Extending CsvBulkloader and ModelAdmin Class in Silverstripe 4 - php

Question

I am looking to extend Silverstripe's CSVBulkLoader class to do some business logic before/upon import.
In the WineAdmin Class (extending ModelAdmin), I have a custom loader defined with $model_importers property:
//WineAdmin.php
private static $model_importers = [
'Wine' => 'WineCsvBulkLoader'
];
In the WineCsvBulkLoader Class, the $columnMap property maps CSV columns to SS DataObject columns:
//WineCsvBulkLoader.php
use SilverStripe\Dev\CsvBulkLoader;
class WineCsvBulkLoader extends CsvBulkLoader
{
public $columnMap = [
// csv columns // SS DO columns
'Item Number' => 'ItemNumber',
'COUNTRY' => 'Country',
'Producer' => 'Producer',
'BrandName' => 'BrandName',
// etc
];
When the import is run, the WineCsvBulkLoader class is being invoked, but, the column mappings do not seem to work properly, returning values only where the [key] and [value] in the array are identical. Otherwise, the imported columns are empty. What could be causing this?
Additionally, the $duplicateChecks property is set to look for duplicates.
public $duplicateChecks = [
'ItemNumber' => 'ItemNumber'
];
}
What does the $duplicateChecks property actually do when there is a duplicate? Does it skip the record?
Can I use callbacks here?
In the docs, I found some code for an example method that splits data in a column into 2 parts and maps those parts to separate columns on the class:
public static function importFirstAndLastName(&$obj, $val, $record)
{
$parts = explode(' ', $val);
if(count($parts) != 2) return false;
$obj->FirstName = $parts[0];
$obj->LastName = $parts[1];
}
Is $obj the final import object? How does it get processed?
$val seems to be the value of the column in the csv being imported. Is that correct?
What is contained in $record?
Here are some additional enhancements I hope to make:
Read the Byte Order Marker, if present, upon import, and do something useful with it
Upon import, check for duplicate records, and if there are duplicates, I’d like to only update the columns in the record that have changed.
Delete records that are already in the database, that are not in the CSV being imported
Add whatever security measures are necessary to use this custom class securely.
Export CSV with BOM (byte order mark as UTF8)
I'm not looking for a complete answer, but appreciative of any insights.

Answer 1

I'll attempt to answer some of your questions based on SilverStripe 4.2.0:
Judging by the logic in CsvBulkLoader::findExistingObject the duplicateChecks property is used to help finding an existing record in order to update it (rather than create it). It will use defined values in the array in order to find the first record that matches a given value and return it.
What does the $duplicateChecks property actually do when there is a duplicate? Does it skip the record?
Nothing, it will just return the first record it finds.
Can I use callbacks here?
Kind of. You can use a method on the instance of CsvBulkLoader, but you can't pass it a callback directly (e.g. from _config.php etc). Example:
public $duplicateChecks = [
'YourFieldName' => [
'callback' => 'loadRecordByMyFieldName'
]
];
/**
* Take responsibility for loading a record based on "MyFieldName" property
* given the CSV value for "MyFieldName" and the original array record for the row
*
* #return DataObject|false
*/
public function loadRecordByMyFieldName($inputFieldName, array $record)
{
// ....
Note: duplicateChecks callbacks are not currently covered by unit tests. There's a todo in CsvBulkLoaderTest to add them.
Is $obj the final import object? How does it get processed?
You can see where these magic-ish methods get called in CsvBulkLoader::processRecord:
if ($mapped && strpos($this->columnMap[$fieldName], '->') === 0) {
$funcName = substr($this->columnMap[$fieldName], 2);
$this->$funcName($obj, $val, $record); // <-------- here: option 1
} elseif ($obj->hasMethod("import{$fieldName}")) {
$obj->{"import{$fieldName}"}($val, $record); // <----- here: option 2
} else {
$obj->update(array($fieldName => $val));
}
This is actually a little misleading, especially because the method's PHPDoc says "Note that columnMap isn't used." Nevertheless, the priority will be given to a value in the columnMap property being ->myMethodName. In both the documentation you linked to and the CustomLoader test implementation in the framework's unit tests, they both use this syntax to specifically target the handler for that column:
$loader->columnMap = array(
'FirstName' => '->importFirstName',
In this case, $obj is the DataObject that you're going to update (e.g. a Member).
If you don't do that, you can define importFirstName on the DataObject that's being imported, and the elseif in the code above will then call that function. In that case the $obj is not provided because you can use $this instead.
"Is it the final import object" - yes. It gets written after the loop that code is in:
// write record
if (!$preview) {
$obj->write();
}
Your custom functions would be required to set the data to the $obj (or $this if using importFieldName style) but not to write it.
$val seems to be the value of the column in the csv being imported. Is that correct?
Yes, after any formatting has been applied.
What is contained in $record?
It's the source row for the record in the CSV after formatting callbacks have been run on it, provided for context.
I hope this helps and that you can achieve what you want to achieve! This part of the framework probably hasn't had a lot of love in recent times, so please feel free to make a pull request to improve it in any way, even if it's only documentation updates! Good luck.