What is the _type column for polymorphism?
From the Rails Guide , in order to establish polymorphic relationships for one model, I need to add two columns for the corresponding table.
As shown in the figure below, the column is _id
used as a foreign key. But I can't figure out the use of the column _type
? What is its use?
The column is _type
used to determine which resource it comes from. In this case, the polymorphic resource can be one of Employee
or Product
. In other words: the image can refer to either the product or the employee.
The column _type
will contain the line "Employee" or "Product". When this link is available, Rails will use it to find out which model to use to load the linked object.