[Question] How to get all referenced instances for a particular instance?

[youshengCode]

There is a way to get a list of all referenced instances which have used the current entity?

Take an IfcCartesianPoint for example, there is a way to get all entities that have used this point?

Assemblies and versions affected:

Using the latest stable build, Xbim.Essentials 5.1.323

Steps (or code) to reproduce the issue:

For this piece of IFC, placements #11, #14 have used point #7.

Just start with #7, could I retrieve a list with #11, #14 and others, if there are more entities that have referenced this point?

#7=IFCCARTESIANPOINT((0.,0.,0.));
#8=IFCDIRECTION((1.,0.,0.));
#9=IFCDIRECTION((0.,1.,0.));
#10=IFCDIRECTION((0.,0.,1.));
#11=IFCAXIS2PLACEMENT3D(#7,#10,#8);
#12=IFCAXIS2PLACEMENT2D(#13,$);
#13=IFCCARTESIANPOINT((0.,0.));
#14=IFCAXIS2PLACEMENT3D(#7,#10,#8);

Minimal file to reproduce the issue:

This piece of IFC comes from the buildingSMART sample test files.

[Sample-Test-Files/cube-advanced-brep.ifc at master · buildingSMART/Sample-Test-Files (github.com)](https://github.com/buildingSMART/Sample-Test-Files/blob/master/IFC 4.0/BuildingSMARTSpec/cube-advanced-brep.ifc)

Expected behavior:

Get a list of instance or entity labels, who referenced or have used this instance.

Additional Details

I found a similar method Traverse() in the IfcOpenShell, basically I'm trying to accomplish the same thing.

IfcOpenShell/file.py at fc05bdf6d6465251fec8e279493d1bf5f3017617 · IfcOpenShell/IfcOpenShell (github.com)

[martin1cerny]

Yes, this is possible. Have a look at the code we use to delete an entity. That also needs to inspect the model and find all relating entities to keep the model consistent.

[youshengCode]

Thanks for your quick response and your advice, Martin,

That's exactly what I'm looking for.

But seems it doesn't take care all referring types.

I have used the same method for GetReferingTypes, and ReplaceReferences in ModelHelper.cs. In the ReplaceReferences, I just commented out those lines for replacing the value.

using (var model = IfcStore.Open(fileName))
{
    var entities = model.Instances.OfType<IIfcCartesianPoint>();
    var uniqueTypes = new HashSet<Type>(entities.Select(e => e.GetType()));
    var referingTypes = new HashSet<ReferingType>(uniqueTypes.SelectMany(t => GetReferingTypes(model, t)));
    foreach (var referingType in referingTypes)
        ReplaceReferences<IPersistEntity, IPersistEntity>(model, entities, referingType, null);
}

For example, I can't find #123 has been used in #122. (this piece is from the same sample file in the description).

#122=IFCBSPLINESURFACEWITHKNOTS(3,1,((#123,#124),(#125,#126),(#127,#128),(#129,#130)),.UNSPECIFIED.,.F.,.F.,.U.,(4,4),(2,2),(0.,1224.74487139159),(3.,4.),.UNSPECIFIED.);
#123=IFCCARTESIANPOINT((-0.5,0.5,0.));
#124=IFCCARTESIANPOINT((-0.5,-0.5,0.));
#125=IFCCARTESIANPOINT((-0.561004233964073,0.27232909936926,0.333333333333333));
#126=IFCCARTESIANPOINT((-0.27232909936926,-0.561004233964073,0.333333333333333));
#127=IFCCARTESIANPOINT((-0.622008467928146,0.0446581987385206,0.666666666666667));
#128=IFCCARTESIANPOINT((-0.0446581987385206,-0.622008467928146,0.666666666666667));
#129=IFCCARTESIANPOINT((-0.683012701892219,-0.183012701892219,1.));
#130=IFCCARTESIANPOINT((0.183012701892219,-0.683012701892219,1.));

It seems like the referring types of IFCCARTESIANPOINT not taking IFCBSPLINESURFACEWITHKNOTS.

Did I miss something? Please let me know. Thanks a lot.

[martin1cerny]

IFCBSPLINESURFACEWITHKNOTS is one two classes in IFC using nested (2D) lists. The code looking for references might be missing these. Feel free to contribute to the project with a pull request fixing this issue. All contributions are most welcome.

[youshengCode]

I fixed this issue in the ModelHelper, it works like a charm. Thanks a lot, Martin.

I added a new prop in the struct ReferingType.

private struct ReferingType
{
    public ExpressType Type;
    public List<ExpressMetaProperty> SingleReferences;
    public List<ExpressMetaProperty> ListReferences;
    public List<ExpressMetaProperty> NestedListReferences;
}

And added the related part to get referring types.

private static IEnumerable<ReferingType> GetReferingTypes(IModel model, Type entityType)
{
    // ......
    
    foreach (var type in types)
    {
        if (!ReferingTypesCache.TryGetValue(type.Type, out ReferingType rt))
        {
            var singleReferences = type.Properties.Values.Where(p =>
                p.EntityAttribute != null && p.EntityAttribute.Order > 0 &&
                p.PropertyInfo.PropertyType.GetTypeInfo().IsAssignableFrom(entityType)).ToList();
            var listReferences = type.Properties.Values.Where(p =>
                p.EntityAttribute != null && p.EntityAttribute.Order > 0 &&
                p.PropertyInfo.PropertyType.GetTypeInfo().IsGenericType &&
                p.PropertyInfo.PropertyType.GenericTypeArgumentIsAssignableFrom(entityType)).ToList();
             //add nested list references
            var nestedListReferences = type.Properties.Values.Where(p =>
                p.EntityAttribute != null && p.EntityAttribute.Order > 0 &&
                p.PropertyInfo.PropertyType.GetTypeInfo().IsGenericType &&
                p.PropertyInfo.PropertyType.GetItemTypeFromGenericType().IsGenericType &&
                p.PropertyInfo.PropertyType.GetItemTypeFromGenericType().GenericTypeArgumentIsAssignableFrom(entityType)).ToList();
            if (!singleReferences.Any() && !listReferences.Any() && !nestedListReferences.Any())
                continue;

            rt = new ReferingType { Type = type, SingleReferences = singleReferences, ListReferences = listReferences, NestedListReferences = nestedListReferences };
            ReferingTypesCache.TryAdd(type.Type, rt);
        }
        referingTypes.Add(rt);
    }
    return referingTypes;
}

Then I used the ReplaceReferences (the one with the IEnumerable argument) to check and replace the entities.

private static void ReplaceReferences<TEntity, TReplacement>(IModel model, IEnumerable<TEntity> entities, ReferingType referingType, TReplacement replacement)
    where TEntity : IPersistEntity where TReplacement : TEntity
{
    // ......
        
    foreach (var toCheck in entitiesToCheck)
    {
        // ......

        //check for nested list references
        foreach (var pInfo in referingType.NestedListReferences.Select(p => p.PropertyInfo))
        {
            var pVal = pInfo.GetValue(toCheck);
            if (pVal == null) continue;

            //it might be uninitialized optional item set
            if (pVal is IOptionalItemSet optSet && !optSet.Initialized)
                continue;

            //or it is non-optional item set implementing IList
            if (!(pVal is IList nestedItemSet))
                throw new XbimException($"Unable to remove items from {referingType.Type.Name}.{pInfo.Name}. No IList implementation.");

            for (int i = 0; i < nestedItemSet.Count; i++)
            {
                if (!(nestedItemSet[i] is IList itemSet))
                    throw new XbimException($"Unable to remove items from {referingType.Type.Name}.{pInfo.Name}. No IList implementation.");

                for (int j = 0; j < itemSet.Count; j++)
                {
                    var item = itemSet[j];
                    if (!hash.Contains(item))
                        continue;
                    itemSet.RemoveAt(j);
                    if (replacement != null)
                        itemSet.Insert(j, replacement);
                    else
                        j--; // keep in sync
                }
            }
        }
    }

}

I have checked the documentation, there are IfcBSplineSurface and IfcBSplineSurfaceWithKnots using the nested list in the property ControlPointsList. I have tested this piece of code with those two classes. It works fine for me for now.

I will make a pull request later, but please notice that

I have only updated the GetReferingTypes(IModel model, Type entityType) and ReplaceReferences<TEntity, TReplacement>(IModel model, IEnumerable entities, ReferingType referingType, TReplacement replacement) these two methods mentioned above.

Since I am not very familiar with the whole project, this needs to be further adapted in other related methods.