使用xib创建可重用的UIView（并从storyboard加载）

问题描述

好的，StackOverflow上有很多关于此的帖子，但没有一个在解决方案上特别清楚。我想用附带的xib文件创建一个自定义 UIView 。要求是：

OK, there are dozens of posts on StackOverflow about this, but none are particularly clear on the solution. I'd like to create a custom UIView with an accompanying xib file. The requirements are:

• 没有单独的 UIViewController - 一个完全独立的类


• 允许我设置/获取视图属性的类中的插座

• No separate UIViewController – a completely self-contained class
• Outlets in the class to allow me to set/get properties of the view

我的当前这样做的方法是：

My current approach to doing this is:

1. 覆盖 - （id）initWithFrame：

-(id)initWithFrame:(CGRect)frame {
    self = [[[NSBundle mainBundle] loadNibNamed:NSStringFromClass([self class])
                                          owner:self
                                        options:nil] objectAtIndex:0];
    self.frame = frame;
    return self;
}

使用以编程方式实例化 - （id）我的视图控制器中的initWithFrame：

MyCustomView *myCustomView = [[MyCustomView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
[self.view insertSubview:myCustomView atIndex:0];

此工作正常（尽管从不调用 [super init] 并且只是使用加载的nib的内容设置对象似乎有点怀疑 - 这里有建议也可以正常工作）。但是，我希望能够从故事板中实例化视图。所以我可以：

This works fine (although never calling [super init] and simply setting the object using the contents of the loaded nib seems a bit suspect – there is advice here to add a subview in this case which also works fine). However, I'd like to be able to instantiate the view from the storyboard also. So I can:

1. 在故事板中的父视图上放置 UIView / li>
   
2. 将自定义类设置为 MyCustomView



3. 覆盖 - （id）initWithCoder： - 我见过的代码最常适用于以下模式：

1. Place a UIView on a parent view in the storyboard
2. Set its custom class to MyCustomView

3. Override -(id)initWithCoder: – the code I've seen the most often fits a pattern such as the following:

-(id)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        [self initializeSubviews];
    }
    return self;
}

-(id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self initializeSubviews];
    }
    return self;
}

-(void)initializeSubviews {
    typeof(view) view = [[[NSBundle mainBundle]
                         loadNibNamed:NSStringFromClass([self class])
                                owner:self
                              options:nil] objectAtIndex:0];
    [self addSubview:view];
}

当然，这个不起作用，因为我是否使用上面的方法，或者我是否以编程方式实例化，在输入 - （id）initWithCoder： > - （void）initializeSubviews 并从文件中加载nib。

Of course, this doesn't work, as whether I use the approach above, or whether I instantiate programatically, both end up recursively calling -(id)initWithCoder: upon entering -(void)initializeSubviews and loading the nib from file.

其他一些SO问题涉及此问题，例如，，和。但是，没有给出令人满意的答案解决问题：

Several other SO questions deal with this such as here, here, here and here. However, none of the answers given satisfactorily fixes the problem:

• 一个常见的建议似乎是将整个类嵌入到UIViewController中，在那里加载nib，但这对我来说似乎不是最理想的，因为它需要添加另一个文件作为包装器

任何人都可以给出建议如何解决这个问题，并在自定义 UIView 中获得工作网点，并且最小化/没有瘦控制器包装？或者是否有另一种更清洁的方法来处理最少的样板代码？

Could anyone give advice on how to resolve this problem, and get working outlets in a custom UIView with minimum fuss/no thin controller wrapper? Or is there an alternative, cleaner way of doing things with minimum boilerplate code?

推荐答案

您的问题是调用 loadNibNamed：来自（后代） initWithCoder：。 loadNibNamed：在内部调用 initWithCoder：。如果你想覆盖storyboard编码器，并且总是加载你的xib实现，我建议采用以下技术。向视图类添加属性，并在xib文件中将其设置为预定值（在用户定义的运行时属性中）。现在，在调用 [super initWithCoder：aDecoder]; 之后，检查属性的值。如果是预定值，请不要调用 [self initializeSubviews]; 。

Your problem is calling loadNibNamed: from (a descendant of) initWithCoder:. loadNibNamed: internally calls initWithCoder:. If you want to override the storyboard coder, and always load your xib implementation, I suggest the following technique. Add a property to your view class, and in the xib file, set it to a predetermined value (in User Defined Runtime Attributes). Now, after calling [super initWithCoder:aDecoder]; check the value of the property. If it is the predetermined value, do not call [self initializeSubviews];.

所以，像这样：

-(instancetype)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];

    if (self && self._xibProperty != 666)
    {
        //We are in the storyboard code path. Initialize from the xib.
        self = [self initializeSubviews];

        //Here, you can load properties that you wish to expose to the user to set in a storyboard; e.g.:
        //self.backgroundColor = [aDecoder decodeObjectOfClass:[UIColor class] forKey:@"backgroundColor"];
    }

    return self;
}

-(instancetype)initializeSubviews {
    id view =   [[[NSBundle mainBundle] loadNibNamed:NSStringFromClass([self class]) owner:self options:nil] firstObject];

    return view;
}

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