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PROTOCOL

Workflow

public protocol Workflow<Rendering, Output>: AnyWorkflowConvertible

Defines a node in the workflow tree.

Initialization and Updating

A workflow node comes into existence after its parent produces an instance of that workflow and uses it during a render pass (see the render method for more details).

  • If this is the first time the parent has rendered a child of this type, a new workflow node is created. The workflow passed in from the parent will be used to invoke initialState() to obtain an initial state.

  • If the parent had previously rendered a child of this type, the existing workflow node will be updated. workflowDidChange(from:state:) will be invoked to allow the workflow to respond to the change.

Render

After a workflow node has been created, or any time its state changes, a render pass occurs. The render pass takes the workflow that was passed down from the parent along with the current state and generates a value of type Rendering. In a common case, a workflow might render to a screen model for display.

func render(state: State, context: RenderContext<Self>) -> MyScreenModel {
    return MyScreenModel()
}

Methods

makeInitialState()

func makeInitialState() -> State

This method is invoked once when a workflow node comes into existence.

  • Returns: The initial state for the workflow.

workflowDidChange(from:state:)

func workflowDidChange(from previousWorkflow: Self, state: inout State)

Called when a new workflow is passed down from the parent to an existing workflow node.

  • Parameter previousWorkflow: The workflow before the update.
  • Parameter state: The current state.

Parameters

Name Description
previousWorkflow The workflow before the update.
state The current state.

render(state:context:)

func render(state: State, context: RenderContext<Self>) -> Rendering

Called by the internal Workflow infrastructure to “render” the current state into Rendering. A workflow’s Rendering type is commonly a view or screen model.

  • Parameter state: The current state.
  • Parameter context: The workflow context is the composition point for the workflow tree. To use a nested workflow, instantiate it based on the current state, then call rendered(in:key:outputMap:). This will return the child’s Rendering type after creating or updating the nested workflow.

Parameters

Name Description
state The current state.
context The workflow context is the composition point for the workflow tree. To use a nested workflow, instantiate it based on the current state, then call rendered(in:key:outputMap:). This will return the child’s Rendering type after creating or updating the nested workflow.