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# Fields

Fields define the behavior of the data on model’s record.

## Field options

The following arguments are available to all field types. All are optional except `Field.string`.

### `string`

`Field.``string`

A string for the label of the field.

### `help`

`Field.``help`

A multi-line help string for the field.

### `required`

`Field.``required`

If `True`, the field is not allowed to be empty. Default is `False`.

### `readonly`

`Field.``readonly`

If `True`, the field is not editable in the client. Default is `False`.

### `domain`

`Field.``domain`

A domain constraint that will be applied on the field value.

Warning

For now it only works on relational fields like `Many2One`, `One2Many` and `Many2Many`.

### `states`

`Field.``states`

A dictionary that defines dynamic states of the field and overrides the static one. Possible keys are `required`, `readonly` and `invisible`. The values are `PYSON` statements that will be evaluated with the values of the record.

### `select`

`Field.``select`

If true, the content of the field will be indexed.

### `on_change`

`Field.``on_change`

A list of field names. If this attribute is set, the client will call the method `on_change_<field name>` of the model when the user changes the current field value and will give the values of each fields in this list. The method signature is:

    on_change_<field name>()

This method must return a dictionary with the values of fields to be updated.

Note

The on_change_<field name> methods are runnin in a rollbacked transaction.

### `on_change_with`

`Field.``on_change_with`

A list of field names. Same like `on_change`, but defined the other way around. If this attribute is set, the client will call the method `on_change_with_<field name>` of the model when the user changes one of the fields defined in the list and will give the values of each fields in this list. The method signature is:

    on_change_with_<field name>()

This method must return the new value of the field.

Note

The on_change_with_<field name> methods are running in a rollbacked transaction.

### `depends`

`Field.``depends`

A list of field names on which the current one depends. This means that the client will also read these fields even if they are not defined on the view. `Field.depends` is used per example to ensure that `PYSON` statement could be evaluated.

### `context`

`Field.``context`

A dictionary which will update the current context when opening a relation field.

### `loading`

`Field.``loading`

Define how the field must be loaded: `lazy` or `eager`.

### `name`

`Field.``name`

The name of the field.

Instance methods:

`Field.``convert_domain`(domain, tables, Model)

  Convert the simple domain clause into a SQL expression or a new domain.

Where `tables` is a nested dictionary containing the existing joins (and it could be updated to add new joins):

    {
        None: (<Table invoice>, None),
        'party': {
            None: (<Table party>, <join_on sql expression>),
            'addresses': {
                None: (<Table address>, <join_on sql expression>),
                },
            },
        }

`Field.``sql_format`(value)

  Convert the value to use as parameter of SQL queries.

`Field.``sql_type`()

  Return the namedtuple(‘SQLType’, ‘base type’) which defines the SQL type to use for creation and casting.

## Default value

See default value

## Ordering

A class method could be defined for each field which must return a list of SQL expression on which to order instead of the field. The method signature is:

    order_<field name>(tables)

Where `tables` is a nested dictionary, see `convert_domain()`.

## Field types

### Boolean

class `trytond.model.fields.``Boolean`(string[, **options])

A true/false field.

### Integer

class `trytond.model.fields.``Integer`(string[, **options])

An integer field.

### BigInteger

class `trytond.model.fields.``BigInteger`(string[, **options])

A long integer field.

### Char

class `trytond.model.fields.``Char`(string[, size[, translate[, **options]]])

A single line string field.

`Char` has two extra optional arguments:

`Char.``size`

  The maximum length (in characters) of the field. The size is enforced at the storage level and in the client input.

`Char.``translate`

  If true, the value of the field is translatable. The value readed and stored will depend on the `language` defined in the context.

`Char.``autocomplete`

  A list of field names. If this attribute is set, the client will call the method `autocomplete_<field name>` of the model when the user changes one of those field value. The method signature is:

      autocomplete_<field name>(values)

  This method must return a list of string that will populate the ComboboxEntry in the client.

### Sha

class `trytond.model.fields.``Sha`(string[, **options])

A string field which value will be stored with a secure hash algorithm.

### Text

class `trytond.model.fields.``Text`(string[, size[, translatable[, **options]]])

A multi line string field.

`Text` has two extra optional arguments:

`Text.``size`

  Same as `Char.size`

`Text.``translate`

  Same as `Char.translate`

### Float

class `trytond.model.fields.``Float`(string[, digits[, **options]])

A floating-point number field. It will be represented in Python by a `float` instance.

`Float` has one extra optional arguments:

`Float.``digits`

  A tuple of two integers. The first integer defines the total of numbers in the integer part. The second integer defines the total of numbers in the decimal part. Integers can be replaced by a `PYSON` statement.

### Numeric

class `trytond.model.fields.``Numeric`(string[, digits[, **options]])

A fixed-point number field. It will be represented in Python by a `decimal.Decimal` instance.

`Numeric` has one extra optional arguments:

`Numeric.``digits`

  Same as `Float.digits`

### Date

class `trytond.model.fields.``Date`(string[, **options])

A date, represented in Python by a `datetime.date` instance.

### DateTime

class `trytond.model.fields.``DateTime`(string[, format, **options])

A date and time, represented in Python by a `datetime.datetime` instance.

`DateTime.``format`

  A string format as used by strftime. This format will be used to display the time part of the field. The default value is %H:%M:%S. The value can be replaced by a `PYSON` statement.

### Timestamp

class `trytond.model.fields.``Timestamp`(string[, **options])

A timestamp, represented in Python by a `datetime.datetime` instance.

### Time

class `trytond.model.fields.``Time`(string[, format, **options])

A time, represented in Python by a `datetime.time` instance.

`Time.``format`

  Same as `DateTime.format`

### Binary

class `trytond.model.fields.``Binary`(string[, **options])

A binary field. It will be represented in Python by a `str` instance.

`Binary` has one extra optional argument:

`Binary.``filename`

  Name of the field that holds the data’s filename. Default value is an empty string, which means the data has no filename (in this case, the filename is hidden, and the “Open” button is hidden when the widget is set to “image”).

### Selection

class `trytond.model.fields.``Selection`(selection, string[, sort[, selection_change_with[, translate[, **options]]])

A string field with limited values to choice.

`Selection` has one extra required argument:

`Selection.``selection`

  A list of 2-tuples that looks like this:

      [
          ('M', 'Male'),
          ('F', 'Female'),
      ]

  The first element in each tuple is the actual value stored. The second element is the human-readable name.

  It can also be the name of a class method on the model, that will return an appropriate list. The signature of the method is:

      selection()

  Note

  The method is automaticly added to `trytond.model.Model._rpc` if not manually set.

`Selection` has two extra optional arguments:

`Selection.``sort`

  If true, the choices will be sorted by human-readable value. Default value is `True`.

`Selection.``selection_change_with`

  A list of field names. If this attribute is set, the client will call the `selection` method of the model when the user changes on of the fields defined in the list and will give the values of each fields in the list. The `selection` method should be an instance method.

`Selection.``translate_selection`

  If true, the human-readable values will be translated. Default value is `True`.

### Reference

class `trytond.model.fields.``Reference`(string[, selection[, selection_change_with[, **options]])

A field that refers to a record of a model. It will be represented in Python by a `str` instance like this:

    '<model name>,<record id>'

But a `tuple` can be used to search or set value.

`Reference` has one extra optional argument:

`Reference.``selection`

  Same as `Selection.selection` but only for model name.

`Reference.``selection_change_with`

Same like `Selection.selection_change_with`.

### Many2One

class `trytond.model.fields.``Many2One`(model_name, string[, left[, right[, ondelete[, datetime_field[, **options]]]]])

A many-to-one relation field.

`Many2One` has one extra required argument:

`Many2One.``model_name`

  The name of the target model.

`Many2One` has some extra optional arguments:

`Many2One.``left`

  The name of the field that stores the left value for the Modified Preorder Tree Traversal. It only works if the `model_name` is the same then the model.

`Many2One.``right`

  The name of the field that stores the right value. See `left`.

`Many2One.``ondelete`

  Define the behavior of the record when the target record is deleted. Allowed values are:

  > - `CASCADE`: it will try to delete the record.
  > - `RESTRICT`: it will prevent the deletion of the target record.
  > - `SET NULL`: it will empty the relation field.

  `SET NULL` is the default setting.

  Note

  `SET NULL` will be override into `RESTRICT` if `required` is true.

`Many2One.``datetime_field`

  If set, the target record will be read at the date defined by the datetime field name of the record. It is usually used in combination with `trytond.model.ModelSQL._history` to request a value for a given date and time on a historicized model.

### One2Many

class `trytond.model.fields.``One2Many`(model_name, field, string[, add_remove[, order[, datetime_field[, size[, **options]]]]])

A one-to-many relation field. It requires to have the opposite `Many2One` field or a `Reference` field defined on the target model.

This field accepts as written value a list of tuples like this:

> - `('create', [{<field name>: value, ...}, ...])`: it will create new target records and link them to this one.
> - `('write'[, ids, ...], {<field name>: value, ...})`: it will write values to target ids.
> - `('delete'[, ids, ...])`: it will delete the target ids.
> - `('delete_all')`: it will delete all the target records.
> - `('add'[, ids, ...])`: it will link the target ids to this record.
> - `('unlink'[, ids, ...])`: it will unlink the target ids from this record.
> - `('unlink_all')`: it will unlink all the target records.
> - `('set'[, ids, ...])`: it will link only the target ids to this record.

`One2Many` has some extra required arguments:

`One2Many.``model_name`

  The name of the target model.

`One2Many.``field`

  The name of the field that handles the opposite `Many2One` or `Reference`.

`One2Many` has some extra optional arguments:

`One2Many.``add_remove`

  A domain to select records to add. If set, the client will allow to add/remove existing records instead of only create/delete.

`One2Many.``order`

  A list of tuple defining the default order of the records like for `trytond.model.ModelSQL._order`.

`One2Many.``datetime_field`

  Same as `Many2One.datetime_field`

`One2Many.``size`

  An integer or a PYSON expression denoting the maximum number of records allowed in the relation.

### Many2Many

class `trytond.model.fields.``Many2Many`(relation_name, origin, target, string[, order[, datetime_field[, size[, **options]]]])

A many-to-many relation field.

`Many2Many` has some extra required arguments:

`Many2Many.``relation_name`

  The name of the relation model.

`Many2Many.``origin`

  The name of the field that has the `Many2One` or `Reference` to the record.

`Many2Many.``target`

  The name of the field that has the `Many2One` to the target record.

Note

A `Many2Many` field can be used on a simple `ModelView`, like in a `Wizard`. For this, `relation_name` is set to the target model and `origin` and `target` are set to None.

`Many2Many` has some extra optional arguments:

`Many2Many.``order`

  Same as `One2Many.order`

`Many2Many.``datetime_field`

  Same as `Many2One.datetime_field`

`Many2Many.``size`

  An integer or a PYSON expression denoting the maximum number of records allowed in the relation.

Instance methods:

`Many2Many.``get_target`()

  Return the target `Model`.

### One2One

class `trytond.model.fields.``One2One`(relation_name, origin, target, string[, datetime_field[, **options]])

A one-to-one relation field.

Warning

It is on the relation_name `Model` that the unicity of the couple (origin, target) must be checked.

`One2One.``datetime_field`

  Same as `Many2One.datetime_field`

Instance methods:

`One2One.``get_target`()

  Return the target `Model`.

### Function

class `trytond.model.fields.``Function`(field, getter[, setter[, searcher]])

A function field can emulate any other given field.

`Function` has a required argument:

`Function.``getter`

  The name of the classmethod or instance of the `Model` for getting values. The signature of the classmethod is:

      getter(instances, name)

  where name is the name of the field, and it must return a dictionary with a value for each instance.

  Or the signature of the classmethod is:

      getter(instances, names)

  where names is a list of name fields, and it must return a dictionary containing for each names a dictionary with a value for each instance.

  The signature of the instancemethod is:

      getter(name)

  where name is the name of the field, and it must return the value.

`Function` has some extra optional arguments:

`Function.``setter`

  The name of the classmethod of the `Model` to set the value. The signature of the method id:

      setter(ids, name, value)

  where name is the name of the field and value the value to set.

`Function.``searcher`

  The name of the classmethod of the `Model` to search on the field. The signature of the method is:

      searcher(name, clause)

  where name is the name of the field and clause is a domain clause. It must return a list of domain clauses but the `operand` can be a SQL query.

Instance methods:

`Function.``get`(ids, model, name[, values])

  Call the `getter` classmethod where model is the `Model` instance of the field, name is the name of the field.

`Function.``set`(ids, model, name, value)

  Call the `setter` classmethod where model is the `Model` instance of the field, name is the name of the field, value is the value to set.

`Function.``search`(model, name, clause)

  Call the `searcher` classmethod where model is the `Model` instance of the field, name is the name of the field, clause is a clause of domain.

### Property

class `trytond.model.fields.``Property`(field)

A property field that is like a `Function` field but with predifined `getter`, `setter` and `searcher` that use the `ModelSQL` ir.property to store values.

Instance methods:

`Property.``get`(ids, model, name[, values])

  Same as `Function.get()`.

`Property.``set`(ids, model, name, value)

  Same as `Function.set()`.

`Property.``search`(model, name, clause)

  Same as `Function.search()`.

### Dict

class `trytond.model.fields.``Dict`(schema_model[, **options])

A dictionary field with predefined keys.

`Dict` has one extra required argument:

`Dict.``schema_model`

  The name of the `DictSchemaMixin` model that stores the definition of keys.

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