Flags are how we map python values from our django server to Elm primitives that our programs will be initiated with.
You can think of them as a schema of sorts, that can do a number of extra tasks for us, such as:
- Validate python values
- Generate Elm decoders
You can find a good explanation for djelm flags with examples in the official guide here.
literal : str
StringFlag()
# Match against a literal string
StringFlag(literal="hello")# python
"foo" : str
# elm
"foo" : String
IntFlag()# python
2 : int
# elm
2 : Int
FloatFlag()# python
2.0 : float
# elm
2.0 : Float
BoolFlag()# python
True : bool
# elm
True : Bool
argument: Flag
NullableFlag(StringFlag())# python
None : str | None
# elm
Nothing : Maybe String
# python
"foo" : str | None
# elm
Just "foo" : Maybe String
argument: Flag
ListFlag(StringFlag())# python
["foo"] : list[str]
# elm
["foo"] : List String
argument: dict[str, Flag]
ObjectFlag({"hello": StringFlag()})# python
{"hello": "world"} : dict[str, str]
# elm
{ hello = "world" } : { hello : String }
Elm calls these custom types, but you may also know them as the following:
- Discriminated unions
- Tagged unions
- Sum types
- Algebraic data types
argument: list[tuple[str, Flag]]
CustomTypeFlag(variants=[("A", StringFlag()), ("B", IntFlag())])# python
"hello" : Union[str, int]
2 : Union[str, int]
# elm
A "hello" : Custom
B 2 : Custom