Property References

To filter on a property you need a property reference. For example, to find all people named Smith you need a reference to the firstName property. Other databases might call this a column. Any DataModel can supply these references.

These operations can be defined in Kotlin or any of the serialization formats Maryk supports.

Example models

This Person model has two top level fields (firstName, lastName) and an embedded Address:

object Person : RootDataModel<Person>() {
    val firstName by string(index = 1u)
    val lastName by string(index = 2u)
    val livingAddress by embed(
        index = 3u,
        dataModel = { Address }
    )
}

object Address : DataModel<Address>() {
  val street by string(index = 1u)
  val city by string(index = 2u)
}

Creating property references

With compiled models Kotlin produces type strict property definitions. This means your IDE will help to validate and autocomplete them.

Examples:

// Reference to firstName property
Person { firstName::ref }

// Reference to street through a Person
Person { livingAddress { street::ref } }

For deeper nesting, chain {} blocks and call ::ref on the last property

Model { property { property { property { property { property::ref } } } } }

Creating property references with String notation

When defined in YAML or JSON, property references can use a simple string format without including the model name.

To refer to the firstName on Person you use firstName and for the street on Address within Person you use livingAddress.street

Referring to values of maps

It is also possible to refer to a value inside a map to filter or order:

// Model contains map with Time as a key
// Refer to the value at 12:23
Model { map refAt Time(12, 23) }

In string notation this becomes map.@12:23. Validation errors that refer to the key use map.$12:23.

Wildcards for maps

Maps support wildcard references for both values and keys:

// Any key in the map
Model { map.refToAnyKey() }

// Any value in the map
Model { map.refToAnyValue() }

String notation:

• map.~ = any map key
• map.* = any map value

Referring to specific values in sets

Items in sets can be selected by value

// Model with a set property of Time
// Refer to the value at Time(12, 23)
Model { set refAt Time(12, 23) }

In string notation this is set.$12:23.

Wildcards for sets

Sets support wildcard references to match any item value:

Model { set.refToAny() }

String notation:

• set.* = any set value

Referring to index of lists

Items in lists can also be selected by index

// Model with list property
// Refer to the value at index 5
Model { list refAt 5 }

In string notation this is list.@5.

list.@<index> and list.* references are usable for filtering and changes. They are not valid for RootDataModel index definitions.