Create new row if table is empty.

[StewartLynch]

When my app launches, I want to be able to insert a new row into a table like Reminders if it is empty as you suggest as an exercise for the viewers in part 2 of the triggers section.
What would be the syntax for this or where should I look to find it?
I want to do this

try Property.insert{ Property.Draft(name: "New Property")}

But only when the table is empty.
I will do this after the migration is complete and the temporary triggers have executed.

[mbrandonw]

Hi @StewartLynch, the simplest way would be to perform two queries in a single transaction:

try await database.write { db in 
  guard try Property.fetchCount(db) == 0
  else { return }

  try Property.insert { Property.Draft(…) }
    .execute(db)
}

But it's also possible to do it as a single query using an "INSERT … SELECT … WHERE …", but honestly not sure it's worth the extra work when the above is already quite simple.

[StewartLynch]

I get this error when I use this code:

Value of type 'Property.Type' has no dynamic member 'fetchCount' using key path from root type 'Property.TableColumns'

[mbrandonw]

Ah sorry, that is something that was added recently but has not yet been released (see #296). We will cut a 1.4 soon that will make it available, but until then you have to do:

guard try Property.all.fetchCount(db) == 0
else { return }

[StewartLynch]

I get different errors now.

try await database.write { db in
    guard try Property.all.fetchCount(db) == 0
    else { return }
    
    try Property.insert{ Property.Draft(name: "New Property")
            .execute(db)
    }
}

produces these errors:

No exact matches in call to static method 'buildExpression'
Instance method 'execute' requires the types 'Property.Draft.QueryValue' (aka 'Property.Draft') and '()' be equivalent

[mbrandonw]

try Property.insert{ Property.Draft(name: "New Property")
.execute(db)
}

It seems you have the closing brace in the incorrect place. It should be .insert { … }.execute(db).

[StewartLynch]

Duh! Sorry, I should have been more careful..