How to Add a Dynamic Child List to Parent in Apex Class || Trigger using map

Last Updated: 13-01-2024

Map<parentId, List<child>> 

Code without comments

Map<id, List<object>> parentIdAndChildRecordsMap = new Map<id, List<object>>();
for(object childRecord : Trigger) {
	if(parentIdAndChildRecordsMap.containsKey(childRecord.parentId__c)) {
		parentIdAndChildRecordsMap.get(childRecord.parentId__c).add(childRecord);
	} else {
		parentIdAndChildRecordsMap.put(
			childRecord.parentId__c, 
			new List<object>{childRecord}
		);
	}
}

Code with comments

// Define a map to store parent IDs and their associated child records
Map<id, List<object>> parentIdAndChildRecordsMap = new Map<id, List<object>>();

// Iterate through each object in the Trigger context (likely a trigger context variable)
for(object childRecord : Trigger) {
	// Check if the map already contains the parent ID
	if(parentIdAndChildRecordsMap.containsKey(childRecord.parentId__c)) {
		// Parent ID found, so add the child record to the existing list
		parentIdAndChildRecordsMap.get(childRecord.parentId__c).add(childRecord);
	} else {
		// Parent ID not found in the map
        		// Create a new entry in the map with the parent ID and a list containing the child record
		parentIdAndChildRecordsMap.put(
			childRecord.parentId__c, 
			new List<object>{childRecord}
		);
	}
}

Explanation

1. Map Definition: Map<Id, List<Object>> parentIdAndChildRecordsMap = new Map<Id, List<Object>>(); This line declares a map (parentIdAndChildRecordsMap) where keys are of type Id (presumably representing parent record IDs), and values are lists of type Object (presumably representing child records).
2. Loop Through Trigger Context: for (Object childRecord : Trigger) {: This loop iterates through each object in the Trigger context. The Trigger context typically holds records that caused the trigger to execute.
3. Check if Parent ID Exists in Map: if (parentIdAndChildRecordsMap.containsKey(childRecord.parentId__c)) {: Checks whether the map already contains the parent ID of the current childRecord.
4. Add Child Record to Existing List:  parentIdAndChildRecordsMap.get(childRecord.parentId__c).add(childRecord);: If the parent ID is already in the map, it retrieves the associated list of child records and adds the current childRecord to that list.
5. Create New Map Entry if Parent ID Not Found:  parentIdAndChildRecordsMap.put(childRecord.parentId__c, new List<Object>{childRecord});: If the parent ID is not found in the map, it creates a new entry in the map with the parent ID and a list containing the current childRecord.

In summary, this code efficiently organizes child records into lists based on their associated parent record IDs. This is useful for scenarios where you need to process related records together, such as when working with parent-child relationships in Salesforce or any other similar scenario in Apex development.