Database.PostgreSQL.Entity.Types

An Entity stores the following information about the structure of a database table:

• Its name

• Its primary key

• The fields it contains

Example

data ExampleEntity = E
  { key    :: Key
  , field1 :: Int
  , field2 :: Bool
  }
  deriving stock (Eq, Show, Generic)
  deriving anyclass (FromRow, ToRow)
  deriving Entity
     via (GenericEntity '[TableName "entities"] ExampleEntity)

When using the functions provided by this library, you will sometimes need to be explicit about the Entity you are referring to.

A wrapper for table fields.

A quasi-quoter for safely constructing Fields.

Example:

instance Entity BlogPost where
  tableName  = "blogposts"
  primaryKey = [field| blogpost_id |]
  fields = [ [field| blogpost_id |]
           , [field| author_id |]
           , [field| uuid_list :: uuid[] |] -- ← This is where we specify an optional PostgreSQL type annotation
           , [field| title |]
           , [field| content |]
           , [field| created_at |]
           ]

Get the name of a field.

Get the type of a field, if any.

Wrapper used by the update function in order to have the primary key as the last parameter passed, since it appears in the WHERE clause.

Term-level options

Type-level options for Deriving Via

Contains a list of TextModifiers modifiers

The modifiers that you can apply to the fields:

• StripPrefix

• CamelTo, and its variations

• CamelToSnake

• CamelToKebab

TextModifier to remove a certain prefix from the fields

FieldModifier taking a separator Char when transforming from CamelCase.

CamelCase to snake_case

CamelCase to kebab-case