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PROTOCOL

Workflow

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()

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

  • Returns: The initial state for the workflow.

workflowDidChange(from: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.

render(state:context:)

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.