Conditions

You can use a switch block as a selection mechanism that allows the value of an expression to control the flow of a workflow's execution. If a value matches, that condition's statement is executed.

If no matching expression is found, the workflow looks for an optional default condition: - condition: true. This should be the last condition in the switch block as they are evaluated in order and the first match found is executed. If there is neither a match nor a default condition, the workflow continues execution with the step that immediately follows.

Each switch block can include a maximum of 50 conditions. Each expression must evaluate to true or false. (Learn how to define and use expressions.)

For example, you can control the order of a workflow's execution by using a switch block to jump between steps based on a conditional expression:

YAML

  - STEP_NAME_A:
      switch:
          - condition: ${EXPRESSION_A}
            next: STEP_NAME_B
          - condition: ${EXPRESSION_B}
            next: STEP_NAME_C
          - condition: true
            next: STEP_NAME_C
      next: STEP_NAME_D

JSON

  [
    {
      "STEP_NAME_A": {
        "switch": [
          {
            "condition": "${EXPRESSION_A}",
            "next": "STEP_NAME_B"
          },
          {
            "condition": "${EXPRESSION_B}",
            "next": "STEP_NAME_C"
          }
          {
            "condition": true,
            "next": "STEP_NAME_C"
          }
        ],
        "next": "STEP_NAME_D"
      }
    }
  ]

You can also nest multiple steps inside a switch block:

YAML

  - STEP_NAME_A:
      switch:
          - condition: ${EXPRESSION}
            steps:
                - STEP_NAME_B:
                    ...
                - STEP_NAME_C:
                    ...
      next: STEP_NAME_D

JSON

  [
    {
      "STEP_NAME_A": {
        "switch": [
          {
            "condition": "${EXPRESSION}",
            "steps": [
              {
                "STEP_NAME_B": {
                  ...
                }
              },
              {
                "STEP_NAME_C": {
                  ...
                }
              }
            ]
          }
        ],
        "next": "STEP_NAME_D"
      }
    }
  ]

Note that the steps block is optional. It can contain the following:

For more information about defining a workflow's order of execution, see Jumps and Control the order of execution in a workflow.

Samples

These samples demonstrate the syntax.

Conditional jumps to specific steps

You might want a workflow to jump to a specific step when a condition is met. These two samples execute steps depending on the value returned by the first step of the workflow.

YAML

- first_step:
    call: http.get
    args:
      url: https://www.example.com/callA
    result: first_result
- where_to_jump:
    switch:
      - condition: ${first_result.body.SomeField < 10}
        next: small
      - condition: ${first_result.body.SomeField < 100}
        next: medium
    next: large
- small:
    call: http.get
    args:
      url: https://www.example.com/SmallFunc
    next: end
- medium:
    call: http.get
    args:
      url: https://www.example.com/MediumFunc
    next: end
- large:
    call: http.get
    args:
      url: https://www.example.com/LargeFunc
    next: end

JSON

[
  {
    "first_step": {
      "call": "http.get",
      "args": {
        "url": "https://www.example.com/callA"
      },
      "result": "first_result"
    }
  },
  {
    "where_to_jump": {
      "switch": [
        {
          "condition": "${first_result.body.SomeField < 10}",
          "next": "small"
        },
        {
          "condition": "${first_result.body.SomeField < 100}",
          "next": "medium"
        }
      ],
      "next": "large"
    }
  },
  {
    "small": {
      "call": "http.get",
      "args": {
        "url": "https://www.example.com/SmallFunc"
      },
      "next": "end"
    }
  },
  {
    "medium": {
      "call": "http.get",
      "args": {
        "url": "https://www.example.com/MediumFunc"
      },
      "next": "end"
    }
  },
  {
    "large": {
      "call": "http.get",
      "args": {
        "url": "https://www.example.com/LargeFunc"
      },
      "next": "end"
    }
  }
]

YAML

- getCurrentTime:
    call: http.get
    args:
      url: https://timeapi.io/api/Time/current/zone?timeZone=Europe/Amsterdam
    result: currentTime
- conditionalSwitch:
    switch:
      - condition: ${currentTime.body.dayOfWeek == "Friday"}
        next: friday
      - condition: ${currentTime.body.dayOfWeek == "Saturday" or currentTime.body.dayOfWeek == "Sunday"}
        next: weekend
    next: workWeek
- friday:
    return: "It's Friday! Almost the weekend!"
- weekend:
    return: "It's the weekend!"
- workWeek:
    return: "It's the work week."

JSON

[
  {
    "getCurrentTime": {
      "call": "http.get",
      "args": {
        "url": "https://timeapi.io/api/Time/current/zone?timeZone=Europe/Amsterdam"
      },
      "result": "currentTime"
    }
  },
  {
    "conditionalSwitch": {
      "switch": [
        {
          "condition": "${currentTime.body.dayOfWeek == \"Friday\"}",
          "next": "friday"
        },
        {
          "condition": "${currentTime.body.dayOfWeek == \"Saturday\" or currentTime.body.dayOfWeek == \"Sunday\"}",
          "next": "weekend"
        }
      ],
      "next": "workWeek"
    }
  },
  {
    "friday": {
      "return": "It's Friday! Almost the weekend!"
    }
  },
  {
    "weekend": {
      "return": "It's the weekend!"
    }
  },
  {
    "workWeek": {
      "return": "It's the work week."
    }
  }
]

Switch structure with embedded steps

A switch structure can also be used to support direct execution of steps when a condition is met, without jumping to other steps. This improves the readability of a workflow by reducing the number of steps in the workflow definition.

YAML

- step1:
    assign:
      - a: 1
- step2:
    switch:
      - condition: ${a==1}
        steps:
          - stepA:
              assign:
                - a: ${a+7}
          - stepB:
              return: ${"increase a to:"+string(a)}
- step3:
    return: ${"default a="+string(a)}

JSON

[
  {
    "step1": {
      "assign": [
        {
          "a": 1
        }
      ]
    }
  },
  {
    "step2": {
      "switch": [
        {
          "condition": "${a==1}",
          "steps": [
            {
              "stepA": {
                "assign": [
                  {
                    "a": "${a+7}"
                  }
                ]
              }
            },
            {
              "stepB": {
                "return": "${\"increase a to:\"+string(a)}"
              }
            }
          ]
        }
      ]
    }
  },
  {
    "step3": {
      "return": "${\"default a=\"+string(a)}"
    }
  }
]