How to sort on a foreign key constraint's column count?

[daniel-res]

Your Question

Hello, I'm not sure on the best approach here, but am looking for some feedback. I want to be able to perform a sort based on the total count of the number of SubGroups associated with the same Group.

I have these two structs:

type SubGroup struct {
	gorm.Model
	
	Name           
	Status          int
}

type Group struct {
	gorm.Model
	
	Author       *string
	Color        string
	Name string
	
	SubGroups []*SubGroup
}

And am currently using the following approach to sorting on Group top-level columns. I have defined a method to dynamically pass in applicable column names, etc. to build up the required query.

var q = queries.Use(pageDb).Group
var builtQuery = q.WithContext(context.Background()).Preload(field.Associations)

var orderQuery = getFieldExpression(orderBy, sortBy)
if orderQuery != nil {
	builtQuery = builtQuery.Order(orderQuery)
}

func getSortedFieldExpression(orderBy, sortBy string) field.Expr {
	var columnField *field.Field = nil
	switch sortBy {
	case "author":
		var c = field.NewField(tableName, "author")
		columnField = &c
	case "color":
		var c = field.NewField(tableName, "color")
		columnField = &c
	case "totalStatuses":
		// ??? todo
	}
	
	if columnField == nil {
		return nil
	}
	
	if orderBy == "desc" {
		return columnField.Desc()
	}
	
	return columnField
}

Any help / suggestions is appreciate, thanks.