Dependency

The base protocol for all dependency definitions in the napkin architecture.

protocol Dependency : AnyObject, Sendable

Mentioned In

Streaming State Down the Tree
Getting Started

Overview

A Dependency protocol defines the set of dependencies that a napkin requires from its parent. The parent’s Component must conform to this protocol to provide the required dependencies.

Overview

Dependencies flow down the napkin tree:

A child napkin defines a dependency protocol listing what it needs
The parent’s component conforms to that protocol
The parent’s component is passed to the child’s builder
The child’s builder uses the dependency to construct its napkin

Defining Dependencies

Create a protocol that extends Dependency and declares the required services:

protocol MyFeatureDependency: Dependency {
    var userService: UserServiceProtocol { get }
    var analyticsService: AnalyticsServiceProtocol { get }
    var logger: LoggerProtocol { get }
}

Providing Dependencies

The parent component conforms to the child’s dependency protocol:

final class ParentComponent: Component<ParentDependency>, MyFeatureDependency {

    var userService: UserServiceProtocol {
        return dependency.userService  // Pass through from grandparent
    }

    var analyticsService: AnalyticsServiceProtocol {
        return shared { AnalyticsService() }  // Create locally
    }

    var logger: LoggerProtocol {
        return shared { Logger() }
    }
}

See Also
Component

See Also
EmptyDependency

See Also
Builder

Relationships

Conforming Types

Inherited By

EmptyDependency