DependencyResolver

Implements: IReferenceable, IReconfigurable

Description

The DependencyResolver is a helper class that allows you to resolve component dependencies. It is configured to resolve named dependencies by a specific locator.

Important points

• During deployment the dependency locator can be changed. This mechanism can be used to clarify a specific dependency among several alternatives. Typically components are configured to retrieve the first dependency that matches a logical group, type and version. However, if the container contains more than one instance and the resolution has to be specific about those instances, they can be given a unique name and the dependency resolvers can be reconfigured to retrieve dependencies according to their name.

Configuration parameters

• dependencies:
  • [dependency name 1]: Dependency 1 locator (descriptor)
  • …
  • [dependency name N]: Dependency N locator (descriptor)

References

References must match configured dependencies.

Constructors

Creates a new instance of the dependency resolver.

See ConfigParams, IReferences

DependencyResolver([ConfigParams? config, IReferences? references])

• config: ConfigParams - (optional) default configuration where key the is dependency name and value is the locator (descriptor)
• references: IReferences - (optional) default component references

Instance methods

configure

Configures the component with specified parameters.

@override

void configure(ConfigParams config)

• config: ConfigParams - configuration parameters to set.

find

Finds all matching dependencies by their name.

List<T> find<T>(String name, bool required)

• name: String - dependency name to locate.
• required: bool - true to raise an exception when no dependencies are found.
• returns: List<T> - list of found dependencies

getOneOptional

Gets one optional dependency by its name.

T? getOneOptional<T>(String name)

• name: String - dependency name to locate.
• returns: T? - dependency reference or null if the dependency was not found.

GetOneRequired

Gets one required dependency by its name. At least one dependency must present. If the dependency was found it throws a ReferenceException.

T getOneRequired<T>(String name)

• name: String - dependency name to locate.
• returns: T - dependency reference

getOptional

Gets all optional dependencies by their name.

List<T> getOptional<T>(String name)

• name: String - dependency name to locate.
• returns: List<T> - list with found dependencies or empty list if no dependency was found.

getRequired

Gets all required dependencies by their name. At least one dependency must be present. If no dependency was found, it throws a ReferenceException

List<T> getRequired<T>(String name)

• name: String - dependency name to locate.
• returns: List<T> - list with found dependencies.

put

Adds a new dependency into this resolver.

void put(String name, locator)

• name: String - dependency’s name.
• locator: dynamic - locator to find the dependency by.

setReferences

Sets the component references. References must match configured dependencies.

void setReferences(IReferences references)

• references: IReferences - references to set.

Static methods

fromTuples

Creates a new DependencyResolver from a list of key-value pairs called tuples where key is a dependency name and value the depedency locator (descriptor).

static DependencyResolver fromTuples(List tuples)

• tuples: List - list of values where odd elements are dependency names and the following even elements are dependency locators (descriptor).
• returns: DependencyResolver - newly created DependencyResolver.

Examples

class MyComponent implements IConfigurable, IReferenceable {
    DependencyResolver _dependencyResolver  = new DependencyResolver();
    IMyPersistence _persistence ;
    ...
     MyComponent() {
        _dependencyResolver.put('persistence', new Descriptor('mygroup', 'persistence', '*', '*', '1.0'));
    }

    configure(ConfigParams config ) {
        _dependencyResolver.configure(config);
    }

    setReferences(IReferences references) {
        _dependencyResolver.setReferences(references);
        _persistence = _dependencyResolver.getOneRequired<IMyPersistence>('persistence');
    }
}
// Create mycomponent and set specific dependency out of many
var component =  MyComponent();
component.configure(ConfigParams.fromTuples([
    'dependencies.persistence', 'mygroup:persistence:*:persistence2:1.0'
// Override default persistence dependency
]));

component.setReferences(References.fromTuples([
     Descriptor('mygroup','persistence','*','persistence1','1.0'),  MyPersistence(),
     Descriptor('mygroup','persistence','*','persistence2','1.0'),  MyPersistence()
// This dependency shall be set
]));

See also

• IReferences