Obj-C在单独的文件中委托实现

Question

我正在尝试清理我的代码。 我的ViewController中有3个pickerView，我希望在单独的文件中实现委托。

id imp = [[HourPickerImplementation alloc] init];
self.hourPicker.dataSource = imp;
self.hourPicker.delegate = imp;

HourPickerImplementation.h ：

@interface HourPickerImplementation : NSObject <UIPickerViewDataSource, UIPickerViewDelegate>

@end

HourPickerImplementation.m ：

@implementation HourPickerImplementation {
  NSMutableArray *_pickerData;
}

- (id)init {
  _pickerData = [[NSMutableArray alloc] initWithCapacity:25];
  for (int i = 0; i < 25; i++) {
    [_pickerData addObject:[NSString stringWithFormat:@"%d H.", i]];
  }
  return self;
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
  return 1;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView
numberOfRowsInComponent:(NSInteger)component {
  return _pickerData.count;
}

- (UIView *)pickerView:(UIPickerView *)pickerView
            viewForRow:(NSInteger)row
          forComponent:(NSInteger)component
           reusingView:(UIView *)view {
  UIImage *img = [UIImage imageNamed:@"icon_lock.png"];
  UIImageView *temp = [[UIImageView alloc] initWithImage:img];
  temp.frame = CGRectMake(51, 20, 20, 20);

  UILabel *channelLabel =
      [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 50, 60)];
  channelLabel.text =
      [NSString stringWithFormat:@"%@", [_pickerData objectAtIndex:row]];
  channelLabel.textColor = [UIColor whiteColor];
  channelLabel.backgroundColor = [UIColor clearColor];

  UIView *tmpView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 110, 60)];
  [tmpView insertSubview:temp atIndex:0];
  [tmpView insertSubview:channelLabel atIndex:1];

  return tmpView;
}

不幸的是它给了我这个错误：

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x170099c80 V:[UIImageView:0x12751a110(55)]>

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.
2015-08-26 10:30:30.489 bollywood[675:103276] 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:0x17009a540 V:[UIImageView:0x12751c480(55)]>",
    "<NSLayoutConstraint:0x17009a590 V:[UIImageView:0x12751c5c0(50)]>",
    "<NSLayoutConstraint:0x17009a810 V:[UIImageView:0x12751c480]-(12)-[UIImageView:0x12751c5c0]>",
    "<NSLayoutConstraint:0x17009a900 UITableViewCellContentView:0x12751bcd0.bottomMargin == UIImageView:0x12751c5c0.bottom>",
    "<NSLayoutConstraint:0x17009aa40 UIImageView:0x12751c480.top == UITableViewCellContentView:0x12751bcd0.topMargin + 12>",
    "<NSLayoutConstraint:0x1740961c0 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x12751bcd0(139)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x17009a540 V:[UIImageView:0x12751c480(55)]>

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. 

我究竟做错了什么？ 它在一个文件中工作，但看起来很糟糕。

Answer 1

该错误暗示您的单元格中的约束无法满足，因为它们的组要求布局无法实现。

查看输出，以下行可能是问题：

<NSLayoutConstraint:0x1740961c0 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x12751bcd0(139)]>

此约束可能由选择器视图根据您从rowForHeightForComponent返回的内容rowForHeightForComponent 。 这个高度似乎是139pts。

首先检查您的委托方法是否实际被调用。 你说你拆分文件了。 猜测是系统将其设置为139，因为它已经移动，因为它没有看到新的代理代码。

您的其他约束似乎是2个高度为55和50的图像，间隔为12和12的上边距。约束中的总固定高度为117.我注意到您还使用了布局到边距。 如果这不是您的意图，请将其更改为与实际顶部相对应。

因此，您的问题是单元格内容希望以固定的大小/间距打包，但在设置为139pts时仍无法与顶部和底部对齐。

我的建议是检查你返回的行高的计算。

您可以通过将底部图像的底部约束和正在对齐的内容视图的底部更改为从内容视图底部固定图像底部> = 0的约束来解决约束问题。 通过使此固定> = 0，约束将不再失败。 您将看到的是底部的间隙，您现在可以应对代码中返回的高度之间的不匹配。

Answer 2

解：

问题在这里：

- (void)viewDidLoad {
  [super viewDidLoad];

  id imp = [[HourPickerImplementation alloc] init];
  self.hourPicker.dataSource = imp;
  self.hourPicker.delegate = imp;
}

完成该方法后，我的代表被解除分配。 我不得不将我的局部变量更改为全局变量。

- (void)viewDidLoad {
  [super viewDidLoad];

  _imp = [[HourPickerImplementation alloc] init];
  self.hourPicker.dataSource = _imp;
  self.hourPicker.delegate = _imp;
}

现在它的工作（感谢@Rory McKinnel）