ios - 在单元测试 UIDatePicker 时获取运行时异常([UIPickerColumnView isDragging :] unrecognized selector)

Question

我创建了一个带有 UIDatePicker socket 的 UIViewController，相应的 nib 文件，并在界面生成器中正确设置了 socket 。

我正在尝试运行以下单元测试(使用 OCHamcrest 匹配器库)。

- (void)test___datePicker___shouldBeConnected
{
  [sut view];
  assertThat(sut.datePicker, is(notNilValue()));
}

sut(“被测系统”)是被单元测试的 View Controller 。

但是，我不断收到此运行时异常:

[UIPickerColumnView isDragging]: unrecognized selector sent to instance 0x10dcdcc70

UIPickerColumnView 不是我创建的类(它似乎是 UIKit 中使用的非公共(public)类)。

我试过从 ni​​b 中删除 UIDatePicker 并以编程方式创建它:

- (void)viewDidLoad
{
  [super viewDidLoad];

  UIDatePicker *datePicker = [[UIDatePicker alloc] init];
  [datePicker setDate:[NSDate date]];
  [datePicker addTarget:self action:@selector(dateChanged:)
   forControlEvents:UIControlEventValueChanged];
  [self.view addSubview:datePicker];
}

但是，同样的异常发生。

异常断点，错误线程如下:

#0  0x0000000100857973 in objc_exception_throw ()
#1  0x0000000100c8065d in -[NSObject(NSObject) doesNotRecognizeSelector:] ()
#2  0x0000000100be0d8d in ___forwarding___ ()
#3  0x0000000100be0938 in __forwarding_prep_0___ ()
#4  0x00000001066c5b6e in -[UIPickerView _sendSelectionChangedFromTable:notify:] ()
#5  0x00000001066c5fec in -[UIPickerView _selectRow:inComponent:animated:notify:] ()
#6  0x0000000106c7bac7 in -[_UIDatePickerView _selectRow:inComponent:animated:notify:] ()
#7  0x0000000106c81c3f in -[_UIDatePickerMode loadDate:animated:] ()
#8  0x0000000106c85456 in -[_UIDatePickerMode_DateAndTime loadDate:animated:] ()
#9  0x0000000106c7ba8b in -[_UIDatePickerView _loadDate:animated:] ()
#10 0x0000000106c7b26b in -[_UIDatePickerView _setDate:animated:forced:] ()
#11 0x0000000106911c0e in -[UIDatePicker initWithCoder:] ()
#12 0x0000000106a6a794 in UINibDecoderDecodeObjectForValue ()
#13 0x0000000106a6a4df in -[UINibDecoder decodeObjectForKey:] ()
#14 0x000000010692e198 in -[UIRuntimeConnection initWithCoder:] ()
#15 0x0000000106a6a794 in UINibDecoderDecodeObjectForValue ()
#16 0x0000000106a6a95c in UINibDecoderDecodeObjectForValue ()
#17 0x0000000106a6a4df in -[UINibDecoder decodeObjectForKey:] ()
#18 0x000000010692d7b6 in -[UINib instantiateWithOwner:options:] ()
#19 0x00000001067c7b0c in -[UIViewController _loadViewFromNibNamed:bundle:] ()
#20 0x00000001067c8149 in -[UIViewController loadView] ()
#21 0x00000001067c83b7 in -[UIViewController loadViewIfRequired] ()
#22 0x00000001067c8777 in -[UIViewController view] ()
#23 0x0000000102e01c86 in -[AODateTimeDetailViewControllerTests test___datePicker___ShouldBeConnected] at /Users/Anthony/Documents/AORepos/AOReportControllers/AOReportControllersTests/AODateTimeDetailViewControllerTests.m:43
#24 0x0000000100be4f1c in __invoking___ ()
#25 0x0000000100be4dc4 in -[NSInvocation invoke] ()
#26 0x0000000102cb9c40 in -[XCTestCase invokeTest] ()
#27 0x0000000102cb9d2c in -[XCTestCase performTest:] ()
#28 0x0000000102cbaa75 in -[XCTest run] ()
#29 0x0000000102cb94df in -[XCTestSuite performTest:] ()
#30 0x0000000102cbaa75 in -[XCTest run] ()
#31 0x0000000102cb94df in -[XCTestSuite performTest:] ()
#32 0x0000000102cbaa75 in -[XCTest run] ()
#33 0x0000000102cb94df in -[XCTestSuite performTest:] ()
#34 0x0000000102cbaa75 in -[XCTest run] ()
#35 0x0000000102cbc1b4 in +[XCTestProbe runTests:] ()
#36 0x00000001000012e1 in ___lldb_unnamed_function9$$xctest ()
#37 0x0000000100001521 in ___lldb_unnamed_function11$$xctest ()
#38 0x0000000100001017 in ___lldb_unnamed_function2$$xctest ()

如何防止在单元测试 UIDatePicker 时抛出此异常？

Answer 1

我可以在单元测试时使用 UIDatePicker 确认此行为，似乎其他 iOS 开发人员也遇到此问题 ( https://discussions.apple.com/message/25373309)。

不幸的是，这似乎是 iOS 7 SKD (Xcode 5.1) 中的错误。但是，它似乎已在 iOS 8 SDK (Xcode 6 beta 1) 中修复。

如果您访问 UIViewController 的 view 属性并且它包含一个 UIDatePicker，则会抛出此异常，这是您通常会导致view 及其在单元测试期间设置的导出。

这是我用来解决它的解决方案:

@interface YourViewControllerTests
@end

@implementation YourViewControllerTests
{
  YourViewController *sut;
  UIDatePicker *datePicker;
}

- (void)setUp
{
  [super setUp];

  sut = [[YourViewController alloc] initWithNibName:@"YourViewController" bundle:[NSBundle bundleForClass:[self class]]];
  [self givenViewSetup];
}

- (void)givenViewSetup
{
  @try {
    [sut view];
  }
  @catch (NSException *exception) {
    // ignore the exception
  }
  @finally {
    datePicker = [[UIDatePicker alloc] init];
    sut.datePicker = datePicker;
  }
}

- (void)test___datePicker___shouldBeConnected
{
  assertThat(sut.datePicker, is(notNilValue()));
}

@end

虽然您的 UIDatePicker socket 现在没有经过技术单元测试，但至少您可以继续对 View Controller 进行其余测试。

当然，请务必在切换到 Xcode 6 后立即放弃这种 try-catch 废话! :]