Diffusion Apple API  6.3.3
Unified Client Library for iOS, tvOS and OS X / macOS
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PTDiffusionUpdateConstraint Class Reference

Introduction

A constraint to be applied to an update operation or the creation of an update stream.

Constraints describe a condition that must be satisfied for an operation to succeed. Constraints can be applied to the setting of a value or creation of an update stream. Constraints are only evaluated on the server.

Constraints are evaluated using the:

The value of a topic can be described in several ways. The value can be described as an exact value, a partial value or an unset value.

Constraints can be composed with one another. It is only possible to construct logical ANDs of constraints. Constraints can only be composed if the resulting constraint is satisfiable. Multiple session locks can be held but a topic can only have a single value. Constraints specifying multiple topic values cannot be constructed.

See Also
PTDiffusionTopicUpdateFeature
Since
6.3
Inheritance diagram for PTDiffusionUpdateConstraint:
PTDiffusionPartialJSONUpdateConstraint

Class Methods

(instancetype) + NS_UNAVAILABLE
 
(instancetype) + lockedWithLock:
 
(instancetype) + noValue
 
(instancetype) + noTopic
 
(PTDiffusionPartialJSONUpdateConstraint *) + jsonValue
 

Instance Methods

(instancetype) - NS_UNAVAILABLE
 
(nullable instancetype) - andConstraint:error:
 

Method Documentation

- (nullable instancetype) andConstraint: (PTDiffusionUpdateConstraint *)  constraint
error: (NSError **)  error 

Returns a composed constraint that represents a logical AND of this constraint and another.

Parameters
constraintThe other constraint that will be logically-ANDed with this constraint
errorLocation to store a reason in case of failure. May be nil.
Returns
A new constraint or nil if there was an error.
Exceptions
NSInvalidArgumentExceptionIf the constraint argument is nil.
Since
6.3

Returns a constraint that partially matches the current topic value.

The topic must be PTDiffusionTopicType_JSON. The returned constraint partially describes the structure of a PTDiffusionJSON value.

Since
6.3
+ (instancetype) lockedWithLock: (PTDiffusionSessionLock *)  lock

Returns a constraint requiring a lock to be held by the session.

This can be used to coordinate operations between multiple sessions.

Exceptions
NSInvalidArgumentExceptionIf the lock argument is nil.
Since
6.3
+ (instancetype) noTopic

Returns a constraint requiring the path to have no topic.

This is useful when setting the first value of a topic being added using one of the 'add and set' methods without changing the value if the topic already exists. This constraint is unsatisfied if a topic is present at the path, making it unsuitable for operations that try to set topics without adding them.

Since
6.3
+ (instancetype) noValue

Create a constraint requiring the topic to have no value.

This is useful when setting the first value of a topic. This constraint is unsatisfied if no topic is present at the path, making it unsuitable for operations that try to add topics.

Since
6.3