I'm having some trouble creating arrays that are themselves unique within multiple instances of an object. Example code:

class individual
{
    int a = 1; // placeholder for data
}

class individualList
{
    individual[] individuals;  // Something likely has to change here
}

void main()
{
    individualList list1 = new  individualList();
    assert(list1.individuals.length == 0);
    individual person1 = new individual();
    list1.individuals ~= person1;
    assert(list1.individuals.length == 1);

    individualList list2 = new individualList();
    assert(list2.individuals.length == 0); // breaks, list2.individuals.length is 1
}

I'd like the array "individuals" to be unique for each instance of individualList, but it seems to be using the same list among the different instances. The following code doesn't work as I don't know the required length of the arrays:

class individualList
{
    individual[] individuals = new individual[];  // Doesn't compile, requires length
}

I've looked a bit and don't see a solution to this within the documentation for arrays or objects.

Further information:
This is being used to parse a xml-style file, the example code is a base example, I'm having to do this list population a few times, one within another. Some lists have their count displayed before starting to add "individuals" so I could use a constructor, but some do not (to my knowledge) have that option, and I'd rather use one solution through the whole parser.

On Thursday, 14 March 2024 at 09:43:09 UTC, Jonathan wrote:

class individual
{
    int a = 1; // placeholder for data
}

class individualList
{
    individual[] individuals;  // Something likely has to change here
}

void main()
{
    individualList list1 = new  individualList();
    assert(list1.individuals.length == 0);
    individual person1 = new individual();
    list1.individuals ~= person1;
    assert(list1.individuals.length == 1);

    individualList list2 = new individualList();
    assert(list2.individuals.length == 0); // breaks, list2.individuals.length is 1
}

Shouldn't be. Each non static class member is a distinct thing in each instance of the class. They are not shared across instances. When I paste your code into run.dlang.io and add this:

    writeln(list1.individuals.length);
    writeln(list2.individuals.length);

No asserts trigger and I see this output as expected:

1
0

Is the code you pasted here exactly what you're running?

On Thursday, 14 March 2024 at 09:53:27 UTC, Mike Parker wrote:

class individual
{
    int a = 1; // placeholder for data
}

class individualList
{
    individual[] individuals;  // Something likely has to change here
}

void main()
{
    individualList list1 = new  individualList();
    assert(list1.individuals.length == 0);
    individual person1 = new individual();
    list1.individuals ~= person1;
    assert(list1.individuals.length == 1);

    individualList list2 = new individualList();
    assert(list2.individuals.length == 0); // breaks, list2.individuals.length is 1
}

    writeln(list1.individuals.length);
    writeln(list2.individuals.length);

1
0

You're right, my example code doesn't function as my nonworking code does, sorry about that.

No, this is not the same, the code that doesn't work is part of a 1000+ line parser, I thought this example would work the same. I'm trying multiple loops to get the same problem, but I'm having trouble getting it to do so. Will get back when I have a proper example.

The following seems the be the minimum required for this problem to pop up. I've changed the names to what I'm using in my code to make it more clear for me.

import std;
class SpectrumList
{
    int count = 2;
    Spectrum[] spectra;
}

class Spectrum
{
    PrecursorList precursorList = new PrecursorList();
}

class PrecursorList
{
 	int count = 3;
    Precursor[] precursors;
}

class Precursor
{
 	string a = "placeholder";
    string b = "loren ipsum";
}

void main()
{
   SpectrumList mySpectrumList = new SpectrumList;
   for(int j=0; j<mySpectrumList.count; ++j)
   {
   	    Spectrum mySpectrum = new Spectrum;
        writeln(mySpectrum.precursorList.precursors.length); // should always be 0
        assert(mySpectrum.precursorList.precursors.length == 0);
        for(int k=0; k<mySpectrum.precursorList.count; ++k)
        {
            Precursor myPrecursor = new Precursor;
            mySpectrum.precursorList.precursors ~= myPrecursor;
        }
        mySpectrumList.spectra ~= mySpectrum;
   }
}

Output from run.dlang.io:

0
3
core.exception.AssertError@onlineapp.d(32): Assertion failure
----------------
??:? [0x55676698b006]
??:? [0x55676698ac82]
??:? [0x5567669b11d6]
??:? [0x5567669927ef]
??:? [0x556766989d92]
onlineapp.d:32 [0x556766959f4c]
??:? [0x5567669924bc]
??:? [0x5567669923b6]
??:? [0x55676699220d]
/dlang/ldc-1.35.0/bin/../import/core/internal/entrypoint.d:42 [0x55676695a1d1]
??:? [0x7efc3bed5d8f]
??:? __libc_start_main [0x7efc3bed5e3f]
??:? [0x556766959c54]
Error: /tmp/onlineapp-ae55ed failed with status: 1

On Thursday, 14 March 2024 at 10:21:41 UTC, Jonathan wrote:

Classic. Instead of a static initializer rather uses a constructor for instances.

class Spectrum
{
    PrecursorList precursorList;
    this()
    {
        precursorList = new PrecursorList();
    }
}

On Thursday, 14 March 2024 at 10:21:41 UTC, Jonathan wrote:

You encounter a gotcha unfriendly construct of D. For every "new Spectrum", there is only one instant of mySpectrum.precursorList hence for subsequence iteration, the list is already filled with myPrecursor hence the assert problem. So either move that static new to constructor or in the loop

Cheers
Happy coding

On Thursday, 14 March 2024 at 12:00:37 UTC, Basile B. wrote:

class Spectrum
{
    PrecursorList precursorList;
    this()
    {
        precursorList = new PrecursorList();
    }
}

This seems to have solved the problem. This thought had crossed my mind at one point, then left before I could implement it. Really appreciate the help!