Could replaced types be pointer types?

[preslavrachev]

I was playing around with type replacements for some of our JSON column, and was curios to figure out, whether the code below would work:

[[types]]
  [types. Match]
  # match configuration ...

  [types. Replace]
    type = "*models.SomeModel"

turns out, it does not. From my experiments, it looks like type replacements need a concrete value type, even for nillable fields. I am aware that this is a convention that the the Go team has adopted for types whose zero value could be NULL, but, as Russ Cox says, a pointer could do the job equally well, and it has the advantage that one is not leaking SQL-specific types to the rest of the code.

So, my question is if it is possible to support pointer types, or if it works already, what is the specific syntax to achieve it?

[stephenafamo]

Technically, it shouldn't matter to SQLBoiler what types you replace with as long as it satisfies the sql.Scanner and driver.Valuer interfaces.

Whether it actually works or not depends on the database driver you use. For example, does the driver allow you to do this?

// Imagine users has id, custom_col
row, _ := db.QueryRow("select * from users limit 1")

var id int
var customCol *CustomColStruct
rows.Scan(&id, &customCol)

That becomes a double pointer which some drivers may complain about.

[preslavrachev]

To the first point, the generator actually fails with:

Error: unable to generate output: failed to format template

  77    }
  78 
  79 
  80 // Generated where
  81 
>>>> type whereHelper*models_SomeModel struct { field string }

To the second, while I understand the logic, I still think that this could be solved using a little generation during the generation phase. It is easy to determine if a variable's type is value or pointer. Thus, the code above can become:

var id int
var customCol *CustomColStruct
rows.Scan(&id, customCol)

[preslavrachev]

On a second thought, rows.Scan(&id, customCol) will not work because customCol is nil. I get your point with the double referencing now.