brainhops._core.enum

The converter of a free-text value that has a list of known terms.

The known terms are the members of an enum. A string that is the value of a member becomes that member, any other string stays a string, and None stays None. A field annotated with ConvertTo(EnumConverter(SpaceEnum)) therefore holds a SpaceEnum member for a known space and the plain string for any other space.

bagof does not convert a Union[Enum, str] this way by itself. Its union converter returns a value that already fits one branch of the union as it is, so a string stays a string, and the enum branch is never tried. Registering a converter for the union does not help either, because bagof matches a parametrised union by equality: each enum, and each wrapping of its union (Optional[...], or the metadata Maybe[...], which flatten into other unions), would need a registration of its own, and a shape that was left out would silently keep the string. An explicit converter on the field cannot be missed.

The converter is a class rather than a closure so that it has a readable repr and can be pickled, since it is stored in the metadata of a field.

Examples:

>>> from brainhops.datamodel.enums import SpaceEnum
>>> convert = EnumConverter(SpaceEnum)
>>> convert("scanner")
<SpaceEnum.scanner: 'scanner'>
>>> convert("my-template")
'my-template'
>>> convert
EnumConverter(SpaceEnum)

Parameters:

__call__(value: Any) -> Any