Decision Branching

[danielgerlag]

Decision Branching

You can define multiple independent branches within your workflow and select one based on an expression value.

For the fluent API, we define our branches with the CreateBranch() method on the workflow builder. We can then select a branch using the Decision step.

This workflow will select branch1 if the value of data.Value1 is one, and branch2 if it is two.

var branch1 = builder.CreateBranch()
    .StartWith<PrintMessage>()
        .Input(step => step.Message, data => "hi from 1")
    .Then<PrintMessage>()
        .Input(step => step.Message, data => "bye from 1");

var branch2 = builder.CreateBranch()
    .StartWith<PrintMessage>()
        .Input(step => step.Message, data => "hi from 2")
    .Then<PrintMessage>()
        .Input(step => step.Message, data => "bye from 2");


builder
    .StartWith<HelloWorld>()
    .Decide(data => data.Value1)
        .Branch("one", branch1)
        .Branch("two", branch2);

The JSON representation would look somthing like this.

{
  "Id": "DecisionWorkflow",
  "Version": 1,
  "DataType": "MyApp.MyData, MyApp",
  "Steps": [
    {
      "Id": "decide",
      "StepType": "WorkflowCore.Primitives.Decide, WorkflowCore",
      "Inputs": 
      {
        "Expression": "data.Value1" 
      },
      "OutcomeSteps":
      {
        "Print1": "\"one\"",
        "Print2": "\"two\""
      }
    },
    {
      "Id": "Print1",
      "StepType": "MyApp.PrintMessage, MyApp",
      "Inputs": 
	  { 
		"Message": "\"Hello from 1\"" 
	  }
    },
    {
      "Id": "Print2",
      "StepType": "MyApp.PrintMessage, MyApp",
      "Inputs": 
	  { 
	    "Message": "\"Hello from 2\"" 
	  }
    }
  ]
}

Outcomes for JSON workflows

You can now specify OutcomeSteps for a step in JSON and YAML workflow definitions.

"OutcomeSteps":
{
	"<<Step1 Id>>": "<<expression>>",
	"<<Step2 Id>>": "<<expression>>"
}

If the outcome of a step matches a particular expression, that step would be scheduled as the next step to execute.