在swift VC中以编程方式在代码中指定约束时，布局属性的配对无效

Question

我遵循示例中使用的模式：

https://github.com/lucasderraugh/AppleProg-Cocoa-Tutorials/blob/master/Lesson%2066/Lesson%2066/AppDelegate.swift

我的VC (NSViewController的子类)如下所示：

import Cocoa

class SecondViewController: NSViewController {

    var leftView = ColorView()
    var rightView = ColorView()

    @IBOutlet weak var nameTextField: NSTextField!
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do view setup here.


    }

    override func viewDidAppear() {

        leftView.translatesAutoresizingMaskIntoConstraints = false
        rightView.translatesAutoresizingMaskIntoConstraints = false



        let leftConstraints:[NSLayoutConstraint] = [

            leftView.widthAnchor.constraintEqualToAnchor(self.view.topAnchor),
            leftView.leftAnchor.constraintEqualToAnchor(self.view.leftAnchor),
            leftView.widthAnchor.constraintEqualToConstant(100),
            leftView.heightAnchor.constraintEqualToConstant(100)

        ]

        self.view.addSubview(leftView)

        NSLayoutConstraint.activateConstraints(leftConstraints)

    }

    override func prepareForSegue(segue: NSStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "SecondToFourthSegue" {
            (segue.destinationController as! NSViewController).representedObject = nameTextField.stringValue
        }
    }


}

但我在运行时得到以下错误：

布局属性的配对无效

完整堆栈跟踪：

2016-04-26 00:54:06.402 Hyperterm[19046:1591173] An uncaught exception was raised
2016-04-26 00:54:06.403 Hyperterm[19046:1591173] *** +[NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:]: Invalid pairing of layout attributes
2016-04-26 00:54:06.403 Hyperterm[19046:1591173] (
    0   CoreFoundation                      0x00007fff89cf94f2 __exceptionPreprocess + 178
    1   libobjc.A.dylib                     0x00007fff8b89b73c objc_exception_throw + 48
    2   CoreFoundation                      0x00007fff89d604bd +[NSException raise:format:] + 205
    3   Foundation                          0x00007fff8d717f92 VerifyConstraintArguments + 356
    4   Foundation                          0x00007fff8d717c16 +[NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:] + 295
    5   Foundation                          0x00007fff8d71d410 -[NSLayoutAnchor constraintEqualToAnchor:multiplier:constant:] + 149
    6   Foundation                          0x00007fff8d71e87f -[NSLayoutDimension constraintEqualToAnchor:multiplier:constant:] + 39
    7   Hyperterm                           0x000000010001bee1 _TFC9Hyperterm20SecondViewController13viewDidAppearfT_T_ + 385
    8   Hyperterm                           0x000000010001c4b2 _TToFC9Hyperterm20SecondViewController13viewDidAppearfT_T_ + 34
    9   libdispatch.dylib                   0x0000000100607070 _dispatch_call_block_and_release + 12
    10  libdispatch.dylib                   0x00000001005f9cc5 _dispatch_client_callout + 8
    11  libdispatch.dylib                   0x00000001006116ae _dispatch_main_queue_callback_4CF + 2845
    12  CoreFoundation                      0x00007fff89cae9e9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
    13  CoreFoundation                      0x00007fff89c6d8dd __CFRunLoopRun + 1949
    14  CoreFoundation                      0x00007fff89c6ced8 CFRunLoopRunSpecific + 296
    15  HIToolbox                           0x00007fff949a7935 RunCurrentEventLoopInMode + 235
    16  HIToolbox                           0x00007fff949a776f ReceiveNextEventCommon + 432
    17  HIToolbox                           0x00007fff949a75af _BlockUntilNextEventMatchingListInModeWithFilter + 71
    18  AppKit                              0x00007fff878aeefa _DPSNextEvent + 1067
    19  AppKit                              0x00007fff878ae32a -[NSApplication _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 454
    20  AppKit                              0x00007fff878a2e84 -[NSApplication run] + 682
    21  AppKit                              0x00007fff8786c46c NSApplicationMain + 1176
    22  Hyperterm                           0x000000010001b724 main + 84
    23  libdyld.dylib                       0x00007fff8fc285ad start + 1
    24  ???                                 0x0000000000000003 0x0 + 3
)
2016-04-26 00:54:06.405 Hyperterm[19046:1591173] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:]: Invalid pairing of layout attributes'
*** First throw call stack:
(
    0   CoreFoundation                      0x00007fff89cf94f2 __exceptionPreprocess + 178
    1   libobjc.A.dylib                     0x00007fff8b89b73c objc_exception_throw + 48
    2   CoreFoundation                      0x00007fff89d604bd +[NSException raise:format:] + 205
    3   Foundation                          0x00007fff8d717f92 VerifyConstraintArguments + 356
    4   Foundation                          0x00007fff8d717c16 +[NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:] + 295
    5   Foundation                          0x00007fff8d71d410 -[NSLayoutAnchor constraintEqualToAnchor:multiplier:constant:] + 149
    6   Foundation                          0x00007fff8d71e87f -[NSLayoutDimension constraintEqualToAnchor:multiplier:constant:] + 39
    7   Hyperterm                           0x000000010001bee1 _TFC9Hyperterm20SecondViewController13viewDidAppearfT_T_ + 385
    8   Hyperterm                           0x000000010001c4b2 _TToFC9Hyperterm20SecondViewController13viewDidAppearfT_T_ + 34
    9   libdispatch.dylib                   0x0000000100607070 _dispatch_call_block_and_release + 12
    10  libdispatch.dylib                   0x00000001005f9cc5 _dispatch_client_callout + 8
    11  libdispatch.dylib                   0x00000001006116ae _dispatch_main_queue_callback_4CF + 2845
    12  CoreFoundation                      0x00007fff89cae9e9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
    13  CoreFoundation                      0x00007fff89c6d8dd __CFRunLoopRun + 1949
    14  CoreFoundation                      0x00007fff89c6ced8 CFRunLoopRunSpecific + 296
    15  HIToolbox                           0x00007fff949a7935 RunCurrentEventLoopInMode + 235
    16  HIToolbox                           0x00007fff949a776f ReceiveNextEventCommon + 432
    17  HIToolbox                           0x00007fff949a75af _BlockUntilNextEventMatchingListInModeWithFilter + 71
    18  AppKit                              0x00007fff878aeefa _DPSNextEvent + 1067
    19  AppKit                              0x00007fff878ae32a -[NSApplication _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 454
    20  AppKit                              0x00007fff878a2e84 -[NSApplication run] + 682
    21  AppKit                              0x00007fff8786c46c NSApplicationMain + 1176
    22  Hyperterm                           0x000000010001b724 main + 84
    23  libdyld.dylib                       0x00007fff8fc285ad start + 1
    24  ???                                 0x0000000000000003 0x0 + 3
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

leftView.widthAnchor不应等于self.view.topAnchor，您可能不会注意到它