DataFilter

This is an abstract and sealed component for defining data querying logic separate from an application's database semantics. The rationale for this is discussed here.

The component has two subclasses DataFilter.Field and DataFilter.Compound, which represent definitions for direct field filtering criteria and compound (OR/AND) queries, respectively.

DataFilter.Field

Defines a data querying criteria in the form of <fieldName> <operation> [optional <value>]. This is typically used to define equals, greater than, less than, contains, etc.

data class Field<Value : Any>(
    val field: String,
    val operation: Operation,
    val value: Value
) : DataFilter()

A set of utilities and extension functions can be used to construct field filters for various types of field matching criteria.

// Filter records where "size" is greater than 20
val filter = "size".gt(20)

// Filter records where "status" is not equal to Status.PUBLISHED
Document::status.ne(Status.PUBLISHED)

DataFilter.Compound

Combines a set of DataFilter objects with a logical AND or OR criteria.

data class Compound(
    val operator: Operator,
    val subFilters: Collection<DataFilter>
) : DataFilter()

Below is an example of a compound filter using a set of built-in utilities. Although, in an Invirt application, when these objects are being read from query parameters, you wouldn't normally have to construct these objects manually.

val filter = orFilter(
    Document::status.ne(Status.PUBLISHED),
    andFilter(
        Document::status.eq(Status.PUBLISHED),
        Document::size.gte(200000)
    )
)