81 lines
3.1 KiB
Markdown
81 lines
3.1 KiB
Markdown
## Task lifecycle
|
|
|
|
We handle several kinds of tasks in zone.js,
|
|
|
|
- MacroTask
|
|
- MicroTask
|
|
- EventTask
|
|
|
|
For details, please refer to [here](../dist/zone.js.d.ts)
|
|
|
|
This document will explain the lifecycle (state-transition) of different types of tasks and also the triggering of various zonespec's callback during that cycle.
|
|
|
|
The motivation to write this document has come from this [PR](https://github.com/angular/zone.js/pull/629) of @mhevery. This has made the task's state more clear. Also, tasks can now be cancelled and rescheduled in different zone.
|
|
|
|
### MicroTask
|
|
Such as Promise.then, process.nextTick, they are microTasks, the lifecycle(state transition)
|
|
looks like this.
|
|
|
|
|
|
|
|
ZoneSpec's onHasTask callback will be triggered when the first microTask were scheduled or the
|
|
last microTask was invoked.
|
|
|
|
### EventTask
|
|
Such as EventTarget's EventListener, EventEmitter's EventListener, their lifecycle(state transition)
|
|
looks like this.
|
|
|
|
|
|
|
|
ZoneSpec's onHasTask callback will be triggered when the first eventTask were scheduled or the
|
|
last eventTask was cancelled.
|
|
|
|
EventTask will go back to scheduled state after invoked(running state), and will become notScheduled after cancelTask(such as removeEventListener)
|
|
|
|
### MacroTask
|
|
|
|
#### Non Periodical MacroTask
|
|
Such as setTimeout/XMLHttpRequest, their lifecycle(state transition)
|
|
looks like this.
|
|
|
|
|
|
|
|
ZoneSpec's onHasTask callback will be triggered when the first macroTask were scheduled or the
|
|
last macroTask was invoked or cancelled.
|
|
|
|
Non periodical macroTask will become notScheduled after being invoked or being cancelled(such as clearTimeout)
|
|
|
|
#### Periodical MacroTask
|
|
Such as setInterval, their lifecycle(state transition)
|
|
looks like this.
|
|
|
|
|
|
|
|
ZoneSpec's onHasTask callback will be triggered when first macroTask was scheduled or last macroTask
|
|
was cancelled, it will not triggered after invoke, because it is periodical and become scheduled again.
|
|
|
|
Periodical macroTask will go back to scheduled state after invoked(running state), and will become notScheduled after cancelTask(such as clearInterval)
|
|
|
|
### Reschedule Task to a new zone
|
|
Sometimes you may want to reschedule task into different zone, the lifecycle looks like
|
|
|
|
|
|
|
|
the ZoneTask's cancelScheduleRequest method can be only called in onScheduleTask callback of ZoneSpec,
|
|
because it is still under scheduling state.
|
|
|
|
And after rescheduling, the task will be scheduled to new zone(the otherZoneSpec in the graph),
|
|
and will have nothing todo with the original zone.
|
|
|
|
### Override zone when scheduling
|
|
Sometimes you may want to just override the zone when scheduling, the lifecycle looks like
|
|
|
|
|
|
|
|
After overriding, the task will be invoked/cancelled in the new zone(the otherZoneSpec in the graph),
|
|
but hasTask callback will still be invoked in original zone.
|
|
|
|
### Error occurs in task lifecycle
|
|
|
|
|