Getting errors with .getCellvalue - "Cannot read properties of null (reading '0')"

[Daniel_Rieger]

Hi guys,

I'm relatively new to scripting, so I've mostly used scripts I find in this amazing community and adapted them to my tables. Once such script I've tweaked to create junction tables. It automatically creates entries in a junction table when a linked record field is updated. It has been working pretty well for a 5-6 months now, then all of a sudden earlier today, it started giving the error:

ERROR
TypeError: Cannot read properties of null (reading '0')
at main on line 38"

Usually I can figure out what is going on and fix it, but this really has me stumped. I didn't touch the script today (I'm the only one who manages them). I took a snapshot of the base from this morning and the script works in that, so I tried to copy/paste the code from that to the live version, but it still didn't work. Which lead me to believe that has something to do with a change in the base, like a changed field or table name. 

So I thought, okay maybe someone accidentally changed a field name. Double checked everything like 26 times and all of the fields/table names look exactly the same. I was considering just migrating over to the snapshot from earlier today, but that is going to be a nightmare with sending out new links for forms and views to our afterschool instructors. Hoping someone can shed some insight on what is happening! Thanks in advance.

// @ts-nocheck
let projectsTable = base.getTable('Weekly Instructor Scheduling');
let projectQuery = await projectsTable.selectRecordsAsync({fields: ['Name', 'Subs (Pending)','Track Sub Pending']});
let projectRecords = projectQuery.records;

let companyTable = base.getTable('After School Instructors');
let companyQuery = await companyTable.selectRecordsAsync({fields: ['Name']});

let joinTable = base.getTable('Sub Accept/Reject Table');
let joinQuery = await joinTable.selectRecordsAsync({fields: joinTable.fields});

// Go through all the records in the class table
for (let projectRecord of projectRecords) {
    // For each class, get the linked instructor records
    let companyRecordsLinkedToProject = projectRecord.getCellValue('Subs (Pending)');
    if (!companyRecordsLinkedToProject) {
        continue;
    }

    // For each class, get the linked join records
    let joinRecordsLinkedToProject = projectRecord.getCellValue('Track Sub Pending');
    if (joinRecordsLinkedToProject === null) {
        // If there are no linked join records, use an empty array instead
        joinRecordsLinkedToProject = [];
    }

    // Create a Set of instructor record ids that are linked to the class.
    // A Set is like an array, but more efficient.
    let companyRecordIds = new Set();
    for (let linkedCompanyRecord of companyRecordsLinkedToProject) {
        companyRecordIds.add(linkedCompanyRecord.id);
    }

    // Loop over all join records linked to the class.
    for (let linkedJoinRecord of joinRecordsLinkedToProject) {
        // Get the full join record, not just name and id
        let joinRecord = joinQuery.getRecord(linkedJoinRecord.id);
// ERROR HERE
        let companyRecordLinkedToJoin = joinRecord.getCellValue('After School Instructors')[0];
// ERROR HERE
        let companyRecordId = companyRecordLinkedToJoin.id;

        // Remove this instructor record id from the Set.
        // @ts-ignore

        companyRecordIds.delete(companyRecordId);
    }

    // Now we have a Set of instructor record ids that don't have join records.
    for (let companyRecordIdToJoin of Array.from(companyRecordIds)) {
        // Create the join record linking this class and this instructor.
        let companyRecord = companyQuery.getRecord(companyRecordIdToJoin);
        let companyName = companyRecord.getCellValueAsString('Name');
        await joinTable.createRecordAsync({
            'Weekly Instructor Scheduling': [{id: projectRecord.id}],
            'After School Instructors': [{id: companyRecordIdToJoin}],
        });
    }
    

}

// Get Join Records Now that the Script has Run

let joinQueryTwo = await joinTable.selectRecordsAsync({fields: joinTable.fields});

let joinRecordsTwo = joinQueryTwo.records;

let nonMatches = joinRecordsTwo.filter(c => !c.getCellValueAsString('All Subs Pending').split(', ').includes(c.getCellValueAsString('After School Instructors')))

// Delete Irrelevant Records Now that the Script has Run

await joinTable.deleteRecordsAsync(nonMatches)

The error is on this line:

let companyRecordLinkedToJoin = joinRecord.getCellValue('After School Instructors')[0];

Final notes: This is a script in an automation that triggers on changes to the linked record field "Subs (Pending)" in the "Weekly Instructor Scheduling" table

[TheTimeSavingCo · Accepted solution]

Is there a record in your table where the field `After School Instructors` is empty?

[Daniel_Rieger]

Hey Adam,

Thanks for getting back to me!! Yes there are, but I've been very careful about which contact I use for the test trigger..... hold up. I think I know what you're saying. Just having one contact in the junction table missing would throw the error.... and you were right!!! Just fixed it, and it worked. Lol, an admin must have accidentally deleted the linked record in one of the junction table records, causing it to throw errors. 

I am so happy! I knew it must've been something small like that. Thank you Adam, you're a life saver!!

[TheTimeSavingCo]

Glad I could help!