pip_services3_commons.refer.IReferences module

pip_services3_commons.refer.IReferences

Interface for references components.

copyright: Conceptual Vision Consulting LLC 2018-2019, see AUTHORS for more details.
license: MIT, see LICENSE for more details.

class pip_services3_commons.refer.IReferences.IReferences

Bases: abc.ABC

Interface for a map that holds component references and passes them to components to establish dependencies with each obj.

Together with IReferenceable and IUnreferenceable interfaces it implements a Locator pattern that is used by PipServices toolkit for Inversion of Control to assign external dependencies to components.

The IReferences object is a simple map, where keys are locators and values are component references. It allows to add, remove and find components by their locators. Locators can be any values like integers, strings or component types. But most often PipServices toolkit uses Descriptor as locators that match by 5 fields: group, type, kind, name and version.

Example:

class MyController(IReferences):
    _persistence = None

    def set_references(self, references):
        self._persistence = references.get_one_required(Descriptor("mygroup", "persistence", "*", "*", "1.0"))

persistence = MyMongoDbPersistence()

references = References.from_tuples(
Descriptor("mygroup", "persistence", "mongodb", "default", "1.0"), persistence,
Descriptor("mygroup", "controller", "default", "default", "1.0"), controller)

controller.set_references(references)

find(locator: Any, required: bool) → List[Any]

Gets all component references that match specified locator.

Parameters

locator – the locator to find a reference by.
required – forces to raise an error if no reference is found.

Returns

a list with matching component references.

Raises

a ReferenceException when __required is set to true but no references found.

get_all() → List[Any]

Gets all component references registered in this reference map.

Returns: a list with component references.

get_all_locators() → List[Any]

Gets locators for all registered component references in this reference map.

Returns: a list with component locators.

get_one_before(reference, locator)

get_one_optional(locator: Any) → Any

Gets an optional component reference that matches specified locator.

Parameters: locator – the locator to find references by.
Returns: a matching component reference or null if nothing was found.

get_one_required(locator: Any) → Any

Gets a __required component reference that matches specified locator.

Parameters: locator – the locator to find a reference by.
Returns: a matching component reference.
Raises: a ReferenceException when no references found.

get_optional(locator: Any) → List[Any]

Gets all component references that match specified locator.

Parameters: locator – the locator to find references by.
Returns: a list with matching component references or empty list if nothing was found.

get_required(locator: Any) → List[Any]

Gets all component references that match specified locator. At least one component reference must be present. If it doesn’t the method throws an error.

Parameters: locator – the locator to find references by.
Returns: a list with matching component references.
Raises: a ReferenceException when no references found.

put(locator: Any = None, reference: Any = None)

Puts a new reference into this reference map.

Parameters

locator – a component reference to be added.
reference – a locator to find the reference by.

remove(locator: Any) → Any

Removes a previously added reference that matches specified locator. If many references match the locator, it removes only the first one. When all references shall be removed, use :func:remove_all method instead.

Parameters: locator – a locator to remove reference
Returns: the removed component reference.

remove_all(locator: Any) → List[Any]

Removes all component references that match the specified locator.

Parameters: locator – a locator to remove reference
Returns: a list, containing all removed references.