I come from languages that don't offer structs, I have this json load function that has to keep some data and intuitively I've written a struct, I've read about the differences, heap vs stack, value vs reference, but know I think i am overthinking it.

Is this decent:
	bool loadFromFile (string path)
	{
		auto data = readText(path);
	        JSONValue parsed = parseJSON(data);
		
		struct AtlasSpriteData
		{
			SDL_Rect clipRectangle;
			int xOffset;
			int yOffset;
		}
		AtlasSpriteData[string] dict;

	        foreach( string name, value; parsed["frames"] ){
			SDL_Rect clipRectangle;
                        auto spriteSourceSize = value["spriteSourceSize"];
			clipRectangle.x = to!int(frame["x"].toString());
			clipRectangle.y = to!int(frame["y"].toString());
			clipRectangle.w = to!int(frame["w"].toString());
			clipRectangle.h = to!int(frame["h"].toString());
			int xOffset = to!int(spriteSourceSize["x"].toString());
			int yOffset = to!int(spriteSourceSize["y"].toString());
			auto data = AtlasSpriteData(clipRectangle, xOffset, yOffset);
			dict[name] = data;
		}

Or should I use a class for that AtlasSpriteData?
reading about it I get the impression everytime I'll look up data from that dictionary data will get copied ?

On 24/08/2014 11:56 p.m., nikki wrote:
> I come from languages that don't offer structs, I have this json load
> function that has to keep some data and intuitively I've written a
> struct, I've read about the differences, heap vs stack, value vs
> reference, but know I think i am overthinking it.

Here's a simple way of working it out.
If you're using arrays of a type, use classes.
If you're storing lots of data inside it, classes.
If you need inheritance, classes.
If you have simple data for returning/argument passing then struct.

Basically, small, short lived allocations stack. Long lived, large allocations, classes.

At least that's my opinion.

On Sunday, 24 August 2014 at 11:56:44 UTC, nikki wrote:
> I come from languages that don't offer structs, I have this json load function that has to keep some data and intuitively I've written a struct, I've read about the differences, heap vs stack, value vs reference, but know I think i am overthinking it.
>
> Is this decent:
> 	bool loadFromFile (string path)
> 	{
> 		auto data = readText(path);
> 	        JSONValue parsed = parseJSON(data);
> 		
> 		struct AtlasSpriteData
> 		{
> 			SDL_Rect clipRectangle;
> 			int xOffset;
> 			int yOffset;
> 		}
> 		AtlasSpriteData[string] dict;
>
> 	        foreach( string name, value; parsed["frames"] ){
> 			SDL_Rect clipRectangle;
>                         auto spriteSourceSize = value["spriteSourceSize"];
> 			clipRectangle.x = to!int(frame["x"].toString());
> 			clipRectangle.y = to!int(frame["y"].toString());
> 			clipRectangle.w = to!int(frame["w"].toString());
> 			clipRectangle.h = to!int(frame["h"].toString());
> 			int xOffset = to!int(spriteSourceSize["x"].toString());
> 			int yOffset = to!int(spriteSourceSize["y"].toString());
> 			auto data = AtlasSpriteData(clipRectangle, xOffset, yOffset);
> 			dict[name] = data;
> 		}
>
> Or should I use a class for that AtlasSpriteData?
> reading about it I get the impression everytime I'll look up data from that dictionary data will get copied ?

Your struct instance will occupy only 24 bytes. It's ok even if you will copy it. I would avoid heap allocation in this case. Also what is 'frame' variable? I don't see local declaration of it. Or you just forgot to replace 'value' with 'frame'. Does not JSONValue.integer fit in this case instead of to!int(JSONValue.toString()) ?

Reading does not perform copy if you access struct directly as dict[name].some_field. Copying is performed only if you pass struct by value or assign it to variable.

On Sun, 24 Aug 2014 11:56:42 +0000
nikki via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com> wrote:

> Or should I use a class for that AtlasSpriteData?
> reading about it I get the impression everytime I'll look up data
> from that dictionary data will get copied ?

this will copy:

  auto sd = dict[0];

this will copy:

  foreach (sd; dict) { ... }

this will not:

  const *sd = &dict[0];

this will not:
  foreach (ref sd; dict) { ... }


hope you got the idea.

On Sun, 24 Aug 2014 11:56:42 +0000
nikki via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com> wrote:

> Or should I use a class for that AtlasSpriteData?
> reading about it I get the impression everytime I'll look up data
> from that dictionary data will get copied ?
p.s.

this will not copy:

  auto sd = "mysprite00" in dict;

'sd' is of type 'AtlasSpriteData*' here.

On Sunday, 24 August 2014 at 11:56:44 UTC, nikki wrote:
> I come from languages that don't offer structs, I have this json load function that has to keep some data and intuitively I've written a struct, I've read about the differences, heap vs stack, value vs reference, but know I think i am overthinking it.
>
> Is this decent:
> 	bool loadFromFile (string path)
> 	{
> 		auto data = readText(path);
> 	        JSONValue parsed = parseJSON(data);
> 		
> 		struct AtlasSpriteData
> 		{
> 			SDL_Rect clipRectangle;
> 			int xOffset;
> 			int yOffset;
> 		}
> 		AtlasSpriteData[string] dict;
>
> 	        foreach( string name, value; parsed["frames"] ){
> 			SDL_Rect clipRectangle;
>                         auto spriteSourceSize = value["spriteSourceSize"];
> 			clipRectangle.x = to!int(frame["x"].toString());
> 			clipRectangle.y = to!int(frame["y"].toString());
> 			clipRectangle.w = to!int(frame["w"].toString());
> 			clipRectangle.h = to!int(frame["h"].toString());
> 			int xOffset = to!int(spriteSourceSize["x"].toString());
> 			int yOffset = to!int(spriteSourceSize["y"].toString());
> 			auto data = AtlasSpriteData(clipRectangle, xOffset, yOffset);
> 			dict[name] = data;
> 		}
>
> Or should I use a class for that AtlasSpriteData?
> reading about it I get the impression everytime I'll look up data from that dictionary data will get copied ?

In this case class makes sense (assuming AtlasSpriteData has few instances that will be shared around a lot). But you could also use a pointer to a struct, especially if you manually allocate it and want to avoid the GC. Also, you can read data from the associative array by reference (basic example, no error checking):

ref AtlasSpriteData spriteData(string name) { return dict[name]; }