Working with models

Models are Yaml files used to define serializable classes in Serverpod. They are used to generate Dart code for the server and client, and, if a database table is defined, to generate database code for the server. Using regular .yaml files within lib/src/models is supported, but it is recommended to use .spy.yaml (.spy stands for "Serverpod YAML") to leverage syntax highlighting provided by the Serverpod Extension for VS Code.

The files are analyzed by the Serverpod CLI when generating the project and creating migrations.

Run serverpod generate to generate dart classes from the model files.

Class

class: Company
fields:
  name: String
  foundedDate: DateTime?
  employees: List<Employee>

Supported types are bool, int, double, String, Duration, DateTime, ByteData, UuidValue, and other serializable classes, exceptions and enums. You can also use Lists and Maps of the supported types, just make sure to specify the types. Null safety is supported. Once your classes are generated, you can use them as parameters or return types to endpoint methods.

Limiting visibility of a generated class

By default, generated code for your serializable objects is available both on the server and the client. You may want to have the code on the server side only. E.g., if the serializable object is connected to a database table containing private information.

To make a serializable class generated only on the server side, set the serverOnly property to true.

class: MyPrivateClass
serverOnly: true
fields:
  hiddenSecretKey: String

It is also possible to set a scope on a per-field basis. By default all fields are visible to both the server and the client. The available scopes are all, serverOnly, none.

info

none is not typically used in serverpod apps. It is intended for the serverpod framework, itself.

class: SelectivelyHiddenClass
fields:
  hiddenSecretKey: String, scope=serverOnly
  publicKey: String

info

Serverpod's models can easily be saved to or read from the database. You can read more about this in the Database section.

Exception

The Serverpod models supports creating exceptions that can be thrown in endpoints by using the exception keyword. For more in-depth description on how to work with exceptions see Error handling and exceptions.

exception: MyException
fields:
  message: String
  errorType: MyEnum

Enum

It is easy to add custom enums with serialization support by using the enum keyword.

enum: Animal
values:
 - dog
 - cat
 - bird

By default the serialization will convert the enum to an int representing the index of the value. Changing the order may therefore have unforeseen consequences when reusing old data (such as from a database). Changing the serialization to be based on the name instead of index is easy.

enum: Animal
serialized: byName
values:
 - dog
 - cat
 - bird

serialized has two valid values byName and byIndex. When using byName the string literal of the enum is used, when using byIndex the index value (0, 1, 2, etc) is used.

info

It's recommended to always set serialized to byName in any new Enum models, as this is less fragile and will be changed to the default setting in version 3 of Serverpod.

Adding documentation

Serverpod allows you to add documentation to your serializable objects in a similar way that you would add documentation to your Dart code. Use three hashes (###) to indicate that a comment should be considered documentation.

### Information about a company.
class: Company
fields:
  ### The name of the company.
  name: String

  ### The date the company was founded, if known.
  foundedDate: DateTime?

  ### A list of people currently employed at the company.
  employees: List<Employee>

Generated code

Serverpod generates some convenience methods on the Dart classes.

copyWith

The copyWith method allows for efficient object copying with selective field updates and is available on all generated classes. Here's how it operates:

var john = User(name: 'John Doe', age: 25);
var jane = john.copyWith(name: 'Jane Doe');

The copyWith method generates a deep copy of an object, preserving all original fields unless explicitly modified. It can distinguish between a field set to null and a field left unspecified (undefined). When using copyWith, any field you don't update remains unchanged in the new object.

toJson / fromJson

The toJson and fromJson methods are generated on all models to help with serialization. Serverpod manages all serialization for you out of the box and you will rarely have to use these methods by your self. See the Serialization section for more info.

Custom methods

Sometimes you will want to add custom methods to the generated classes. The easiest way to do this is with Dart's extension feature.

extension MyExtension on MyClass {
  bool isCustomMethod() {
    return true;
  }
}

Default Values

Serverpod supports defining default values for fields in your models. These default values can be specified using three different keywords that determine how and where the defaults are applied:

Keywords

• default: This keyword sets a default value for both the model (code) and the database (persisted data). It acts as a general fallback if more specific defaults aren't provided.
• defaultModel: This keyword sets a default value specifically for the model (the code side). If defaultModel is not provided, the model will use the value specified by default if it's available.
• defaultPersist: This keyword sets a default value specifically for the database. If defaultPersist is not provided, the database will use the value specified by default if it's available.

How priorities work

• For the model (code side): If both defaultModel and default are provided, the model will use the defaultModel value. If defaultModel is not provided, it will fall back to using the default value.
• For the database (persisted data): If both defaultPersist and default are provided, the database will use the defaultPersist value. If defaultPersist is not provided, it will fall back to using the default value.

You can use these default values individually or in combination as needed. It is not required to use all default types for a field.

info

When using default or defaultModel in combination with defaultPersist, it's important to understand how the interaction between these keywords affects the final value in the database.

If you set a default or defaultModel value, the model's field or variable will have a value when it's passed to the database—it will not be null. Because of this, the SQL query will not use the defaultPersist value since the field already has a value assigned by the model. In essence, assigning a default or defaultModel is like directly providing a value to the field, and the database will use this provided value instead of its own default.

This means that defaultPersist only comes into play when the model does not provide a value, allowing the database to apply its own default setting.

Supported default values

Boolean

Type	Keyword	Description
Boolean	true or false	Sets the field to a boolean value, either true or false.

Example:

boolDefault: bool, default=true

DateTime

Type	Keyword	Description
Current Date and Time	now	Sets the field to the current date and time.
Specific UTC DateTime	UTC DateTime string in the format yyyy-MM-dd'T'HH:mm:ss.SSS'Z'	Sets the field to a specific date and time.

Example:

dateTimeDefaultNow: DateTime, default=now
dateTimeDefaultUtc: DateTime, default=2024-05-01T22:00:00.000Z

Double

Type	Keyword	Description
Double	Any double value	Sets the field to a specific double value.

Example:

doubleDefault: double, default=10.5

Duration

Type	Keyword	Description
Specific Duration	A valid duration in the format Xd Xh Xmin Xs Xms	Sets the field to a specific duration value. For example, 1d 2h 10min 30s 100ms represents 1 day, 2 hours, 10 minutes, 30 seconds, and 100 milliseconds.

Example:

durationDefault: Duration, default=1d 2h 10min 30s 100ms

Enum

Type	Keyword	Description
Enum	Any valid enum value	Sets the field to a specific enum value.

Example:

enum: ByNameEnum
serialized: byName
values:
  - byName1
  - byName2

enum: ByIndexEnum
serialized: byIndex
values:
  - byIndex1
  - byIndex2

class: EnumDefault
table: enum_default
fields:
  byNameEnumDefault: ByNameEnum, default=byName1
  byIndexEnumDefault: ByIndexEnum, default=byIndex1

In this example:

• The byNameEnumDefault field will default to 'byName1' in the database.
• The byIndexEnumDefault field will default to 0 (the index of byIndex1).

Integer

Type	Keyword	Description
Integer	Any integer value	Sets the field to a specific integer value.

Example:

intDefault: int, default=10

String

Type	Keyword	Description
String	Any string value	Sets the field to a specific string value.

Example:

stringDefault: String, default='This is a string'

UuidValue

Type	Keyword	Description
Random UUID	random	Generates a random UUID. On the Dart side, Uuid().v4obj() is used. On the database side, gen_random_uuid() is used.
UUID String	A valid UUID version 4 string	Assigns a specific UUID to the field.

Example:

uuidDefaultRandom: UuidValue, default=random
uuidDefaultUuid: UuidValue, default='550e8400-e29b-41d4-a716-446655440000'

Example

class: DefaultValue
table: default_value
fields:
  ### Sets the current date and time as the default value.
  dateTimeDefault: DateTime, default=now

  ### Sets the default value for a boolean field.
  boolDefault: bool, defaultModel=false, defaultPersist=true

  ### Sets the default value for an integer field.
  intDefault: int, defaultPersist=20

  ### Sets the default value for a double field.
  doubleDefault: double, default=10.5, defaultPersist=20.5

  ### Sets the default value for a string field.
  stringDefault: String, default="This is a string", defaultModel="This is a string"

Keywords

Keyword	Note	class	exception	enum
values	A special key for enums with a list of all enum values.			✅
serialized	Sets the mode enums are serialized in			✅
serverOnly	Boolean flag if code generator only should create the code for the server.	✅	✅	✅
table	A name for the database table, enables generation of database code.	✅
managedMigration	A boolean flag to opt out of the database migration system.	✅
fields	All fields in the generated class should be listed here.	✅	✅
type (fields)	Denotes the data type for a field.	✅	✅
scope	Denotes the scope for a field.	✅
persist	A boolean flag if the data should be stored in the database or not can be negated with !persist	✅
relation	Sets a relation between model files, requires a table name to be set.	✅
name	Give a name to a relation to pair them.	✅
parent	Sets the parent table on a relation.	✅
field	A manual specified foreign key field.	✅
onUpdate	Set the referential actions when updating data in the database.	✅
onDelete	Set the referential actions when deleting data in the database.	✅
optional	A boolean flag to make a relation optional.	✅
indexes	Create indexes on your fields / columns.	✅
fields (index)	List the fields to create the indexes on.	✅
type (index)	The type of index to create.	✅
unique	Boolean flag to make the entries unique in the database.	✅
default	Sets the default value for both the model and the database. This keyword cannot be used with relation.	✅
defaultModel	Sets the default value for the model side. This keyword cannot be used with relation.	✅
defaultPersist	Sets the default value for the database side. This keyword cannot be used with relation and !persist.	✅