How to add constraints programmatically using Swift
Solution 1
Do you plan to have a squared UIView
of width: 100 and Height: 100 centered inside the UIView
of an UIViewController
? If so, you may try one of the 6 following Auto Layout styles (Swift 5 / iOS 12.2):
1. Using NSLayoutConstraint
initializer
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
let widthConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.width, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
let heightConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
view.addConstraints([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
let widthConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.width, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
let heightConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.width, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100).isActive = true
NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100).isActive = true
}
2. Using Visual Format Language
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let views = ["view": view!, "newView": newView]
let horizontalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterY, metrics: nil, views: views)
let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterX, metrics: nil, views: views)
view.addConstraints(horizontalConstraints)
view.addConstraints(verticalConstraints)
}
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let views = ["view": view!, "newView": newView]
let horizontalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterY, metrics: nil, views: views)
let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterX, metrics: nil, views: views)
NSLayoutConstraint.activate(horizontalConstraints)
NSLayoutConstraint.activate(verticalConstraints)
}
3. Using a mix of NSLayoutConstraint
initializer and Visual Format Language
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let views = ["newView": newView]
let widthConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
let heightConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
view.addConstraints(widthConstraints)
view.addConstraints(heightConstraints)
view.addConstraints([horizontalConstraint, verticalConstraint])
}
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let views = ["newView": newView]
let widthConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
let heightConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
NSLayoutConstraint.activate(widthConstraints)
NSLayoutConstraint.activate(heightConstraints)
NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint])
}
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let views = ["newView": newView]
let widthConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
let heightConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
NSLayoutConstraint.activate(widthConstraints)
NSLayoutConstraint.activate(heightConstraints)
NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0).isActive = true
}
4. Using UIView.AutoresizingMask
Note: Springs and Struts will be translated into corresponding auto layout constraints at runtime.
override func viewDidLoad() {
let newView = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = true
newView.center = CGPoint(x: view.bounds.midX, y: view.bounds.midY)
newView.autoresizingMask = [UIView.AutoresizingMask.flexibleLeftMargin, UIView.AutoresizingMask.flexibleRightMargin, UIView.AutoresizingMask.flexibleTopMargin, UIView.AutoresizingMask.flexibleBottomMargin]
}
5. Using NSLayoutAnchor
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let horizontalConstraint = newView.centerXAnchor.constraint(equalTo: view.centerXAnchor)
let verticalConstraint = newView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
let widthConstraint = newView.widthAnchor.constraint(equalToConstant: 100)
let heightConstraint = newView.heightAnchor.constraint(equalToConstant: 100)
view.addConstraints([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let horizontalConstraint = newView.centerXAnchor.constraint(equalTo: view.centerXAnchor)
let verticalConstraint = newView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
let widthConstraint = newView.widthAnchor.constraint(equalToConstant: 100)
let heightConstraint = newView.heightAnchor.constraint(equalToConstant: 100)
NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}
override func viewDidLoad() {
let newView = UIView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
newView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
newView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
newView.widthAnchor.constraint(equalToConstant: 100).isActive = true
newView.heightAnchor.constraint(equalToConstant: 100).isActive = true
}
6. Using intrinsicContentSize
and NSLayoutAnchor
import UIKit
class CustomView: UIView {
override var intrinsicContentSize: CGSize {
return CGSize(width: 100, height: 100)
}
}
class ViewController: UIViewController {
override func viewDidLoad() {
let newView = CustomView()
newView.backgroundColor = UIColor.red
view.addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false
let horizontalConstraint = newView.centerXAnchor.constraint(equalTo: view.centerXAnchor)
let verticalConstraint = newView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint])
}
}
Result:
Solution 2
It helps me to learn visually, so this is a supplemental answer.
Boilerplate code
override func viewDidLoad() {
super.viewDidLoad()
let myView = UIView()
myView.backgroundColor = UIColor.blue
myView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(myView)
// Add constraints code here
// ...
}
Each of the following examples are independent of the others.
Pin left edge
myView.leading = leadingMargin + 20
Method 1: Anchor Style
let margins = view.layoutMarginsGuide
myView.leadingAnchor.constraint(equalTo: margins.leadingAnchor, constant: 20).isActive = true
- In addition to
leadingAnchor
, there is alsotrailingAnchor
,topAnchor
, andbottomAnchor
.
Method 2: NSLayoutConstraint Style
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.leading, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.leadingMargin, multiplier: 1.0, constant: 20.0).isActive = true
- In addition to
.leading
there is also.trailing
,.top
, and.bottom
. - In addition to
.leadingMargin
there is also.trailingMargin
,.topMargin
, and.bottomMargin
.
Set Width and Height
width = 200
height = 100
Method 1: Anchor Style
myView.widthAnchor.constraint(equalToConstant: 200).isActive = true
myView.heightAnchor.constraint(equalToConstant: 100).isActive = true
Method 2: NSLayoutConstraint Style
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 200).isActive = true
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 100).isActive = true
Center in container
myView.centerX = centerX
myView.centerY = centerY
Method 1: Anchor Style
myView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
myView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
Method 2: NSLayoutConstraint Style
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.centerY, multiplier: 1, constant: 0).isActive = true
Notes
- Anchor style is the preferred method over
NSLayoutConstraint
Style, however it is only available from iOS 9, so if you are supporting iOS 8 then you should still useNSLayoutConstraint
Style. - The examples above showed just the one or two constraints that were being focused on. However, in order to properly place
myView
in my test project I needed to have four constraints.
Further Reading
- Programmatically Creating Constraints documentation
Solution 3
If you want to fill your super view then I suggest the swifty way:
view.translatesAutoresizingMaskIntoConstraints = false
let attributes: [NSLayoutAttribute] = [.top, .bottom, .right, .left]
NSLayoutConstraint.activate(attributes.map {
NSLayoutConstraint(item: view, attribute: $0, relatedBy: .equal, toItem: view.superview, attribute: $0, multiplier: 1, constant: 0)
})
Other wise if you need non equal constraints check out NSLayoutAnchor as of iOS 9. Its often much easier to read that using NSLayoutConstraint directly:
view.translatesAutoresizingMaskIntoConstraints = false
view.topAnchor.constraint(equalTo: view.superview!.topAnchor).isActive = true
view.bottomAnchor.constraint(equalTo: view.superview!.bottomAnchor).isActive = true
view.leadingAnchor.constraint(equalTo: view.superview!.leadingAnchor, constant: 10).isActive = true
view.trailingAnchor.constraint(equalTo: view.superview!.trailingAnchor, constant: 10).isActive = true
Solution 4
Constraints for multiple views in playground.
swift 3+
var yellowView: UIView!
var redView: UIView!
override func loadView() {
// UI
let view = UIView()
view.backgroundColor = .white
yellowView = UIView()
yellowView.backgroundColor = .yellow
view.addSubview(yellowView)
redView = UIView()
redView.backgroundColor = .red
view.addSubview(redView)
// Layout
redView.translatesAutoresizingMaskIntoConstraints = false
yellowView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
yellowView.topAnchor.constraint(equalTo: view.topAnchor, constant: 20),
yellowView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
yellowView.widthAnchor.constraint(equalToConstant: 80),
yellowView.heightAnchor.constraint(equalToConstant: 80),
redView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -20),
redView.trailingAnchor.constraint(equalTo: view.trailingAnchor,constant: -20),
redView.widthAnchor.constraint(equalToConstant: 80),
redView.heightAnchor.constraint(equalToConstant: 80)
])
self.view = view
}
In my opinion xcode playground is the best place for learning adding constraints programmatically.
Solution 5
We can easily do this with in swift 5.1
setup 1
- subview align to view center
-
subview width height set using float
view.addSubview(myView1) myView1.translatesAutoresizingMaskIntoConstraints = false NSLayoutConstraint.activate([ myView1.centerXAnchor.constraint(equalTo: view.centerXAnchor), myView1.centerYAnchor.constraint(equalTo: view.centerYAnchor), myView1.widthAnchor.constraint(equalToConstant: 100), myView1.heightAnchor.constraint(equalToConstant: 100), ])
setup 2
- subview align to view leading and top anchor
-
subview width set using view width height
view.addSubview(myView2) myView2.translatesAutoresizingMaskIntoConstraints = false NSLayoutConstraint.activate([ myView2.leadingAnchor.constraint(equalTo: view.leadingAnchor,constant: 16), myView2.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor,constant: 16), myView2.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.3), myView2.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.3) ])
Sara Canducci
Nothing much to say about me...creative arts are my life! Have questions about computer programming, photography, video making or editing? Just ask, I'll be glad to answer! :)
Updated on February 16, 2021Comments
-
Sara Canducci about 3 years
I'm trying to figure this out since last week without going any step further. Ok, so I need to apply some constraints programmatically in Swift to a
UIView
using this code:var new_view:UIView! = UIView(frame: CGRectMake(0, 0, 100, 100)); new_view.backgroundColor = UIColor.redColor(); view.addSubview(new_view); var constX:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0); self.view.addConstraint(constX); var constY:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0); self.view.addConstraint(constY); var constW:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Width, multiplier: 1, constant: 0); self.view.addConstraint(constW); var constH:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Height, multiplier: 1, constant: 0); self.view.addConstraint(constH);
But Xcode returns this weird output:
2014-10-03 09:48:12.657 Test[35088:2454916] Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) ( "<NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX>", "<NSAutoresizingMaskLayoutConstraint:0x7fa4ea4516c0 h=--& v=--& UIView:0x7fa4ea429290.midX == + 50>", "<NSLayoutConstraint:0x7fa4ea452830 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7fa4ea4470f0(375)]>", "<NSAutoresizingMaskLayoutConstraint:0x7fa4ea446db0 h=-&- v=-&- 'UIView-Encapsulated-Layout-Left' H:|-(0)-[UIView:0x7fa4ea4470f0] (Names: '|':UIWindow:0x7fa4ea444b20 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX> Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful. 2014-10-03 09:48:12.658 Test[35088:2454916] Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) ( "<NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY>", "<NSAutoresizingMaskLayoutConstraint:0x7fa4ea451b30 h=--& v=--& UIView:0x7fa4ea429290.midY == + 50>", "<NSLayoutConstraint:0x7fa4ea44cf00 'UIView-Encapsulated-Layout-Height' V:[UIView:0x7fa4ea4470f0(667)]>", "<NSAutoresizingMaskLayoutConstraint:0x7fa4ea452700 h=-&- v=-&- 'UIView-Encapsulated-Layout-Top' V:|-(0)-[UIView:0x7fa4ea4470f0] (Names: '|':UIWindow:0x7fa4ea444b20 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY> Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
Can you help me? Thanks a lot