Transient attributes

A transient attribute is visible inside the factory (to dynamic blocks, overrides, and callbacks) but is not passed to the model constructor and is not returned by attributes-for. Use them for "knobs" — flags or inputs that shape how the real attributes get computed, without polluting the model itself.

Declaring

Wrap the declarations in a .transient block:

define {
  .factory: 'greeting', {
    .transient: {
      .upcase: False;
      .who:    'World';
    };

    .text: { .upcase ?? "HELLO, {.who.uc}" !! "Hello, {.who}" };
  };
};

Inside .transient, every attribute capture (static, dynamic, or add-attribute) is marked transient. Attributes outside the block are normal persisted attributes.

Visibility

Transient values are first-class to the evaluator. Dynamic attributes and callbacks see them via the leading-dot shorthand:

ORM::Factory.build('greeting').text;                       # 'Hello, World'
ORM::Factory.build('greeting', :who<Greg>).text;           # 'Hello, Greg'
ORM::Factory.build('greeting', :upcase(True)).text;        # 'HELLO, WORLD'

Overrides for a transient flow through to anything that depends on it.

Excluded from the model and attributes-for

The model constructor never sees transient values — Greeting.new above is called with only text => ..., never upcase or who. Likewise:

ORM::Factory.attributes-for('greeting');                   # { text => 'Hello, World' }

attributes-for is the canonical "what does this factory produce as data" view, so it follows the same exclusion.