Looping Through Structs

[mar_cuz]

Hi Guys,

Just mucking around in a test project to familiarise myself with the new additions to game makers code and I was wondering if it is possible to loop through stucts and if so how?

Thanks,

 

[Nidoking]

Are you attempting to loop through the values contained in a single struct, or to loop through a collection of structs?

 

[FrostyCat]

The basic book line for looping through a struct (GMS 2.3.1):

var keys = variable_struct_get_names(strc);
for (var i = array_length(keys)-1; i >= 0; --i) {
    var k = keys[i];
    var v = strc[$ k];
    /* Use k and v here */
}

For GMS 2.3.0, substitute strc[$ k] with variable_struct_get(strc, k).

 

[Nidoking]

I suppose it works as an academic exercise, but I can't imagine what practical purpose there would be to this. If you've got data that you want to loop through, pretty much any other structure makes more sense. If you've got a struct, the data should represent specific things that you'd want to access by variable names to do the things they're meant to do.

 

[FrostyCat]

I suppose it works as an academic exercise, but I can't imagine what practical purpose there would be to this.

General merging, deep cloning/copying, and nested value-wise equivalence all rely on the struct iteration book line I described.

Given the testimonials I've received for these posts and libraries being useful, it doesn't make much sense calling it just an academic exercise.

 

[Nidoking]

Okay, I can see the value in those operations. I'd still want to write my own specific functions for handling those, because it seems like there's always going to be some minor thing you'd want to do differently in any real-world situation where you'd have to write some wrapper for the general function, and it helps me control exactly what my structs are doing, but I get the point.

 

[Daniel Mallett]

I found your post because this is what I needed to do. It works fine but the variables are not being listed in any kind of order I can see. Will I have to re-order them manually? I was expecting either the creation order or alphabetical order.

Sorry to necro bump this thread but it is directly relevant. To the OP.

 

[Alice]

@Daniel Mallett Yes, the struct keys are sorted in a seemingly random order; might have something to do with underlying hash codes (basically, string keys are converted to an integer using some very specific calculations for more efficient implementation).

As far as I can tell, you can't retrieve the creation order (you'd need to pretty much store it in a separate array), but you can easily convert these keys to alphabetical order:

var some_struct = { lorem: 123, ipsum: 456, dolor: 789, sit: 1011, amet: 1213 };
var keys = variable_struct_get_names(some_struct);
show_debug_message(keys); // will show the messy unordered keys
array_sort(keys, true /* ascending order */);
show_debug_message(keys); // now the keys are neatly ordered!

 

[kburkhart84]

All said, structs aren't meant for actual ordered data....arrays are however. You should use the right tool for the job for sure. If you make your own topic about specifically what you are doing we might be able to suggest what could be the best(or better, in our opinion) way to go about it @Daniel Mallett

 

[Daniel Mallett]

Thanks.