A fact of a feed's schema in a design (spec/14 §7.4, D-136).
Visualize.Chart.fact/3 builds one: the attribute key of field in the schema bound
to slot source — a field's label, its unit, the order of its states. The term is
allowed wherever a value can appear, and in a text as the hole
#{fact(:source, :field, :key)}; Visualize.Chart.apply/2 replaces it by the
attribute, as it replaces a variable by its value. Reading a fact is a requirement: a
schema that does not give the attribute fails application, naming the slot, the field
and the attribute.
The keys are keys/0: the attributes of Visualize.Data.Schema.attributes/0 and two
derived from a field's declared values, :names and :colors (D-225). fetch/3 says
what a key gives, and shape/1 what shape it is: a :scalar, a :list or a :map.
Only a scalar is a word (word?/1), so only a scalar key's fact is a text's hole.
Examples
iex> Visualize.Chart.fact(:primary, :latency, :unit)
%Visualize.Chart.Fact{source: "primary", field: "latency", key: :unit}Summary
Functions
What the fact key key gives field in schema (spec/14 §7.4, D-225): {:ok, value},
or :error when it gives nothing.
The fact keys, in order: the description attributes, then :names and :colors
(spec/14 §7.4, D-225).
The shape of the fact key key's value, whatever schema gives it (spec/14 §7.4):
:scalar, :list or :map.
Whether a fact of the key key is written as a word — its shape is :scalar — and so
may stand in a text's hole (spec/14 §7.4). A list or a map is not a word.
Types
Functions
@spec fetch(Visualize.Data.Schema.t(), Visualize.Data.Schema.name(), atom()) :: {:ok, term()} | :error
What the fact key key gives field in schema (spec/14 §7.4, D-225): {:ok, value},
or :error when it gives nothing.
An attribute is the description's as written, except :values, which is the bare
values (Visualize.Data.Schema.values/2). :names and :colors are the maps of
Visualize.Data.Schema.value_names/2 and value_colors/2, given when not empty.
iex> schema = Visualize.Data.Schema.new!(%{state: %{type: :category, values: [
...> %{value: "ok", name: "OK"}, %{value: "down", color: "#c62828"}, "unknown"]}})
iex> Visualize.Chart.Fact.fetch(schema, :state, :values)
{:ok, ["ok", "down", "unknown"]}
iex> Visualize.Chart.Fact.fetch(schema, "state", :names)
{:ok, %{"ok" => "OK"}}
iex> Visualize.Chart.Fact.fetch(schema, :state, :colors)
{:ok, %{"down" => "#c62828"}}
iex> Visualize.Chart.Fact.fetch(schema, :state, :unit)
:error@spec keys() :: [atom(), ...]
The fact keys, in order: the description attributes, then :names and :colors
(spec/14 §7.4, D-225).
iex> Visualize.Chart.Fact.keys() |> Enum.take(-3)
[:values, :names, :colors]The shape of the fact key key's value, whatever schema gives it (spec/14 §7.4):
:scalar, :list or :map.
iex> Visualize.Chart.Fact.shape(:unit)
:scalar
iex> Visualize.Chart.Fact.shape(:values)
:list
iex> Visualize.Chart.Fact.shape(:names)
:mapWhether a fact of the key key is written as a word — its shape is :scalar — and so
may stand in a text's hole (spec/14 §7.4). A list or a map is not a word.
iex> Visualize.Chart.Fact.word?(:label)
true
iex> Visualize.Chart.Fact.word?(:order)
false