rules_transformer.md

RulesTransformer

Use an ordered set of rules to conditionally transform a value. Behaves like an if / elseif / else block: the first rule whose condition matches is applied, and the input is returned unchanged if no rule matches.

Conditions are ExpressionLanguage expressions. By default, the input is available as the value variable. With use_value_as_variables: true, the input (which must then be an array) is used as the set of variables; expression_variables must then list these variable names. expression_variables can also be set to null to disable parsing at initialization (more flexible, but slower).

Transformer reference

• Service: CleverAge\ProcessBundle\Transformer\RulesTransformer
• Transformer code: rules

Accepted inputs

any, or an array of variable name => value when use_value_as_variables is true.

Possible outputs

any: the result of the matching rule (null, a constant, or the result of its transformers), or the input itself if no rule matches.

Options

Code	Type	Required	Default	Description
rules_set	array	X		Ordered list of rules, see below
use_value_as_variables	bool		false	Use the input array as the expression variables, instead of a single value variable
expression_variables	array|null		[value]	Variable names used to parse conditions when options are resolved. null defers parsing to evaluation

Each rule of rules_set has the following options:

Code	Type	Required	Default	Description
condition	string|null		null	Expression; the rule matches if it is truthy
default	bool		false	Mark the rule as the default one (always matches). It cannot have a condition, no conditional rule may follow it, only one allowed
set_null	bool		false	If true, return null (takes precedence on constant and transformers)
constant	any		null	If not null, return this value (takes precedence on transformers)
transformers	array		[]	Transformers applied on the input, see TransformerTrait. With no transformer, the input is returned

A rule without condition and without default: true never matches.

Examples

• Rules on the value variable, with a default rule

# Transformer options level
rules:
  rules_set:
    - condition: 'value["order"]["origin"] === "marketplace"'
      transformers:
        property_accessor:
          property_path: '[customer][id]'
    - condition: 'value["order"]["origin"] === "e-commerce"'
      constant: value1234
    - default: true
      set_null: true

• Same rules, using the input keys as variables (transformers still receive the whole input)

# Transformer options level
rules:
  use_value_as_variables: true
  expression_variables: [order, customer]
  rules_set:
    - condition: 'order["origin"] === "marketplace"'
      transformers:
        property_accessor:
          property_path: '[customer][id]'
    - condition: 'order["origin"] === "e-commerce"'
      constant: variable1234
    - default: true
      set_null: true

Notes

Conditions are parsed with the bundle's cleverage_process.expression_language service, which also exposes the PHP preg_match function.