In go v1.19.2, I'm hoping to be able to use generics to delete objects in a database using gorm. The roadblock I'm finding is that I can't seem to be able to create a new object based on a given generic type and then populate the Id value in order to pass that value to the orm's Delete() function.
Below is my sample code that fails to compile. I've implemented 4 different ways trying to update the Id of the newly created generic-passed type, but all variations give me compiler errors. Each compiler error is noted in the code.
package main
// based on: https://stackoverflow.com/a/33642734/5572674
type ModelA struct {
ModelC
FiledA string
}
type ModelB struct {
ModelC
FiledB string
}
type ModelC struct {
Id int `orm:"pk"`
}
type IModelC interface {
setId(id int)
}
func (m *ModelC) setIdViaPtr(id int) {
m.Id = id
}
func (m *ModelC) setId(id int) {
m.Id = id
}
// mock of orm.Delete
func Delete(md interface{}, cols ...string) (int64, error) {
return 0, nil
}
func DeleteGenericById[T ModelC](id int) error {
tPtr := new(T)
// 4 diferent attempts ... all fail with compiler errors
tPtr.setIdViaPtr(id) //COMPILE ERROR: tPtr.setIdViaPtr undefined (type *T is pointer to type parameter, not type parameter)
(*tPtr).setIdViaPtr(id) //COMPILE ERROR: (*tPtr).setIdViaPtr undefined (type T has no field or method setIdViaPtr)
(*tPtr).setId(id) // COMPILE ERROR: (*tPtr).setId undefined (type T has no field or method setId)
(*ModelC)(*tPtr).setId(id) // COMPILE ERROR: cannot convert *tPtr (variable of type T constrained by ModelC) to *ModelC (cannot convert ModelC (in T) to *ModelC
_, err := Delete(tPtr)
return err
}
I implemented code in 4 different ways in order to update the generic type Id but all resulted in compile errors noted in comments in the code.
