When you specify the fields attribute on a :class:`~django_easyfilters.FilterSet` subclass, various different Filter classes will be chosen depending on the type of field. They are listed below, with the keyword argument options that they take.
This is the base class for all filters, and has provides some options:
The parameter in the query string that will be used for this field. This can be useful for shortening the query strings that are generated.
If True, this will cause the choices to be sorted so that the choices with the largest 'count' appear first.
This is used for ForeignKey fields
This is used for ManyToMany fields
This is used for fields that have 'choices' defined. The choices presented will be in the order specified in 'choices'.
This is the most complex of the filters, as it allows drill-down from year to month to day. It takes the following options:
The maximum number of links to display. If the number of choices at any level does not fit into this value, ranges will be used to shrink the number of choices.
If 'year' or 'month' is specified, the drill-down will be limited to that level.
This filter produces ranges of values for a numeric field. It is the default filter for decimal fields, but can also be used with integer fields. It attempts to make the ranges 'look nice' using rounded numbers in an automatic way. It uses 'drill-down' like DateTimeFilter.
It takes the following options:
The maximum number of links to display. If there fewer distinct values than this in the data, single values will be shown, otherwise ranges.
If this is specified, it will override the (initial) automatic range. The value should be a list of ranges, where each item in the list is either:
- a two-tuple containing the beginning and end range values
- a three-tuple containing the beginning and end range values and a custom label.
If False, only one level of choices will be displayed.
The 'end points' of ranges are handled in the following way: the lower bound is exclusive, and the upper bound is inclusive, apart from for the first range, where both are inclusive. This is designed for a fairly intuitive behaviour.
This is the fallback that is used when nothing else matches.
Custom Filter classes
As described in the :class:`~django_easyfilters.FilterSet` documentation, you can provide your own Filter class for a field. If you do so, it is expected to have the following API:
__init__(field, model, params, **kwargs)
Constructor. field is the string identifying the field, model is the model class, params is a QueryDict (i.e. request.GET). kwargs contains any custom options specified for the filter.
This method takes the QuerySet qs and returns a QuerySet that has filters applied to it, where the filter parameters are defined in the params that were passed to the constructor. The method must be able to extract the relevant parameter, if it exists, and filter the QuerySet accordingly.
This method is passed a fully filtered QuerySet, and must return a list of choices to present to the user. The choices should be instances of django_easyfilters.filters.FilterChoice, which has the attributes:
- label: User presentable text string for the choice
- link_type: choice of FILTER_ADD, FILTER_REMOVE, FILTER_DISPLAY
- count: the number of items for this choice (only for FILTER_ADD)
- params: parameters used to create a link for this option, as a QueryDict
At the moment, all other methods of Filter and subclasses are considered private implementation details. You can subclass Filter if you want, and use its functionality, but it may change without warning.