Injects the plumbing that lets an Ecto.Schema be backed by a Google Spreadsheet list (tab).

Usage

defmodule MyApp.Account do
  use EctoGSS.Schema, {
    :model,
    columns: ["A", "Y"],
    list: "All Accounts",
    spreadsheet: "1h85keViqbRzgTN245gEw5s9roxpaUtT7i-mNXQtT8qQ"
  }

  use Ecto.Schema

  schema "accounts" do
    field(:nickname, EctoGSS.Schema.AllAccounts.A)
    field(:email, EctoGSS.Schema.AllAccounts.Y)
  end
end

use EctoGSS.Schema, {:model, opts} generates, at compile time:

• one Ecto.Type module per entry in columns:, named EctoGSS.Schema.<ListNameWithoutSpaces>.<Column> (spaces in list: are stripped to build the module name, e.g. list "All Accounts" and column "A" produce EctoGSS.Schema.AllAccounts.A). Each generated type module knows the spreadsheet column letter it maps to and is meant to be used as the type of a field in the host schema's own schema/2 block;
• spreadsheet/0, list/0 and gss_schema/0 functions injected into the host schema module, used by EctoGSS.Repo to locate the backing sheet and mark the module as a GSS-backed schema.

Locating the spreadsheet

There are two ways to tell EctoGSS.Repo which spreadsheet and list to use:

• pass spreadsheet: (and list:) explicitly in opts, as shown above; or
• omit spreadsheet: and instead rely on the host schema's @schema_prefix to supply the spreadsheet id: EctoGSS.Repo falls back to __schema__(:prefix) whenever spreadsheet/0 returns nil.

list: has no such fallback and is always required: omitting it raises ArgumentError when use EctoGSS.Schema, {:model, opts} expands.

Compile-time vs. runtime option

list: and columns: must be compile-time literals: they are used to name the generated Ecto.Type modules while this macro is expanding, so their values must be known then. spreadsheet:, on the other hand, is only unquoted into the generated spreadsheet/0 function body and may be any expression valid in the host module (e.g. a module attribute or a call).