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DA.Record

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

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Module Snapshot

Lifecycle

Stable.

Notices

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

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Data Types

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type HasField = (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

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Typeclasses

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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]

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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]