Hello Phil,

Thank you for posting in our community!

I have been looking into your question and as mentioned in our State Persistence Limitations section here:

getStateAsString method uses JSON.stringify() method to convert the original objects to a JSON string. JSON.stringify() does not support Functions, thats why the IgrGridState component will ignore the columns formatter, filters, summaries, sortStrategy, cellClasses, cellStyles, headerTemplate and bodyTemplate properties.

Having this in mind, what I can say is that this behavior is expected and in order to restore the cellClasses, you should assign them again when restoring the grid state.

For example:

component.css
.cellBackground {
    background-color: green;
}

component.tsx

<IgrGrid autoGenerate="false" ref={gridRef} data={DATA}>
    <IgrGridState ref={gridStateRef}></IgrGridState>
    <IgrColumn
        field="ID"
        header="Product ID"
        cellClasses={cellClassesHandler}
    ></IgrColumn>
    ...
</IgrGrid>

const cellClassesHandler = {
    cellBackground: (rowData: any, columnKey: string, cellValue: any, rowIndex: number) => cellValue < 4,
};

The above configuration will set the background color to green for the cells with values 1, 2 ,3. 

Then, when restoring the state, the cellClasses input property should be set to the custom cellClassesHandler object literal since the state ignores the column cell classes.

function restoreGridState() {
    const state = window.localStorage.getItem(stateKey);

    if (state) {
        gridStateRef.current.applyStateFromString(state, []);
        gridRef.current.getColumnByName("ID").cellClasses = cellClassesHandler;
    }
}

The result of the above configuration could be observed in the below attachment:

Additionally, regarding the issue discussed in the following forum thread here, what I can say is that this behavior has been identified and fixed and will be available in the next official release.

Attached could be found a small sample demonstrating my suggestion regarding the cellClasses.

Please test it on your side and let me know if you need any further assistance regarding this matter.

Looking forward to your reply.

Sincerely,
Riva Ivanova
Software Developer

5482.IgrGrid - state persistence cellClasses.zip