Parallel Command

Run a series of commands in parallel. The Parallel command starts running all child commands simultaneously. The Parallel command finishes when all the defined child commands have finished. When the Parallel command stops, all running commands stop.

Properties

The Parallel command has the properties shown in the following table, in addition to the common command properties. Set the type property to Parallel.

In the following table, the "Default" column shows "Required" for properties that must have a value for the command to run. Otherwise it displays the default value, which might be none.

Property Type Default Description

commands

Array of commands

Required

An unordered list of command to run in parallel.

data

Array

[]

A list of data to map against the commands.

In fast mode, the parallel command runs all of the sub-commands in parallel, but without delays (giving a net zero duration).

commands

An un-ordered array of commands to run in parallel. Once all commands have finished running, the Parallel command finishes. The delay value set for the Parallel command is added to the delay value set for each of the commands in the array. In the following example, the first SendEvent command starts after 1500 milliseconds, and the second SendEvent command after 750 milliseconds, which means the second SendEvent command starts before the first.

{
  "type": "Parallel",
  "delay": 500,
  "commands": [
    {
      "type": "SendEvent",
      "delay": 1000
    },
    {
      "type": "SendEvent",
      "delay": 250
    }
  ]
}

data

The array of data to iterate over. When the data array contains data, the Parallel command iterates over that array and creates a new Sequential command for each value in the array. Each new Sequential command contains the commands from the original commands property. This is similar to the way data array inflation works for multiple-child components. The resulting Parallel command then runs all these Sequential commands at the same time.

For example, the following Parallel command contains two commands in commands and two strings in the data array.

{
  "type": "Parallel",
  "data": ["item1", "item2"],
  "commands": [ 
    {
      "type": "CustomCommand1",
      "item": "${data}"
    }, 
    {
      "type": "CustomCommand2",
      "item": "${data}"
    }
  ]
}

This command expands into a Parallel command that contains one Sequential for each of the two items in data. The final command to run is therefore the following.

{
  "type": "Parallel",
  "commands": [
    {
      "type": "Sequential",
      "commands": [
        {
          "type": "CustomCommand1",
          "item": "item1"
        }, 
        {
          "type": "CustomCommand2",
          "item": "item1"
        }
      ]
    },
    {
      "type": "Sequential",
      "commands": [
        {
          "type": "CustomCommand1",
          "item": "item2"
        }, 
        {
          "type": "CustomCommand2",
          "item": "item2"
        }
      ]
    }
  ]
}

During iteration, the data-binding context extends to include the properties shown in the following table.

Name Description

data

Data assigned from the data array property.

index

The 0-based index of the current data item.

length

The total number of data items in the data array.

These properties are set when the data array property contains at least one item.

Parallel example with the data array

The following example displays a list of items. The button defines a Parallel with three SetValue commands to select a random color from a list, change the color of an item to the random color, and then change the text of the item to the name of the color. The Parallel sets the data array to the same list of items displayed in the Sequence.

When the command runs, each item in the list first changes color, then changes its text. The items in the list all update at the same time.

For a similar example in which the list items update one after another, see Sequential example with the data array.

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