Swift - 在课堂上为自己分配一个 NIB

Question

我正在为通知下拉横幅创建一个 UIView 子类。 我正在使用 XIB 构建视图，并希望在初始化时将该 xib 分配给类（即避免必须从调用 ViewController 执行此操作）。

由于您无法快速分配给“self”，我如何在类本身中正确执行此操作？

class MyDropDown: UIView
{
     func showNotification()
     {
          self = UINib(nibName: nibNamed, bundle: bundle).instantiateWithOwner(nil, options: nil)[0] as? UIView
     }
}

Answer 1

对于任何想在 swift 中从它自己的类初始化 xib 的人，这里是使用自定义类初始化器的最佳方法：

class MyCustomView: UIView
{
    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var titleLabel: UILabel!

    class func initWithTitle(title: String, image: UIImage? = nil) -> MyCustomView
    {
        var myCustomView = UINib(nibName: "MyCustomView", bundle: nil).instantiateWithOwner(nil, options: nil)[0] as? MyCustomView

        myCustomView.titleLabel.text = title

        if image != nil
        {
            myCustomView.imageView.image = image
        }

        //...do other customization here...
        return myCustomView
    }
}

Answer 2

我通常的做法是：

1. 在笔尖中将我的自定义视图类设置为FileOwner
2. 设置所有必需的出口和操作
3. 在 nib 中为视图设置 outlet 并在类中将其命名为 'contentView'
4. 在init* 方法中 - 使用所有者实例化 nib 并将子视图添加到我的自定义视图对象。

这是以这种方式实现的集合标题视图的示例。

@interface Header : UITableViewHeaderFooterView

@property (nonatomic) IBOutlet UIView *contentView;

@property (weak, nonatomic) IBOutlet UILabel *labelTitle;
// other required outlets & actions
// ... 

@end


#import "Header.h"

@implementation Header

- (id)initWithReuseIdentifier:(NSString *)reuseIdentifier
{
    if (self = [super initWithReuseIdentifier:reuseIdentifier]) {
        [[NSBundle mainBundle] loadNibNamed:@"Header"
                                      owner:self
                                    options:nil];
        [self.contentView addSubview:self.content];

        UIView *subview = self.content;
        self.content.translatesAutoresizingMaskIntoConstraints  = NO;
        NSDictionary *viewsDictionary =  NSDictionaryOfVariableBindings(subview);
        [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[subview]|" options:0 metrics: 0 views:viewsDictionary]];
        [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[subview]|" options:0 metrics: 0 views:viewsDictionary]];

    }
    return self;
}

@end

// 更新 Swift 示例

主要思想不是将视图从笔尖直接加载到self，而是将它/视图从笔尖/作为子视图添加到self

import UIKit

class CustomView: UIView {

    @IBOutlet var contentView: UIView!
    @IBOutlet weak var labelTitle: UILabel!

    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.__loadContent()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        self.__loadContent()
    }

    private func __loadContent() {
        // create nib
        let nib = UINib(nibName: "CustomView", bundle: NSBundle.mainBundle())
        // load outlets to self
        nib.instantiateWithOwner(self, options: nil)
        // add content view as a subview
        self.addSubview(self.contentView)
        // disable autoresizing
        self.contentView.setTranslatesAutoresizingMaskIntoConstraints(false)
        // manually create constraints to fix content view inside self with 0 padding
        let viewsDict: NSDictionary = ["content": self.contentView]
        let vertical = NSLayoutConstraint.constraintsWithVisualFormat("V:|[content]|",
            options: NSLayoutFormatOptions.allZeros,
            metrics: nil,
            views: viewsDict)
        let horizontal = NSLayoutConstraint.constraintsWithVisualFormat("H:|[content]|",
            options: NSLayoutFormatOptions.allZeros,
            metrics: nil, views: viewsDict)
        self.addConstraints(vertical)
        self.addConstraints(horizontal)
    }
}