The priority level with which the view wants to conform to the target size in that computation.
When you send a
systemLayoutSizeFitting(_:) message to a view, the size fitting most closely to the target size is computed. This priority is quite low. It is generally not appropriate to make a constraint at exactly this priority. You want to be higher or lower.
Getting the Layout Priority
The layout priority is used to indicate to the constraint-based layout system which constraints are more important, allowing the system to make appropriate tradeoffs when satisfying the constraints of the system as a whole.
Layout priority used to indicate the relative importance of constraints, allowing Auto Layout to make appropriate tradeoffs when satisfying the constraints of the system as a whole.