Action Promise

Nikita's actions always return JavaScript Promise and provide the guarantee that all actions are executed sequentially according to their declaration.

Accessing the action output

The action output is returned after its Promise is fulfilled.

The most elegant and relevant approach to access the action output is using the async/await operators. It avoids a "callback hell" in case you need to pass a result of one action to a configuration property of another action as in the following example:

// Dependency
const assert = require('assert');
// Call anonymous asynchronous function 
(async () => {
  // Define empty array
  history = []
  // New Nikita session
  await nikita
  .call(async function() {
    // Access the action output
    const result = await this.call(() => 'first')
    // Pass result to the next action
    await this.call({
      item: result
    }, function({config}) {
      // Push the first item to the array
      history.push(config.item)
    })
  })
  // Push the second item synchronously after Nikita actions
  history.push('second')
  // Assert the order
  assert.deepEqual(history, ['first', 'second'])
})()

Alternatively, this example can be rewritten using the Promise API methods. To access the result, you can use the then method and pass a callback function. You also can call the finally method and pass a callback function with JavaScript commands to run them synchronously after the Nikita actions:

// Dependency
const assert = require('assert');
// Define empty array
history = []
// New Nikita session
nikita
.call(function() {
  // Call an action
  this.call(() => 'first')
  // Access the action output
  .then((result) => {
    // Pass result to the next action
    this.call({
      item: result
    }, ({config}) => {
      // Push the first item to the array
      history.push(config.item)
    })
  })
})
.finally(() => {
  // Push the second item synchronously after Nikita actions
  history.push('second')
  // Assert the order
  assert.deepEqual(history, ['first', 'second'])
})

When an error occurs while executing actions, it can be caught. Read the following documentation about handling errors in Nikita.

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