Post Edit delegate for an asset? (datatable)

Development Programming & Scripting C++
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1

I wish to track any modification to only a single datatable. A UDataTable has a delegate for that, but it is not accessible from an FDataTableRowHandle (const datatable).

afbeelding
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Currently I am using:

FCoreUObjectDelegates::OnObjectModified.AddUObject(this, &UMyObject::ActOnObjectChanged);

Where I have to check if any changed UObject happens to be this datatable. Another side effect which seems to be caused by this workaround is that I don’t get the most recent data from the DataTable during ActOnObjectChanged. It lags one edit behind, which breaks the system.

2

You can’t bind to the table member of FDataTableRowHandle because it’s a pointer to a const table, and the event is a member of that table.

DataTables should be treated as “const” at runtime, they are meant for static data only. If you want a Key/Value pair set at runtime then just use regular TMap’s.

Assuming this for an edit-time tool, if so, you can just cast the const away. FTableRowBase also has callbacks for when the table is modified, which you can override for a specific table struct.

You can also use the Data Validation system to validate tables on save and log errors etc.

3

It is used within an editor module to update an object on the editor panel when I update my datatable. The datatable itself is not modified through my code, I only want to know when it is modified during editor time. The FDataTableRowHandle format is used so I can use the datatable + row “picker” on the editor panel.

Is it not undefined behavior to const_cast away the const and then write to its delegate?

const_cast conversion - cppreference.com

4

The issue is that UObject::Modify is always called before changes are made, you want to find some kind of post-edit change delegate. They do exist but I can’t name them currently.

RE the const_cast - probably, but I’ve always found it works fine in practice. Design decisions at the engine level sometimes make it hard to care about const-correctness when making editor tools…

5

that post-edit delegate sounds like the way to go, I’d rather not mess with possible UB. I found something that might just be it, but I don’t know how to use it:

FDataTableEditorUtils::FDataTableEditorManager::Get().AddListener([]( ??? ) { });

It makes use of INotifyOnChanged (ListenerManager) of which I can’t find any example in engine .cpp files.

FDataTableEditorUtils::BroadcastPostChange(DataTable, EDataTableChangeInfo::RowList);

afbeelding
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6

bump

7

:up:

8

:arrow_up_small:

9

:up:

10

:wave:

11

Up :slight_smile:

12

let’s try again

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Make your class inherit from public FListenerManager<UDataTable, FDataTableEditorUtils::EDataTableChangeInfo>::BaseNotifyOnChanged, and override the PreChange and PostChange functions.

You can replace UDataTable in above with a more specific class you want.

class UMyDataTableListener : public UObject, public FListenerManager<UDataTable, FDataTableEditorUtils::EDataTableChangeInfo>::BaseNotifyOnChanged
{
    virtual void PreChange(const UDataTable* Changed, FDataTableEditorUtils::EDataTableChangeInfo ChangedType) override;
    virtual void PostChange(const UDataTable* Changed, FDataTableEditorUtils::EDataTableChangeInfo ChangedType) override;
}

Then do:

FDataTableEditorUtils::FDataTableEditorManager::Get().AddListener(this);

Don’t forget to remove the listener at some point.

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