DA.Record

Exports the record machinery necessary to allow one to annotate code that is polymorphic in the underlying record type.

Module Snapshot

Lifecycle

Stable.

Notices

Status: active Introduced in: 3.4.9 Removed in: - Warnings: 0 Deprecations: 0 Deprecated since: -

Data Types

`type HasField x r a`

= (GetField x r a, SetField x r a) HasField is a class synonym for GetField and SetField, which respectively give you getter and setter functions for each record field automatically. In the vast majority of use-cases, plain Record syntax should be preferred:

daml> let a = MyRecord 1 "hello"
daml> a.foo
1
daml> a.bar
"hello"
daml> a { bar = "bye" }
MyRecord {foo = 1, bar = "bye"}
daml> a with foo = 3
MyRecord {foo = 3, bar = "hello"}
daml>

For more on Record syntax, see https://docs.digitalasset.com/build/3.4/reference/daml/stdlib/DA-Record.html. GetField x r a and SetField x r a are typeclasses taking three parameters. The first parameter x is the field name, the second parameter r is the record type, and the last parameter a is the type of the field in this record. For example, if we define a type:

data MyRecord = MyRecord with
    foo : Int
    bar : Text

Then we get, for free, the following GetField and SetField instances:

GetField "foo" MyRecord Int
SetField "foo" MyRecord Int
GetField "bar" MyRecord Text
SetField "bar" MyRecord Text

If we want to get a value, we can use the getField method of class GetField:

getFoo : MyRecord -> Int
getFoo r = getField @"foo" r

getBar : MyRecord -> Text
getBar r = getField @"bar" r

Note that this uses the “type application” syntax ( f @t ) to specify the field name. Likewise, if we want to set the value in the field, we can use the setField method of class SetField:

setFoo : Int -> MyRecord -> MyRecord
setFoo a r = setField @"foo" a r

setBar : Text -> MyRecord -> MyRecord
setBar a r = setField @"bar" a r

Typeclasses

`class GetField x r a`

GetField x r a provides the getter part of HasField Methods:

getField : r -> a

Instances:

instance GetField _1 (a, b) a
instance GetField _1 (a, b, c) a
instance GetField _1 (a, b, c, d) a
instance GetField _1 (a, b, c, d, e) a
instance GetField _2 (a, b) b
instance GetField _2 (a, b, c) b
instance GetField _2 (a, b, c, d) b
instance GetField _2 (a, b, c, d, e) b
instance GetField _3 (a, b, c) c
instance GetField _3 (a, b, c, d) c
instance GetField _3 (a, b, c, d, e) c
instance GetField _4 (a, b, c, d) d
instance GetField _4 (a, b, c, d, e) d
instance GetField _5 (a, b, c, d, e) e
instance GetField appEndo (Endo a) (a -> a)
instance GetField category FailureStatus FailureCategory
instance GetField errorId FailureStatus Text
instance GetField getAll All Bool
instance GetField getAny Any Bool
instance GetField getAnyView AnyView Any
instance GetField getAnyViewInterfaceTypeRep AnyView InterfaceTypeRep
instance GetField hd (NonEmpty a) a
instance GetField map (Set k) (Map k ())
instance GetField message FailureStatus Text
instance GetField message ArithmeticError Text
instance GetField message AssertionFailed Text
instance GetField message GeneralError Text
instance GetField message PreconditionFailed Text
instance GetField meta FailureStatus (TextMap Text)
instance GetField runState (State s a) (s -> (a, s))
instance GetField srcLocEndCol SrcLoc Int
instance GetField srcLocEndLine SrcLoc Int
instance GetField srcLocFile SrcLoc Text
instance GetField srcLocModule SrcLoc Text
instance GetField srcLocPackage SrcLoc Text
instance GetField srcLocStartCol SrcLoc Int
instance GetField srcLocStartLine SrcLoc Int
instance GetField tl (NonEmpty a) [a]

`class SetField x r a`

SetField x r a provides the setter part of HasField Methods:

setField : a -> r -> r

Instances:

instance SetField _1 (a, b) a
instance SetField _1 (a, b, c) a
instance SetField _1 (a, b, c, d) a
instance SetField _1 (a, b, c, d, e) a
instance SetField _2 (a, b) b
instance SetField _2 (a, b, c) b
instance SetField _2 (a, b, c, d) b
instance SetField _2 (a, b, c, d, e) b
instance SetField _3 (a, b, c) c
instance SetField _3 (a, b, c, d) c
instance SetField _3 (a, b, c, d, e) c
instance SetField _4 (a, b, c, d) d
instance SetField _4 (a, b, c, d, e) d
instance SetField _5 (a, b, c, d, e) e
instance SetField appEndo (Endo a) (a -> a)
instance SetField category FailureStatus FailureCategory
instance SetField errorId FailureStatus Text
instance SetField getAll All Bool
instance SetField getAny Any Bool
instance SetField getAnyView AnyView Any
instance SetField getAnyViewInterfaceTypeRep AnyView InterfaceTypeRep
instance SetField hd (NonEmpty a) a
instance SetField map (Set k) (Map k ())
instance SetField message FailureStatus Text
instance SetField message ArithmeticError Text
instance SetField message AssertionFailed Text
instance SetField message GeneralError Text
instance SetField message PreconditionFailed Text
instance SetField meta FailureStatus (TextMap Text)
instance SetField runState (State s a) (s -> (a, s))
instance SetField srcLocEndCol SrcLoc Int
instance SetField srcLocEndLine SrcLoc Int
instance SetField srcLocFile SrcLoc Text
instance SetField srcLocModule SrcLoc Text
instance SetField srcLocPackage SrcLoc Text
instance SetField srcLocStartCol SrcLoc Int
instance SetField srcLocStartLine SrcLoc Int
instance SetField tl (NonEmpty a) [a]

Ledger API

Daml Standard Library

Daml Script

TypeScript

dApp API

Wallet Gateway

Splice APIs

Admin API

DA.Record

DA.Record

Module Snapshot

Lifecycle

Notices

Data Types

`type HasField x r a`

Typeclasses

`class GetField x r a`

`class SetField x r a`

​DA.Record

​Module Snapshot

Lifecycle

Notices

​Data Types

​type HasField x r a

​Typeclasses

​class GetField x r a

​class SetField x r a

DA.Record

Module Snapshot

Data Types

`type HasField x r a`

Typeclasses

`class GetField x r a`

`class SetField x r a`