Figuring out if a UIViewController’s position is genuinely available is a important facet of iOS improvement. It’s much nuanced than merely checking if the position controller is portion of the position hierarchy. Galore components tin power visibility, from genitor views to the position’s framework and equal disconnected-surface positioning. Knowing these nuances permits builders to optimize show, grip UI updates accurately, and make a much seamless person education. This station volition dive heavy into the assorted strategies and concerns for precisely figuring out position visibility inside your iOS functions.
The isViewLoaded Place: A Beginning Component
The isViewLoaded place is frequently the archetypal cheque builders execute. It signifies whether or not the position controller’s loadView() methodology has been referred to as and the position hierarchy has been instantiated. Nevertheless, it doesn’t warrant visibility connected surface.
See a position controller inside a UINavigationController. Equal if isViewLoaded returns actual, the position mightiness not beryllium available if the position controller isn’t astatine the apical of the navigation stack.
So, isViewLoaded is a essential however inadequate information for actual visibility.
The framework Place: Checking Position Hierarchy Rank
Checking if the position controller’s position.framework place is non-nil is a much dependable indicator of visibility. A non-nil worth suggests the position is portion of the exertion’s framework hierarchy. This is a stronger impressive that the position mightiness beryllium available, however inactive not definitive.
For illustration, the position might beryllium obscured by different position oregon positioned wholly disconnected-surface. Piece technically successful the framework hierarchy, it wouldn’t beryllium available to the person.
Bounds and Framework Geometry: Accounting for Disconnected-Surface Views
Equal with a non-nil position.framework, the position’s framework and bounds drama a critical function. A position with a framework positioned wholly extracurricular its genitor position’s bounds, oregon with zero width/tallness, volition not beryllium available.
To verify visibility, confirm that the intersection of the position’s framework and its genitor position’s bounds is non-bare:
- Cheque that
position.framework.intersects(position.superview?.bounds ?? .zero)returnsactual. - Guarantee
position.framework.dimensionhas non-zero width and tallness.
The alpha Place and Hidden Government: Dealing with Position Opacity and Visibility
The position.alpha place and position.isHidden place straight power visibility. A position with alpha fit to zero oregon isHidden fit to actual gained’t beryllium available, careless of its assumption successful the position hierarchy.
Retrieve to cheque some of these properties once assessing visibility.
Superview Visibility: The Recursive Cheque
A position’s visibility relies upon connected the visibility of its genitor position, and its genitor’s genitor, and truthful connected, each the manner ahead the position hierarchy. A position can’t beryllium available if immoderate of its ancestor views are hidden oregon person zero alpha.
Implementing a recursive relation to traverse the position hierarchy is beneficial for a thorough visibility cheque. This relation ought to cheque isHidden and alpha for all ancestor position.
- Commencement with the position successful motion.
- Cheque its
isHiddenandalphaproperties. - Recursively call the relation connected its
superview. - Halt once you range the apical of the hierarchy (
superview == nil).
Placing it Each Unneurotic: A Blanket Attack
Harvester the checks mentioned supra to make a sturdy visibility cheque. Commencement with the basal isViewLoaded and position.framework properties. Past, delve into framework and bounds geometry, and eventually execute the recursive superview cheque.
This thorough attack volition supply close visibility dedication successful assorted situations.
Infographic Placeholder: Visualizing Position Visibility Checks
[Infographic depicting the antithetic visibility checks and their hierarchy]
FAQ
Q: Does viewDidAppear() warrant visibility?
A: Nary. viewDidAppear() signifies the position has appeared connected surface, however consequent occasions (similar different position controller being introduced) tin obscure it. Usage the strategies outlined supra for existent-clip visibility checks.
Precisely assessing UIViewController position visibility is paramount for responsive and businesslike iOS functions. By incorporating the methods mentioned – from checking basal properties similar isViewLoaded and position.framework to analyzing framework geometry, alpha, hidden position, and performing recursive superview checks – you addition granular power complete your UI and tin grip position-associated logic with precision. This cognition empowers you to make a smoother, much polished person education. Research additional assets similar Pome’s documentation connected UIView and UIViewController to deepen your knowing. Larn much astir precocious UIViewController direction to heighten your iOS improvement abilities. Besides, mention to these outer assets: Pome’s UIView Documentation, Pome’s UIViewController Documentation, and Ray Wenderlich Tutorials. Commencement implementing these strategies present and seat the quality they brand successful your iOS tasks!
Question & Answer :
I person a tab barroom exertion, with galore views. Is location a manner to cognize if a peculiar UIViewController is presently available from inside the UIViewController? (wanting for a place)
The position’s framework place is non-nil if a position is presently available, truthful cheque the chief position successful the position controller:
Invoking the position methodology causes the position to burden (if it is not loaded) which is pointless and whitethorn beryllium undesirable. It would beryllium amended to cheque archetypal to seat if it is already loaded. I’ve added the call to isViewLoaded to debar this job.
if (viewController.isViewLoaded && viewController.position.framework) { // viewController is available }
Since iOS9 it has grew to become simpler:
if viewController.viewIfLoaded?.framework != nil { // viewController is available }
Oregon if you person a UINavigationController managing the position controllers, you may cheque its visibleViewController place alternatively.
