Namespace: webdriver.promise
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class ControlFlow

final
webdriver.EventEmitter
  └ webdriver.promise.ControlFlow

Handles the execution of scheduled tasks, each of which may be an asynchronous operation. The control flow will ensure tasks are executed in the ordered scheduled, starting each task only once those before it have completed.

Each task scheduled within this flow may return a webdriver.promise.Promise to indicate it is an asynchronous operation. The ControlFlow will wait for such promises to be resolved before marking the task as completed.

Tasks and each callback registered on a webdriver.promise.Promise will be run in their own ControlFlow frame. Any tasks scheduled within a frame will take priority over previously scheduled tasks. Furthermore, if any of the tasks in the frame fail, the remainder of the tasks in that frame will be discarded and the failure will be propagated to the user through the callback/task's promised result.

Each time a ControlFlow empties its task queue, it will fire an IDLE event. Conversely, whenever the flow terminates due to an unhandled error, it will remove all remaining tasks in its queue and fire an UNCAUGHT_EXCEPTION event. If there are no listeners registered with the flow, the error will be rethrown to the global error handler.

new ControlFlow()

Parameters
None.

Instance Methods

addListener(type, listenerFn, opt_scope)code »

Registers a listener.

Defined by: webdriver.EventEmitter

Parameters
typestring

The type of event to listen for.

listenerFnFunction

The function to invoke when the event is fired.

opt_scope?Object=

The object in whose scope to invoke the listener.

Returns
webdriver.EventEmitter

A self reference.

emit(type, var_args)code »

Fires an event and calls all listeners.

Defined by: webdriver.EventEmitter

Parameters
typestring

The type of event to emit.

var_args...*

Any arguments to pass to each listener.

<T> execute(fn, opt_description)code »

Schedules a task for execution. If there is nothing currently in the queue, the task will be executed in the next turn of the event loop. If the task function is a generator, the task will be executed using webdriver.promise.consume.

Parameters
fnfunction(): (T|webdriver.promise.Promise<T>)

The function to call to start the task. If the function returns a webdriver.promise.Promise, this instance will wait for it to be resolved before starting the next task.

opt_descriptionstring=

A description of the task.

Returns
webdriver.promise.Promise<T>

A promise that will be resolved with the result of the action.

getSchedule(opt_includeStackTraces)code »

Generates an annotated string describing the internal state of this control flow, including the currently executing as well as pending tasks. If opt_includeStackTraces === true, the string will include the stack trace from when each task was scheduled.

Parameters
opt_includeStackTracesstring=

Whether to include the stack traces from when each task was scheduled. Defaults to false.

Returns
string

String representation of this flow's internal state.

listeners(type)code »

Returns a mutable list of listeners for a specific type of event.

Defined by: webdriver.EventEmitter

Parameters
typestring

The type of event to retrieve the listeners for.

Returns
Array<{fn: Function, oneshot: boolean, scope: ?(Object)}>

The registered listeners for the given event type.

on(type, listenerFn, opt_scope)code »

An alias for #addListener().

Defined by: webdriver.EventEmitter

Parameters
typestring

The type of event to listen for.

listenerFnFunction

The function to invoke when the event is fired.

opt_scope?Object=

The object in whose scope to invoke the listener.

Returns
webdriver.EventEmitter

A self reference.

once(type, listenerFn, opt_scope)code »

Registers a one-time listener which will be called only the first time an event is emitted, after which it will be removed.

Defined by: webdriver.EventEmitter

Parameters
typestring

The type of event to listen for.

listenerFnFunction

The function to invoke when the event is fired.

opt_scope?Object=

The object in whose scope to invoke the listener.

Returns
webdriver.EventEmitter

A self reference.

removeAllListeners(opt_type)code »

Removes all listeners for a specific type of event. If no event is specified, all listeners across all types will be removed.

Defined by: webdriver.EventEmitter

Parameters
opt_typestring=

The type of event to remove listeners from.

Returns
webdriver.EventEmitter

A self reference.

removeListener(type, listenerFn)code »

Removes a previously registered event listener.

Defined by: webdriver.EventEmitter

Parameters
typestring

The type of event to unregister.

listenerFnFunction

The handler function to remove.

Returns
webdriver.EventEmitter

A self reference.

reset()code »

Resets this instance, clearing its queue and removing all event listeners.

timeout(ms, opt_description)code »

Inserts a setTimeout into the command queue. This is equivalent to a thread sleep in a synchronous programming language.

Parameters
msnumber

The timeout delay, in milliseconds.

opt_descriptionstring=

A description to accompany the timeout.

Returns
webdriver.promise.Promise

A promise that will be resolved with the result of the action.

toString()code »

Returns a string representation of this control flow, which is its current schedule, sans task stack traces.

Returns
string

The string representation of this contorl flow.

<T> wait(condition, opt_timeout, opt_message)code »

Schedules a task that shall wait for a condition to hold. Each condition function may return any value, but it will always be evaluated as a boolean.

Condition functions may schedule sub-tasks with this instance, however, their execution time will be factored into whether a wait has timed out.

In the event a condition returns a Promise, the polling loop will wait for it to be resolved before evaluating whether the condition has been satisfied. The resolution time for a promise is factored into whether a wait has timed out.

If the condition function throws, or returns a rejected promise, the wait task will fail.

If the condition is defined as a promise, the flow will wait for it to settle. If the timeout expires before the promise settles, the promise returned by this function will be rejected.

If this function is invoked with timeout === 0, or the timeout is omitted, the flow will wait indefinitely for the condition to be satisfied.

Parameters
condition(webdriver.promise.Promise<T>|function(): ?)

The condition to poll, or a promise to wait on.

opt_timeoutnumber=

How long to wait, in milliseconds, for the condition to hold before timing out. If omitted, the flow will wait indefinitely.

opt_messagestring=

An optional error message to include if the wait times out; defaults to the empty string.

Returns
webdriver.promise.Promise<T>

A promise that will be fulfilled when the condition has been satisified. The promise shall be rejected if the wait times out waiting for the condition.

Throws
TypeError

If condition is not a function or promise or if timeout is not a number >= 0.

Types

ControlFlow.EventType

Events that may be emitted by an webdriver.promise.ControlFlow.