2014
next sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Suliman:


foreach (field; result.tupleof)


 Why I should here specify type of iterable element, but not 
 first element that I use for iteration?

 I mean:
 foreach (_some_type_possible_enum_ field; result)

 ?


I don't understand your question. In my code I have not specified 
types in the foreach.

Bye,
bearophile
Aug 22 2014
prev sibling parent reply "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:
On Friday, 22 August 2014 at 08:44:51 UTC, Suliman wrote:

foreach (field; result.tupleof)


 Why I should here specify type of iterable element, but not 
 first element that I use for iteration?

 I mean:
 foreach (_some_type_possible_enum_ field; result)

 ?


You mustn't, because your struct could have fields of different 
types. When you `foreach()` over a tuple, the compiler unrolls 
the loop body, which allows it to use a (potentially) different 
type on each iteration.

If you don't want this, and all the fields have the same type, 
you can iterate over an array made from the fields:

     foreach (field; [result.tupleof]) {
         writeln(field);
     }
Aug 22 2014
parent "Gary Willoughby" <dev nomad.so> writes:
On Friday, 22 August 2014 at 10:44:31 UTC, Marc Schütz wrote:

 On Friday, 22 August 2014 at 08:44:51 UTC, Suliman wrote:

foreach (field; result.tupleof)


 Why I should here specify type of iterable element, but not 
 first element that I use for iteration?

 I mean:
 foreach (_some_type_possible_enum_ field; result)

 ?


 You mustn't, because your struct could have fields of different 
 types. When you `foreach()` over a tuple, the compiler unrolls 
 the loop body, which allows it to use a (potentially) different 
 type on each iteration.

 If you don't want this, and all the fields have the same type, 
 you can iterate over an array made from the fields:

     foreach (field; [result.tupleof]) {
         writeln(field);
     }


Or you could implement opApply or range primitives in the struct.

http://ddili.org/ders/d.en/foreach_opapply.html
http://dlang.org/phobos/std_range.html
Aug 22 2014