MemoryPersistence<T>

Implements: IConfigurable, IReferenceable, IOpenable, ICleanable

Description

The MemoryPersistence class allows you to create persistence components that store data in memory.

Important points

• This is the most basic persistence component that is only able to store data items of any type.
• Specific CRUD operations over the data items must be implemented in child classes by accessing the this._items property and calling the save method.
• The component supports loading and saving items from another data source. This allows to use it as a base class for file and other types of persistence components that cache all data in memory.

Configuration parameters

options:

• max_page_size: maximum number of items returned in a single page (default: 100)

References

• *:logger:*:*:1.0 - (optional) (../../../components/log/ilogger) components to pass log messages

Constructors

Creates a new instance of the memory persistence component.

MemoryPersistence([ILoader loader, ISaver saver])

• loader: ILoader - (optional) loader used to load items from an external datasource.
• saver: ISaver - (optional) saver used to save items to an external datasource.

Fields

Instance methods

clear

Clears the component’s state.

Future clear(String? correlationId)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.

create

Creates a data item.

Future<T?> create(String? correlationId, T item)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.
• item: T - item to be created.
• returns: Future<T> - created item

deleteByFilter

Deletes data items that match to a given filter. This method shall be called by a public deleteByFilter method from a child class that receives FilterParams and converts them into a filter function.

Future deleteByFilterEx(String? correlationId, filter)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.
• filter: dynamic - (optional) filter function used to filter items.

getCountByFilter

Gets the number of items retrieved by a given filter.

This method shall be called by a public getCountByFilter method from a child class that receives FilterParams and converts them into a filter function.

Future<int> getCountByFilterEx(String? correlationId, filter)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.
• filter: dynamic - id of the item to be deleted
• returns: Future<int> - number of data items that satisfy the filter.

getListByFilterEx

Gets a list of data items retrieved by a given filter and sorted according to sorting parameters.

This method shall be called by a public getListByFilterEx method from a child class that receives FilterParams and converts them into a filter function.

Future<List<T>> getListByFilterEx(String? correlationId, filter, sort, select)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.
• filter: dynamic - (optional) filter function used to filter items
• sort: dynamic - (optional) sorting parameters
• select: dynamic - (optional) projection parameters (not used yet)
• returns: Future<List<T>> - data list of filtered results.

getOneRandom

Gets a random item from items that match to a given filter.

This method shall be called by a public getOneRandom method from a child class that receives FilterParams and converts them into a filter function.

Future<T> getOneRandom(String? correlationId, filter)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.
• filter: dynamic - (optional) a filter function to filter items.
• returns: Future<T> - random item.

getPageByFilter

Gets a page of data items retrieved by a given filter and sorted according to sorting parameters.

This method shall be called by a public getPageByFilter method from a child class that receives FilterParams and converts them into a filter function.

Future<DataPage> getPageByFilterEx(String? correlationId, Function filter, PagingParams paging, Function sort)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.
• filter: Function - filter function used to filter items
• paging: PagingParams - (optional) paging parameters
• sort: Function - (optional) sorting parameters
• returns: Future<DataPage> - data page with filtered results.

isOpen

Checks if the component is open.

@override

bool isOpen()

• returns: bool - true if the component is open and false otherwise.

load

Loads items.

Future _load(String? correlationId)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.

open

Opens the component.

@override

Future open(String? correlationId)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.

save

Saves items to an external data source using a configured saver component.

Future save(String? correlationId)

• correlationId: String? - (optional) transaction id used to trace execution through the call chain.

setReferences

Sets the component’s references. References must match configured dependencies.

@override

void setReferences(IReferences references)

• references: IReferences - references to set.

Examples

class MyMemoryPersistence extends MemoryPersistence<MyData> {
   Future<MyData> getByName(String? correlationId, String name) async {
        var item = items.firstWhere((d) => d.name == name);
       return item;
    });
    Future<MyData> set(String correlatonId, MyData item) async {
        items = items.where((d) => d.name != name);
        items.add(item);
        await save(correlationId);
        return item;
    }
}

var persistence = MyMemoryPersistence();
persistence.set("123", { name: "ABC" })
var item = await persistence.getByName("123", "ABC")
print(item);                   // Result: { name: "ABC" }

See also

• MemoryPersistence