ORKStep Class Reference

Inherits from NSObject
Conforms to NSCopying
NSSecureCoding
Declared in ORKStep.h

ORKStep is the base class for the steps that can compose a task for presentation in an ORKTaskViewController object. Each ORKStep object represents one logical piece of data entry or activity in a larger task.

A step can be a question, an active test, or a simple instruction. An ORKStep subclass is usually paired with an ORKStepViewController subclass that displays the step.

To use a step, instantiate an ORKStep object and populate its properties. Add the step to a task, such as an ORKOrderedTask object, and then present the task using a task view controller (an ORKTaskViewController object).

To implement a new type of step, subclass ORKStep and add your additional properties. Separately, subclass ORKStepViewController and implement your user interface. Note that if your step is timed or requires sensor data collection, you should consider subclassing ORKActiveStep and ORKActiveStepViewController instead.

– initWithIdentifier:

Returns a new step initialized with the specified identifier.

- (instancetype)initWithIdentifier:(NSString *)identifier

Parameters

identifier

The unique identifier of the step.

Return Value

A new step.

Discussion

This method is the primary designated initializer.

Declared In

ORKStep.h

– initWithCoder:

Returns a new step initialized from data in the given unarchiver.

- (instancetype)initWithCoder:(NSCoder *)aDecoder

Parameters

aDecoder

Coder from which to initialize the step.

Return Value

A new step.

Declared In

ORKStep.h

  identifier

A short string that uniquely identifies the step within the task.

@property (nonatomic, copy, readonly) NSString *identifier

Discussion

The identifier is reproduced in the results of a step. In fact, the only way to link a result (an ORKStepResult object) to the step that generated it is to look at the value of identifier. To accurately identify step results, you need to ensure that step identifiers are unique within each task.

In some cases, it can be useful to link the step identifier to a unique identifier in a database; in other cases, it can make sense to make the identifier human readable.

Declared In

ORKStep.h

  restorable

A Boolean value indicating whether a task can be restored to the step during state restoration. (read-only)

@property (nonatomic, readonly, getter=isRestorable) BOOL restorable

Discussion

By default, the value of this property is YES, but subclasses of ORKStep might use NO.

If a task cannot be restored to the step, the task is typically restored to the last restorable step in the task, or to the first step, if no restorable steps are available.

Declared In

ORKStep.h

  optional

A Boolean value indicating whether the user can skip the step without providing an answer.

@property (nonatomic, getter=isOptional) BOOL optional

Discussion

The default value of this property is YES. When the value is NO, the Skip button does not appear on this step.

This property may not be meaningful for all steps; for example, an active step might not provide a way to skip, because it requires a timer to finish.

Declared In

ORKStep.h

  title

The primary text to display for the step in a localized string.

@property (nonatomic, copy, nullable) NSString *title

Declared In

ORKStep.h

  text

Additional text to display for the step in a localized string.

@property (nonatomic, copy, nullable) NSString *text

Discussion

The additional text is displayed in a smaller font below title. If you need to display a long question, it can work well to keep the title short and put the additional content in the text property.

Declared In

ORKStep.h

  task

The task that contains the step.

@property (nonatomic, weak, nullable) id<ORKTask> task

Discussion

The value of task is usually set when a step is added to the ORKOrderedTask object. Although it’s a good idea to set this property when you implement a custom task, it’s important to note that the use of this property is a convenience, and should not be relied upon within the ResearchKit framework.

Declared In

ORKStep.h

  requestedPermissions

The set of access permissions required for the step. (read-only)

@property (nonatomic, readonly) ORKPermissionMask requestedPermissions

Discussion

The permission mask is used by the task view controller to determine the types of access to request from users when they complete the initial instruction steps in a task. If your step requires access to APIs that limit access, include the permissions you require in this mask.

By default, the property scans the recorders and collates the permissions required by the recorders. Subclasses may override this implementation.

Declared In

ORKStep.h

– validateParameters

Checks the parameters of the step and throws exceptions on invalid parameters.

- (void)validateParameters

Discussion

This method is called when there is a need to validate the step’s parameters, which is typically the case when adding a step to an ORKStepViewController object, and when presenting the step view controller.

Subclasses should override this method to provide validation of their additional properties, and must call super.

Declared In

ORKStep.h