Calculated default values

Synopsis

A value can be calculated. In this case we have four possibilities:

calculation via Jinja
calculation via a variable
calculation via information
calculation via a suffix: in the case of a variable in a dynamic family
calculation via an index: in the case of a follower variable

If the user modifies the value of the variable, the default value is no longer used, so the calculation is no longer carried out. This is also the case if the variable has the auto_save attribute.

On the other hand, if the variable is hidden (with the hidden parameter), it is the default value that is used and not the value customized by the user.

Note

A follower variable cannot be calculated automatically.

Parameters

Depending on the types of calculation, the parameters will be different:

Calculation type	Parameter	Comments	Sample
	type `string` `mandatory`	Type of calculation, possible values are: jinja, variable, information, suffix or index	jinja
Jinja	jinja `string` `mandatory`	Template Jinja. For a multiple variable, each line represents a value.	`{% if rougail.variable %} {{ rougail.variable }} {% endif %}`
Jinja	params `list`	Additional parameters passed to the Jinja template
Variable (`mandatory`) Information	variable `string`	Name of associated variable	rougail.variable
Variable	propertyerror `boolean`	If access to the variable is not possible due to a property (for example `disabled`) by default an error is returned. If the attribute is `false`, the calculated value is empty. Default value: `true`	false
Information	information `string` `mandatory`	Name of the information whose value we want to retrieve.	doc

In the case of a Jinja type calculation, it is possible to have parameters.

There are two types of parameter:

the standard parameters (string, boolean, integer, null), in this case just do: “key: value”
the advanced settings:
- parameter via a variable
- parameter via an information
- parameter via a suffix: in the case of a variable in a dynamic family
- parameter via an index: in the case of a follower variable

Parameter type	Parameter	Comments	Sample
	name `string` `mandatory`	parameter’s name	my_param
	type `string` `mandatory`	parameter’s type, possible values are: variable, information, suffix or index	suffix
Variable	variable `string` `mandatory`	Variable’s name	rougail.variable
Variable (`mandatory`) information	propertyerror `boolean`	If access to the variable is not possible due to a property (for example `disabled`) by default an error is returned. If the attribute is `False`, the parameter is not passed to the Jinja template.	Default value: `True`
Variable	optional `boolean`	The variable may not exist depending on YAML file imports. If the optional parameter is `True`, the parameter will simply be deleted if the variable does not exist. Default value : `False`	True
Information	information `string` `mandatory`	Name of the information whose value we want to retrieve.	doc

Examples

Calculation via a Jinja template

Let’s start with an example from a simple Jinja template:

---
version: '1.0'
my_calculated_variable:
  default:
    type: jinja
    jinja: 'no'

Here is a second example with a boolean variable:

---
version: '1.0'
my_calculated_variable:
  type: boolean
  default:
    type: jinja
    jinja: 'false'

And a multiple value of the number type:

---
version: '1.0'
my_calculated_variable:
  type: number
  multi: true
  default:
    type: jinja
    jinja: |
      1
      2
      3

Let’s create a variable whose value is returned by a python function:

---
version: '1.0'
my_calculated_variable:
  default:
    type: jinja
    jinja: '{{ return_no() }}'

Then let’s create the return_no function:

def return_no():
    return 'no'

An example with parameters:

---
version: '1.0'
my_calculated_variable:
  description: my description
  default:
    type: jinja
    jinja: |
            {{ param1 }}{% if param2 is defined %}_{{ param2 }}{% endif %}_{{ param3 }}
    params:
      param1: value
      param2:
        type: variable
        variable: rougail.unknown_variable
        optional: true
      param3:
        type: information
        information: doc
        variable: rougail.my_calculated_variable

An example with a suffix type parameter:

---
version: '1.0'
varname:
  multi: true
  default:
    - val1
    - val2
my_dyn_family_:
  type: dynamic
  variable: rougail.varname
  description: 'Describe '
  my_dyn_var:
    type: string
    default:
      type: jinja
      jinja: 'the suffix is: {{ param1 }}'
      params:
        param1:
          type: suffix

In this example, we see a dynamic family. Two families will be created: rougail.my_dyn_family_val1.my_dyn_var and rougail.my_dyn_family_val2.my_dyn_var.

The value of the variable inside this family ‘this suffix is: ‘ + the value of the suffix (val1 and val2 respectively).

An example with an index type parameter:

---
version: '1.0'
family:
  type: leadership
  leader:
    multi: true
    default:
      - val1
      - val2
  follower1:
    default:
      type: jinja
      jinja: 'the index is: {{ param1 }}'
      params:
        param1:
          type: index

Calculation via a variable

Copy a variable in another:

---
version: '1.0'
my_variable:
  multi: true
  default:
    - val1
    - val2
my_calculated_variable:
  multi: true
  default:
    type: variable
    variable: rougail.my_variable

Copy one variable to another if the source has no property problem:

---
version: '1.0'
my_variable:
  default: val1
  disabled: true
my_calculated_variable:
  multi: true
  default:
    type: variable
    variable: rougail.my_variable
    propertyerror: false

Copy two non-multiple variables into a multiple variable:

---
version: '1.0'
my_variable_1:
  default: val1
my_variable_2:
  default: val2
my_calculated_variable:
  multi: true
  default:
    - type: variable
      variable: rougail.my_variable_1
    - type: variable
      variable: rougail.my_variable_2

A variable in a dynamic family can also be used in a calculation.

For example using the variable for a particular suffix:

---
version: '1.0'
varname:
  multi: true
  default:
    - val1
    - val2
my_dyn_family_:
  type: dynamic
  variable: rougail.varname
  description: 'Describe '
  my_dyn_var_:
    type: string
    default:
      type: suffix
all_dyn_var:
  default:
    type: variable
    variable: rougail.my_dyn_family_val1.my_dyn_var_val1

In this case, we recover the value val1.

Second example using the variable for all suffixes:

---
version: '1.0'
varname:
  multi: true
  default:
    - val1
    - val2
my_dyn_family_:
  type: dynamic
  variable: rougail.varname
  description: 'Describe '
  my_dyn_var_:
    type: string
    default:
      type: suffix
all_dyn_var:
  multi: true
  default:
    type: variable
    variable: rougail.my_dyn_family_.my_dyn_var_

In this case, we recover the val1 and val2 list.

Calculation via a suffix

---
version: '1.0'
varname:
  multi: true
  default:
    - val1
    - val2
my_dyn_family_:
  type: dynamic
  variable: rougail.varname
  description: 'Describe '
  my_dyn_var_:
    type: string
    default:
      type: suffix

Calculation via an index

---
version: '1.0'
family:
  type: leadership
  leader:
    multi: true
    default:
      - val1
      - val2
  follower1:
    type: number
    default:
      type: index

Redefinition

In a first dictionary, let’s declare our variable and our calculation:

---
version: '1.0'
my_calculated_variable:
  default:
    type: jinja
    jinja: 'the value is calculated'

In a second dictionary, it is possible to redefine the calculation:

---
version: '1.0'
my_calculated_variable:
  redefine: true
  default:
    type: jinja
    jinja: 'the value is redefined'

In a third dictionary, we even can delete the calculation if needed:

---
version: '1.0'
my_calculated_variable:
  redefine: true
  default: null