Relationship Counts

One common type of subselect field is the count of related entites. For instance, you may want to load a Post or a list of Posts with the count of Comments on each Post. You can reuse your existing relationship definitions and add this count using the withCount method.

withCount

Adds a count of related entities as a subselect property. Relationships can be constrained at runtime by passing a struct where the key is the relationship name and the value is a function to constrain the query.

Name	Type	Required	Default	Description
relation	any	true		A single relation name or array of relation names to load counts.

By default, you will access the returned count using the relationship name appended with Count, i.e. comments will be available under commentsCount.

var post = getInstance( "Post" )
	.withCount( "comments" )
	.findOrFail( 1 );
	
post.getCommentsCount();

You can alias the count attribute using the AS syntax as follows:

var post = getInstance( "Post" )
	.withCount( "comments AS myCommentsCount" )
	.findOrFail( 1 );
	
post.getMyCommentsCount();

This is especially useful as you can dynamically constrain counts at runtime using the same struct syntax as eager loading with the with function.

var post = getInstance( "Post" )
	.withCount( [
	    "comments AS allCommentsCount",
	    { "comments AS pendingCommentsCount": function( q ) {
	        q.where( "approved", 0 );
	    } },
	    { "comments AS approvedCommentsCount": function( q ) {
	        q.where( "approved", 1 );
	    } }
	] )
	.findOrFail( 1 );

post.getAllCommentsCount();	
post.getPendingCommentsCount();
post.getApprovedCommentsCount();

Note that where possible it is cleaner and more readable to create a dedicated relationship instead of using dynamic constraints. In the above example, the Post entity could have pendingComments and approvedComments relationships. Dynamic constraints are more useful when applying user-provided data to the constraints like searching.