ProgressTracker - corda

corda / net.corda.core.utilities / ProgressTracker

# ProgressTracker

`class ProgressTracker`

A progress tracker helps surface information about the progress of an operation to a user interface or API of some kind. It lets you define a set of steps that represent an operation. A step is represented by an object (typically a singleton).

Steps may logically be children of other steps, which models the case where a large top level operation involves sub-operations which may also have a notion of progress. If a step has children, then the tracker will report the steps children as the "next step" after the parent. In other words, a parent step is considered to involve actual reportable work and is a thing. If the parent step simply groups other steps, then you'll have to step over it manually.

Each step has a label. It is assumed by default that the label does not change. If you want a label to change, then you can emit a ProgressTracker.Change.Rendering object on the ProgressTracker.Step.changes observable stream after it changes. That object will propagate through to the top level trackers changes stream, which renderers can subscribe to in order to learn about progress.

An operation can move both forwards and backwards through steps, thus, a ProgressTracker can represent operations that include loops.

A progress tracker is not thread safe. You may move events from the thread making progress to another thread by using the Observable subscribeOn call.

### Types

#### Change | `sealed class Change`
#### DONE | `object DONE : Step`
#### STARTING | `object STARTING : Step`
#### Step | The superclass of all step objects. `class Step`
#### UNSTARTED | `object UNSTARTED : Step`

### Constructors

#### <init> | A progress tracker helps surface information about the progress of an operation to a user interface or API of some kind. It lets you define a set of steps that represent an operation. A step is represented by an object (typically a singleton). `ProgressTracker(vararg inputSteps: Step)`

### Properties

#### allSteps | A list of all steps in this ProgressTracker and the children, with the indent level provided starting at zero. Note that UNSTARTED is never counted, and DONE is only counted at the calling level. `val allSteps: List<Pair<Int, Step>>`
#### allStepsLabels | A list of all steps label in this ProgressTracker and the children, with the indent level provided starting at zero. Note that UNSTARTED is never counted, and DONE is only counted at the calling level. `val allStepsLabels: List<Pair<Int, String>>`
#### changes | An observable stream of changes: includes child steps, resets and any changes emitted by individual steps (e.g. if a step changed its label or rendering). `val changes: Observable<Change>`
#### currentStep | Reading returns the value of stepsstepIndex, writing moves the position of the current tracker. Once moved to the DONE state, this tracker is finished and the current step cannot be moved again. `var currentStep: Step`
#### currentStepRecursive | Returns the current step, descending into children to find the deepest step we are up to. `val currentStepRecursive: Step`
#### hasEnded | Returns true if the progress tracker has ended, either by reaching the DONE step or prematurely with an error `val hasEnded: Boolean`
#### parent | The parent of this tracker: set automatically by the parent when a tracker is added as a child `var parent: ProgressTracker?`
#### stepIndex | The zero-based index of the current step in the steps array (i.e. with UNSTARTED and DONE) `var stepIndex: Int`
#### steps | The steps in this tracker, same as the steps passed to the constructor but with UNSTARTED and DONE inserted. `val steps: Array<Step>`
#### stepsTreeChanges | An observable stream of changes to the allStepsLabels `val stepsTreeChanges: Observable<List<Pair<Int, String>>>`
#### stepsTreeIndex | The zero-bases index of the current step in a allStepsLabels list `var stepsTreeIndex: Int`
#### stepsTreeIndexChanges | An observable stream of changes to the stepsTreeIndex `val stepsTreeIndexChanges: Observable<Int>`
#### topLevelTracker | Walks up the tree to find the top level tracker. If this is the top level tracker, returns 'this'. Required for API compatibility. `val topLevelTracker: ProgressTracker`

### Functions

#### endWithError | Ends the progress tracker with the given error, bypassing any remaining steps. changes will emit the exception as an error. `fun endWithError(error: Throwable): Unit`
#### getChildProgressTracker | `fun getChildProgressTracker(step: Step): ProgressTracker?`
#### nextStep | Iterates the progress tracker. If the current step has a child, the child is iterated instead (recursively). Returns the latest step at the bottom of the step tree. `fun nextStep(): Step`
#### setChildProgressTracker | `fun setChildProgressTracker(step: Step, childProgressTracker: ProgressTracker): Unit`