Assign xib to the UIView in Swift

问题:

in objective c it can be done in init method by

-(id)init{
    self = [[[NSBundle mainBundle] loadNibNamed:@"ViewBtnWishList" owner:0 options:nil]     objectAtIndex:0];
return self;
}

but when i do this in swift

init(frame: CGRect) {
    self = NSBundle.mainBundle().loadNibNamed("ViewDetailMenu", owner: 0, options: nil)[0] as? UIView
}

cannot assign to self in a method error is shown. now my approach is to create a view, and add the view loaded from nib to it. anyone have a better idea?

回答1:

for Swift 4

extension UIView {
    class func loadFromNibNamed(nibNamed: String, bundle: Bundle? = nil) -> UIView? {
      return UINib(
          nibName: nibNamed,
          bundle: bundle
      ).instantiate(withOwner: nil, options: nil)[0] as? UIView
  }
}

for Swift 3

You could create an extension on UIView:

extension UIView {
    class func loadFromNibNamed(nibNamed: String, bundle: NSBundle? = nil) -> UIView? {
        return UINib(
            nibName: nibNamed,
            bundle: bundle
        ).instantiateWithOwner(nil, options: nil)[0] as? UIView
    }
}

Note: Using UINib is faster because it does caching for you.

Then you can just do:

ViewDetailItem.loadFromNibNamed("ViewBtnWishList")

And you will be able to reuse that method on any view.

回答2:

Tested in Xcode 7 beta 4 , Swift 2.0 . The following code will assign xib to the UIView. You can use this custom xib view in storyboard and access the IBOutlet object also.

import UIKit

@IBDesignable class SimpleCustomView:UIView
{
    var view:UIView!;

    @IBOutlet weak var lblTitle: UILabel!

   @IBInspectable var lblTitleText : String?
        {
        get{
            return lblTitle.text;
        }
        set(lblTitleText)
        {
            lblTitle.text = lblTitleText!;
        }
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        loadViewFromNib ()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        loadViewFromNib ()
    }
    func loadViewFromNib() {
        let bundle = NSBundle(forClass: self.dynamicType)
        let nib = UINib(nibName: "SimpleCustomView", bundle: bundle)
        let view = nib.instantiateWithOwner(self, options: nil)[0] as! UIView
        view.frame = bounds
        view.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
        self.addSubview(view);



    }


}

Access customview programatically

self.customView =  SimpleCustomView(frame: CGRectMake(100, 100, 200, 200))
        self.view.addSubview(self.customView!);

Source code - https://github.com/karthikprabhuA/CustomXIBSwift

回答3:

This worked for me.

override func awakeAfterUsingCoder(aDecoder: NSCoder) -> AnyObject? {
    if self.subviews.count == 0 {
        return loadNib()
    }
    return self
}

private func loadNib() -> YourCustomView {
    return NSBundle.mainBundle().loadNibNamed("YourCustomViewNibName", owner: nil, options: nil)[0] as YourCustomView
}

回答4:

that may be a solution for you:

Swift 3.x

class func instanceFromNib() -> UIView {
    return UINib(nibName: "<<NibFileName>>", bundle: nil).instantiate(withOwner: nil, options: nil)[0] as! UIView
}

---

Swift 2.x

class func instanceFromNib() -> UIView {
    return UINib(nibName: "<<NibFileName>>", bundle: nil).instantiateWithOwner(nil, options: nil)[0] as UIView
}

回答5:

I think this is the easies but also the cleanest way to assign a xib to a UIView. Xcode 7.3 and swift 2.0.

import UIKit

//Create CustomView class
class CustomView: UIView {

    class func instanceFromNib() -> UIView {
        return UINib(nibName: "CustomView", bundle: nil).instantiateWithOwner(nil, options: nil)[0] as! UIView
    }
}

//Use it
let customView = CustomView.instanceFromNib() as! CustomView

回答6:

The true Swift approach is the use of protocols and protocol extensions.

I use it like this: To start I create a protocol

    protocol XibInitializable {
        static var name: String { get }
        static var bundle: Bundle? { get }

        static func fromXib() -> Self
    }

then I make a default implementation of this protocol use protocol extention

extension XibInitializable where Self : UIView {
    static var name: String {
        return String(describing: Self.self)
    }

    static var bundle: Bundle? {
        return nil
    }

    static func fromXib() -> Self {
        return UINib(nibName: name, bundle: bundle).instantiate(withOwner: nil, options: nil)[0] as! Self
    }
}

the implementation of our protocol is now complete

In order for this protocol to work, you need the name of our xib file and the class were the same. For example, for example

finally add the protocol and make your class "final", like here.

That's it

and use

回答7:

instead of adding an extension to UIView, you could define a protocol and add the implementation to a protocol extension. You can then declare that UIView conforms to the protocol.

This allows the return type to be Self instead of UIView. So the caller doesn't have to cast to the class.

Explained here: https://stackoverflow.com/a/33424509/845027

import UIKit

protocol UIViewLoading {}
extension UIView : UIViewLoading {}

extension UIViewLoading where Self : UIView {

  // note that this method returns an instance of type `Self`, rather than UIView
  static func loadFromNib() -> Self {
    let nibName = "\(self)".characters.split{$0 == "."}.map(String.init).last!
    let nib = UINib(nibName: nibName, bundle: nil)
    return nib.instantiateWithOwner(self, options: nil).first as! Self
  }

}

回答8:

Just made a UINib extension to load a view from xib and embed into a container view using constraints, using generics and strong naming (without using Strings, assuming you have the same file name for xib and implementation):

extension UINib {

    static func instantiateViewAndEmbedWithConstraints <T: UIView> (viewType viewType: T.Type, embedInto containerView: UIView) -> T {
        let view = UINib(nibName: String(viewType), bundle: nil).instantiateWithOwner(nil, options: nil).first as! T
        containerView.addSubview(view)
        view.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint(item: view, attribute: .Leading, relatedBy: .Equal, toItem: containerView, attribute: .Leading, multiplier: 1, constant: 0).active = true
        NSLayoutConstraint(item: view, attribute: .Trailing, relatedBy: .Equal, toItem: containerView, attribute: .Trailing, multiplier: 1, constant: 0).active = true
        NSLayoutConstraint(item: view, attribute: .Top, relatedBy: .Equal, toItem: containerView, attribute: .Top, multiplier: 1, constant: 0).active = true
        NSLayoutConstraint(item: view, attribute: .Bottom, relatedBy: .Equal, toItem: containerView, attribute: .Bottom, multiplier: 1, constant: 0).active = true
        return view
    }

}

Usage:

...outlets...
@IBOutlet var containerView: UIView!
var customView: CustomView!

...viewDidLoad...
customView = UINib.instantiateViewAndEmbedWithConstraints(viewType: CustomView.self, embedInto: containerView)