In Swift 3 (XCode 8.3.3) I have a control in a UIStackView. I have an array of UIImageViews, and loop through the array to populate the stack view at run time:
for voiceIcon in voiceIcons {
let voiceView = UIImageView(image: voiceIcon)
addArrangedSubview(voiceView)
}
These icons will sometimes become disabled (replaced with a new image), so in order to update the control, I have a function to remove all the icons so that I can re-add the appropriate ones (if there's a better way, I'm listening!):
private func resetIconsView() {
for subUIView in self.subviews as [UIView] {
removeArrangedSubview(subUIView)
subUIView.removeFromSuperview()
print("Removing")
}
}
I've also tried
for subUIView in self.subviews as! [UIImageView] { ... }
I get the debug line "Removing" for each of the icons, but they still remain in the control and the UI. I'm new to Swift, so I'm likely not understanding something, what approach should I take?
Try code below:
for view in arrangedSubviews {
view.removeFromSuperview()
}
I am assuming your UIStackView only contains some UIImageView. You can iterate through all the arranged subviews of your stack view and update your image of that imageView. A sample implementation could look like below:
func changeImage() {
for view in self.arrangedSubviews {
if let imgView = view as? UIImageView {
imgView.image = UIImage(named: "taka_icon.png")
}
}
}
I did it with an extension. You have also to remove Constraints if existing. Else this can cause some trouble.
USAGE: myStackView.removeAllArrangedSubviews()
public extension UIStackView {
func removeAllArrangedSubviews() {
let removedSubviews = arrangedSubviews.reduce([]) { (allSubviews, subview) -> [UIView] in
self.removeArrangedSubview(subview)
return allSubviews + [subview]
}
// Deactivate all constraints
NSLayoutConstraint.deactivate(removedSubviews.flatMap({ $0.constraints }))
// Remove the views from self
removedSubviews.forEach({ $0.removeFromSuperview() })
}
}
for progressView:UIView in cell.IBimgCellImage.subviews as UIView{
//do something
}
But getting error,
Type 'UIView' does not conform to protocol 'SequenceType'
Is there any way to get rid of it?
You cast is wrong, subviews is an array of UIView, so use [UIView]
for progressView:UIView in cell.IBimgCellImage.subviews as [UIView] {
//do something
}
I would suggest this simplier approach:
for progressView in cell.IBimgCellImage.subviews {
let aSubView = progressView as? UIView
//do the work
}
Swift 5. In this instance, it's okay to force unwrap parent because it's known that the parent UIViewController will not be nil. It also removes the need to force cast to a [UIView].
for subview in parent!.view.subviews {
// perform action
}
Here's an example:
for subview in parent!.view.subviews {
if subview is UIButton {
subview.isHidden = false
}
}
I am trying to find the current focused First Responder by looping through the main UIView and all of it's SubViews, and all of it's SubViews through recursion, but I am coming up with nil.
extension UIView {
func getCurrentFirstResponder() -> AnyObject? {
if self.isFirstResponder() {
return self
}
for subView: UIView in self.subviews as [UIView] {
if subView.isFirstResponder() {
return subView
}
else {
subView.getCurrentFirstResponder()
}
}
return nil
}
}
let focusedView = self.view.getCurrentFirstResponder() as? UIView
Does this look correct? Why am I getting a nil view when I use this?
You code doesn't return anything in case the recursive call to subView.getCurrentFirstResponder() actually finds a first responder.
Try this:
for subView: UIView in self.subviews as [UIView] {
if subView.isFirstResponder() {
return subView
}
else {
if let sub = subView.getCurrentFirstResponder() {
return sub;
}
}
}
return nil
I"m wondering how to essentially transform the objective c code below into swift.
This will loop through all the subviews on my desired view, check if they are textfields, and then check if they are empty of not.
for (UIView *view in contentVw.subviews) {
NSLog(#"%#", view);
if ([view isKindOfClass:[UITextField class]]) {
UITextField *textfield = (UITextField *)view;
if (([textfield.text isEqualToString:""])) {
//show error
return;
}
}
}
Here is where i am with swift translation so far:
for view in self.view.subviews as [UIView] {
if view.isKindOfClass(UITextField) {
//...
}
}
Any help would be great!
Update for Swift 2 (and later): As of Swift 2/Xcode 7 this can be simplified.
Due to the Objective-C "lightweight generics", self.view.subviews
is already declared as [UIView] in Swift, therefore the cast
is not necessary anymore.
Enumeration and optional cast can be combined with to a for-loop
with a case-pattern.
This gives:
for case let textField as UITextField in self.view.subviews {
if textField.text == "" {
// show error
return
}
}
Old answer for Swift 1.2:
In Swift this is nicely done with the optional downcast operator as?:
for view in self.view.subviews as! [UIView] {
if let textField = view as? UITextField {
if textField.text == "" {
// show error
return
}
}
}
See "Downcasting"
in the Swift book.
Swift 5 and Swift 4: -
A Very simple answer you can understand easyly : - You can handle all kind of Objects like UILable, UITextfields, UIButtons, UIView, UIImages . any kind of objecs etc.
for subview in self.view.subviews
{
if subview is UITextField
{
//MARK: - if the sub view is UITextField you can handle here
if subview.text == ""
{
//MARK:- Handle your code
}
}
if subview is UIImageView
{
//MARK: - check image
if subview.image == nil
{
//Show or use your code here
}
}
}
//MARK:- You can use it any where, where you need it
//Suppose i need it in didload function we can use it and work it what do you need
override func viewDidLoad() {
super.viewDidLoad()
for subview in self.view.subviews
{
if subview is UITextField
{
//MARK: - if the sub view is UITextField you can handle here
if subview.text == ""
{
//MARK:- Handle your code
}
}
if subview is UIImageView
{
//MARK: - check image
if subview.image == nil
{
//Show or use your code here
}
}
}
}
I have a UIView which is placed on the screen via several constraints. Some of the constraints are owned by the superview, others are owned by other ancestors (e.g. perhaps the view property of a UIViewController).
I want to remove all of these old constraints, and place it somewhere new using new constraints.
How can I do this without creating an IBOutlet for every single constraint and having to remember which view owns said constraint?
To elaborate, the naive approach would be to create a bunch of IBOutlets for each of the constraints, and would then involve calling code such as:
[viewA removeConstraint:self.myViewsLeftConstraint];
[viewB removeConstraint:self.myViewsTopConstraint];
[viewB removeConstraint:self.myViewsBottomConstraint];
[self.view removeConstraint:self.myViewsRightConstraint];
The problem with this code is that even in the simplest case, I would need to create 2 IBOutlets. For complex layouts, this could easily reach 4 or 8 required IBOutlets. Furthermore, I would need to ensure that my call to remove the constraint is being called on the proper view. For example, imagine that myViewsLeftConstraint is owned by viewA. If I were to accidentally call [self.view removeConstraint:self.myViewsLeftConstraint], nothing would happen.
Note: The method constraintsAffectingLayoutForAxis looks promising, but is intended for debugging purposes only.
Update: Many of the answers I am receiving deal with self.constraints, self.superview.constraints, or some variant of those. These solutions won't work since those methods return only the constraints owned by the view, not the ones affecting the view.
To clarify the problem with these solutions, consider this view hierarchy:
Grandfather
Father
Me
Son
Daughter
Brother
Uncle
Now imagine we create the following constraints, and always attach them to their nearest common ancestor:
C0: Me: same top as Son (owned by Me)
C1: Me: width = 100 (owned by Me)
C2: Me: same height as Brother (owned by Father)
C3: Me: same top as Uncle (owned by Grandfather)
C4: Me: same left as Grandfather (owned by Grandfather)
C5: Brother: same left as Father (owned by Father)
C6: Uncle: same left as Grandfather (owned by Grandfather)
C7: Son: same left as Daughter (owned by Me)
Now imagine we want to remove all constraints affecting Me. Any proper solution should remove [C0,C1,C2,C3,C4] and nothing else.
If I use self.constraints (where self is Me), I will get [C0,C1,C7], since those are the only constraints owned by Me. Obviously it wouldn't be enough to remove this since it is missing [C2,C3,C4]. Furthermore, it is removing C7 unnecessarily.
If I use self.superview.constraints (where self is Me), I will get [C2,C5], since those are the constraints owned by Father. Obviously we cannot remove all these since C5 is completely unrelated to Me.
If I use grandfather.constraints, I will get [C3,C4,C6]. Again, we cannot remove all of these since C6 should remain intact.
The brute force approach is to loop over each of the view's ancestors (including itself), and seeing if firstItem or secondItem are the view itself; if so, remove that constraint. This will lead to a correct solution, returning [C0,C1,C2,C3,C4], and only those constraints.
However, I'm hoping there is a more elegant solution than having to loop through the entire list of ancestors.
This approach worked for me:
#interface UIView (RemoveConstraints)
- (void)removeAllConstraints;
#end
#implementation UIView (RemoveConstraints)
- (void)removeAllConstraints
{
UIView *superview = self.superview;
while (superview != nil) {
for (NSLayoutConstraint *c in superview.constraints) {
if (c.firstItem == self || c.secondItem == self) {
[superview removeConstraint:c];
}
}
superview = superview.superview;
}
[self removeConstraints:self.constraints];
self.translatesAutoresizingMaskIntoConstraints = YES;
}
#end
After it's done executing your view remains where it was because it creates autoresizing constraints. When I don't do this the view usually disappears. Additionally, it doesn't just remove constraints from superview but traversing all the way up as there may be constraints affecting it in ancestor views.
Swift 4 Version
extension UIView {
public func removeAllConstraints() {
var _superview = self.superview
while let superview = _superview {
for constraint in superview.constraints {
if let first = constraint.firstItem as? UIView, first == self {
superview.removeConstraint(constraint)
}
if let second = constraint.secondItem as? UIView, second == self {
superview.removeConstraint(constraint)
}
}
_superview = superview.superview
}
self.removeConstraints(self.constraints)
self.translatesAutoresizingMaskIntoConstraints = true
}
}
The only solution I have found so far is to remove the view from its superview:
[view removeFromSuperview]
This looks like it removes all constraints affecting its layout and is ready to be added to a superview and have new constraints attached. However, it will incorrectly remove any subviews from the hierarchy as well, and get rid of [C7] incorrectly.
You can remove all constraints in a view by doing this:
self.removeConstraints(self.constraints)
EDIT: To remove the constraints of all subviews, use the following extension in Swift:
extension UIView {
func clearConstraints() {
for subview in self.subviews {
subview.clearConstraints()
}
self.removeConstraints(self.constraints)
}
}
There are two ways of on how to achieve that according to Apple Developer Documentation
1. NSLayoutConstraint.deactivateConstraints
This is a convenience method that provides an easy way to deactivate a
set of constraints with one call. The effect of this method is the
same as setting the isActive property of each constraint to false.
Typically, using this method is more efficient than deactivating each
constraint individually.
// Declaration
class func deactivate(_ constraints: [NSLayoutConstraint])
// Usage
NSLayoutConstraint.deactivate(yourView.constraints)
2. UIView.removeConstraints (Deprecated for >= iOS 8.0)
When developing for iOS 8.0 or later, use the NSLayoutConstraint
class’s deactivateConstraints: method instead of calling the
removeConstraints: method directly. The deactivateConstraints: method
automatically removes the constraints from the correct views.
// Declaration
func removeConstraints(_ constraints: [NSLayoutConstraint])`
// Usage
yourView.removeConstraints(yourView.constraints)
Tips
Using Storyboards or XIBs can be such a pain at configuring the constraints as mentioned on your scenario, you have to create IBOutlets for each ones you want to remove. Even so, most of the time Interface Builder creates more trouble than it solves.
Therefore when having very dynamic content and different states of the view, I would suggest:
Creating your views programmatically
Layout them and using NSLayoutAnchor
Append each constraint that might get removed later to an array
Clear them every time before applying the new state
Simple Code
private var customConstraints = [NSLayoutConstraint]()
private func activate(constraints: [NSLayoutConstraint]) {
customConstraints.append(contentsOf: constraints)
customConstraints.forEach { $0.isActive = true }
}
private func clearConstraints() {
customConstraints.forEach { $0.isActive = false }
customConstraints.removeAll()
}
private func updateViewState() {
clearConstraints()
let constraints = [
view.leadingAnchor.constraint(equalTo: parentView.leadingAnchor),
view.trailingAnchor.constraint(equalTo: parentView.trailingAnchor),
view.topAnchor.constraint(equalTo: parentView.topAnchor),
view.bottomAnchor.constraint(equalTo: parentView.bottomAnchor)
]
activate(constraints: constraints)
view.layoutIfNeeded()
}
References
NSLayoutConstraint
UIView
In Swift:
import UIKit
extension UIView {
/**
Removes all constrains for this view
*/
func removeConstraints() {
let constraints = self.superview?.constraints.filter{
$0.firstItem as? UIView == self || $0.secondItem as? UIView == self
} ?? []
self.superview?.removeConstraints(constraints)
self.removeConstraints(self.constraints)
}
}
Details
Xcode 10.2.1 (10E1001), Swift 5
Solution
import UIKit
extension UIView {
func removeConstraints() { removeConstraints(constraints) }
func deactivateAllConstraints() { NSLayoutConstraint.deactivate(getAllConstraints()) }
func getAllSubviews() -> [UIView] { return UIView.getAllSubviews(view: self) }
func getAllConstraints() -> [NSLayoutConstraint] {
var subviewsConstraints = getAllSubviews().flatMap { $0.constraints }
if let superview = self.superview {
subviewsConstraints += superview.constraints.compactMap { (constraint) -> NSLayoutConstraint? in
if let view = constraint.firstItem as? UIView, view == self { return constraint }
return nil
}
}
return subviewsConstraints + constraints
}
class func getAllSubviews(view: UIView) -> [UIView] {
return view.subviews.flatMap { [$0] + getAllSubviews(view: $0) }
}
}
Usage
print("constraints: \(view.getAllConstraints().count), subviews: \(view.getAllSubviews().count)")
view.deactivateAllConstraints()
The easier and efficient approach is to remove the view from superView and re add as subview again.
this causes all the subview constraints get removed automagically.😉
Swift
Following UIView Extension will remove all Edge constraints of a view:
extension UIView {
func removeAllConstraints() {
if let _superview = self.superview {
self.removeFromSuperview()
_superview.addSubview(self)
}
}
}
A Swift solution:
extension UIView {
func removeAllConstraints() {
var view: UIView? = self
while let currentView = view {
currentView.removeConstraints(currentView.constraints.filter {
return $0.firstItem as? UIView == self || $0.secondItem as? UIView == self
})
view = view?.superview
}
}
}
It's important to go through all the parents, since the constraints between two elements are holds by the common ancestors, so just clearing the superview as detailed in this answer is not good enough, and you might end up having bad surprise later on.
Based on previous answers (swift 4)
You can use immediateConstraints when you don't want to crawl entire hierarchies.
extension UIView {
/**
* Deactivates immediate constraints that target this view (self + superview)
*/
func deactivateImmediateConstraints(){
NSLayoutConstraint.deactivate(self.immediateConstraints)
}
/**
* Deactivates all constrains that target this view
*/
func deactiveAllConstraints(){
NSLayoutConstraint.deactivate(self.allConstraints)
}
/**
* Gets self.constraints + superview?.constraints for this particular view
*/
var immediateConstraints:[NSLayoutConstraint]{
let constraints = self.superview?.constraints.filter{
$0.firstItem as? UIView === self || $0.secondItem as? UIView === self
} ?? []
return self.constraints + constraints
}
/**
* Crawls up superview hierarchy and gets all constraints that affect this view
*/
var allConstraints:[NSLayoutConstraint] {
var view: UIView? = self
var constraints:[NSLayoutConstraint] = []
while let currentView = view {
constraints += currentView.constraints.filter {
return $0.firstItem as? UIView === self || $0.secondItem as? UIView === self
}
view = view?.superview
}
return constraints
}
}
I use the following method to remove all constraints from a view:
.h file:
+ (void)RemoveContraintsFromView:(UIView*)view
removeParentConstraints:(bool)parent
removeChildConstraints:(bool)child;
.m file:
+ (void)RemoveContraintsFromView:(UIView *)view
removeParentConstraints:(bool)parent
removeChildConstraints:(bool)child
{
if (parent) {
// Remove constraints between view and its parent.
UIView *superview = view.superview;
[view removeFromSuperview];
[superview addSubview:view];
}
if (child) {
// Remove constraints between view and its children.
[view removeConstraints:[view constraints]];
}
}
You can also read this post on my blog to better understand how it works behind the hood.
If you need more granular control, I'd strongly advise switching to Masonry, a powerful framework class you could use whenever you need to properly handle constraints programmatically.
With objectiveC
[self.superview.constraints enumerateObjectsUsingBlock:^(__kindof NSLayoutConstraint * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
NSLayoutConstraint *constraint = (NSLayoutConstraint *)obj;
if (constraint.firstItem == self || constraint.secondItem == self) {
[self.superview removeConstraint:constraint];
}
}];
[self removeConstraints:self.constraints];
}
You could use something like this:
[viewA.superview.constraints enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSLayoutConstraint *constraint = (NSLayoutConstraint *)obj;
if (constraint.firstItem == viewA || constraint.secondItem == viewA) {
[viewA.superview removeConstraint:constraint];
}
}];
[viewA removeConstraints:viewA.constraints];
Basically, this is enumerates over all the constraints on the superview of viewA and removes all of the constraints that are related to viewA.
Then, the second part removes the constraints from viewA using the array of viewA's constraints.
(As of July 31, 2017)
SWIFT 3
self.yourCustomView.removeFromSuperview()
self.yourCustomViewParentView.addSubview(self.yourCustomView)
Objective C
[self.yourCustomView removeFromSuperview];
[self.yourCustomViewParentView addSubview:self.yourCustomView];
This is the easiest way to quickly remove all constraints that exist on a UIView. Just be sure to add the UIView back with it's new constraints or new frame afterwards =)
Using a Reusable Sequence
I decided to approach this in a more 'reusable' way. Since finding all constraints affecting a view is the basis for all of the above, I decided to implement a custom sequence that returns them all for me, along with the owning views.
First thing to do is define an extension on Arrays of NSLayoutConstraint that returns all elements affecting a specific view.
public extension Array where Element == NSLayoutConstraint {
func affectingView(_ targetView:UIView) -> [NSLayoutConstraint] {
return self.filter{
if let firstView = $0.firstItem as? UIView,
firstView == targetView {
return true
}
if let secondView = $0.secondItem as? UIView,
secondView == targetView {
return true
}
return false
}
}
}
We then use that extension in a custom sequence that returns all constraints affecting that view, along with the views that actually own them (which can be anywhere up the view hierarchy)
public struct AllConstraintsSequence : Sequence {
public init(view:UIView){
self.view = view
}
public let view:UIView
public func makeIterator() -> Iterator {
return Iterator(view:view)
}
public struct Iterator : IteratorProtocol {
public typealias Element = (constraint:NSLayoutConstraint, owningView:UIView)
init(view:UIView){
targetView = view
currentView = view
currentViewConstraintsAffectingTargetView = currentView.constraints.affectingView(targetView)
}
private let targetView : UIView
private var currentView : UIView
private var currentViewConstraintsAffectingTargetView:[NSLayoutConstraint] = []
private var nextConstraintIndex = 0
mutating public func next() -> Element? {
while(true){
if nextConstraintIndex < currentViewConstraintsAffectingTargetView.count {
defer{nextConstraintIndex += 1}
return (currentViewConstraintsAffectingTargetView[nextConstraintIndex], currentView)
}
nextConstraintIndex = 0
guard let superview = currentView.superview else { return nil }
self.currentView = superview
self.currentViewConstraintsAffectingTargetView = currentView.constraints.affectingView(targetView)
}
}
}
}
Finally we declare an extension on UIView to expose all the constraints affecting it in a simple property that you can access with a simple for-each syntax.
extension UIView {
var constraintsAffectingView:AllConstraintsSequence {
return AllConstraintsSequence(view:self)
}
}
Now we can iterate all constraints affecting a view and do what we want with them...
List their identifiers...
for (constraint, _) in someView.constraintsAffectingView{
print(constraint.identifier ?? "No identifier")
}
Deactivate them...
for (constraint, _) in someView.constraintsAffectingView{
constraint.isActive = false
}
Or remove them entirely...
for (constraint, owningView) in someView.constraintsAffectingView{
owningView.removeConstraints([constraint])
}
Enjoy!
This is the way to disable all constraints from a specific view
NSLayoutConstraint.deactivate(myView.constraints)