Question

我有一个NSTableView，可以用来对列进行排序。字符串，整数和日期列似乎工作正常，但十进制列却导致崩溃，这让我无所适从。

这是数据结构：

class LearningStruct : NSObject, Decodable {
    @objc var ID : Int
    @objc var Text : String
    @objc var Description : String
    @objc var CreationDate : Date
    @objc var UpdateDateTime : Date?
    @objc var ValueX: Decimal
    @objc var IsTrue : Bool
}

（请注意，使用@objc和NSObject，显然Swift无法原生处理排序所需的键值编码）

我创建一些测试JSON数据：

let learningJSON = "{\"Items\": [{\"ID\": 1, \"Text\": \"Item 1 text\", \"Description\": \"This is item 1 description\", \"CreationDate\": \"02/17/2019\", \"ValueX\": 123.45, \"UpdateDate\": \"02/17/2019\", \"IsTrue\": true}, {\"ID\": 2, \"Text\": \"Item 2 text\", \"Description\": \"This is item 2 description\", \"CreationDate\": \"02/14/2019\", \"ValueX\": 789.01, \"UpdateDate\": \"02/14/2019\", \"IsTrue\": false}]}"
internal var learningItems = [LearningStruct]()

然后我使用解码器填充数组：

            let decoder = JSONDecoder()
            let dateformatter = DateFormatter()
            dateformatter.dateFormat = "MM/dd/yyyy" // "MM/dd/yyyy'T'HH:mm:ss"
            decoder.dateDecodingStrategy = .formatted(dateformatter)
            decoder.keyDecodingStrategy = .convertFromSnakeCase
            let learningData = try decoder.decode(LearningItems.self, from: learningJSON.data(using: .utf8)!) as LearningItems
            learningItems = learningData.Items

NSTableColumns将其标识符设置为情节提要中的属性名称，以便于映射。

           for prop in properties {
                let colindex = learningTableView.column(withIdentifier: NSUserInterfaceItemIdentifier.init(prop)) // Get the column index number for that property key
                if (colindex >= 0) { // If the column exists
                    let descriptorID = NSSortDescriptor(key: prop, ascending: true)
                    learningTableView.tableColumns[colindex].sortDescriptorPrototype = descriptorID
                }
            }

这是排序逻辑：

/// Sorting logic
    func tableView(_ tableView: NSTableView, sortDescriptorsDidChange oldDescriptors: [NSSortDescriptor]) {

        print("--- Sorting logic begin ---")

        // Debug print the sorters
        for col in learningTableView.tableColumns {

            if col.sortDescriptorPrototype != nil {
                let sorter = col.sortDescriptorPrototype!.key!
                let direction = col.sortDescriptorPrototype!.ascending
                print("Column \(col.identifier.rawValue): sort descriptor: \(sorter), is ascending: \(direction)")
            } else {
                print("Column \(col.identifier.rawValue): no sort descriptor")
            }
        }

        print("+++ Sort descriptors list")
        let learningItemsMutable = NSMutableArray(array: learningItems)
        let sorters = tableView.sortDescriptors
        for sortdesc in sorters {
            print("Sort descriptor: \(sortdesc.key!)")
        }
        print("Sorting...")
        learningItemsMutable.sort(using: sorters)
        learningItems = learningItemsMutable as! [LearningStruct]
        tableView.reloadData()
        print("--- Sorting logic end ---")
    }

运行代码时，单击列直到到达“ ValueX”列，它对所有内容进行完美排序。下面的示例是我按顺序单击每列，以“ Value X”结尾。当我单击该按钮时，我得到的例外情况并不能真正帮助我...任何人都可以帮助您吗？

--- Sorting logic begin ---
Column ID: sort descriptor: ID, is ascending: true
Column Text: sort descriptor: Text, is ascending: true
Column Description: sort descriptor: Description, is ascending: true
Column CreationDate: sort descriptor: CreationDate, is ascending: true
Column ValueX: sort descriptor: ValueX, is ascending: true
Column IsTrue: sort descriptor: IsTrue, is ascending: true
+++ Sort descriptors list
Sort descriptor: ValueX
Sort descriptor: CreationDate
Sort descriptor: Description
Sort descriptor: Text
Sort descriptor: ID
Sorting...
2019-02-22 12:29:27.093825+0000 NSTableView Learning[8571:1649436] [General] -[NSInvocation getArgument:atIndex:]: struct with unknown contents found while getting argument at index -1
2019-02-22 12:29:27.095961+0000 NSTableView Learning[8571:1649436] [General] (
    0   CoreFoundation                      0x00007fff4aecaded __exceptionPreprocess + 256
    1   libobjc.A.dylib                     0x00007fff76f96720 objc_exception_throw + 48
    2   CoreFoundation                      0x00007fff4ae22af3 -[NSInvocation getArgument:atIndex:] + 473
    3   Foundation                          0x00007fff4d251a85 _NSGetValueWithMethod + 174
    4   Foundation                          0x00007fff4d184494 -[NSObject(NSKeyValueCoding) valueForKey:] + 284
    5   Foundation                          0x00007fff4d193d68 _sortedObjectsUsingDescriptors + 389
    6   Foundation                          0x00007fff4d1be3c9 -[NSMutableArray(NSKeyValueSorting) sortUsingDescriptors:] + 497
    7   NSTableView Learning                0x000000010000d3c9 $S20NSTableView_Learning0cB10ControllerC05tableB0_24sortDescriptorsDidChangeySo0aB0C_SaySo16NSSortDescriptorCGtF + 5289
    8   NSTableView Learning                0x000000010000dacf $S20NSTableView_Learning0cB10ControllerC05tableB0_24sortDescriptorsDidChangeySo0aB0C_SaySo16NSSortDescriptorCGtFTo + 111
    9   AppKit                              0x00007fff48b9e388 -[NSTableView _sendDataSourceSortDescriptorsDidChange:] + 82
    10  AppKit                              0x00007fff4862275a -[NSTableView setSortDescriptors:] + 327
    11  AppKit                              0x00007fff48b9e5ca -[NSTableView _changeSortDescriptorsForClickOnColumn:] + 542
    12  AppKit                              0x00007fff48b81d73 -[NSTableHeaderView _trackAndModifySelectionWithEvent:onColumn:stopOnReorderGesture:] + 1000
    13  AppKit                              0x00007fff48b84eeb -[NSTableHeaderView mouseDown:] + 596
    14  AppKit                              0x00007fff4859f1eb -[NSWindow(NSEventRouting) _handleMouseDownEvent:isDelayedEvent:] + 5668
    15  AppKit                              0x00007fff484d3223 -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:] + 2319
    16  AppKit                              0x00007fff484d26c9 -[NSWindow(NSEventRouting) sendEvent:] + 481
    17  AppKit                              0x00007fff4836f954 -[NSApplication(NSEvent) sendEvent:] + 336
    18  AppKit                              0x00007fff4835d19d -[NSApplication run] + 755
    19  AppKit                              0x00007fff4834c8a3 NSApplicationMain + 780
    20  NSTableView Learning                0x000000010001085d main + 13
    21  libdyld.dylib                       0x00007fff78064ed9 start + 1
    22  ???                                 0x0000000000000003 0x0 + 3
)

Answer 1

Objective-C Decimal中使用的类型NSDecimal不在受支持的键值编码类型列表中。 KVC documentation

typedef struct {
    signed   int _exponent:8;
    unsigned int _length:4;     // length == 0 && isNegative -> NaN
    unsigned int _isNegative:1;
    unsigned int _isCompact:1;
    unsigned int _reserved:18;
    unsigned short _mantissa[NSDecimalMaxSize];
} NSDecimal;

NSDecimal使用的位字段是关键问题。

每次尝试使之工作（这应该是可能的）都是开箱即用的。

Answer 2

Decimal与NSDecimalNumber的桥接方式可能存在一些问题

尝试在NSDecimalNumber类中使用LearningStruct来查看崩溃是否仍然存在。

或者创建一个新的只读属性，并将其用于排序：

class LearningStruct: NSObject, Decodable {
    @objc var ID: Int
    @objc var Text: String
    @objc var Description: String
    @objc var CreationDate: Date
    @objc var UpdateDateTime: Date?
    @objc var ValueX: Decimal
    @objc var IsTrue: Bool

    @objc var ValueXNumber: NSDecimalNumber {
        return ValueX as NSDecimalNumber
    }
}

相关说明：实例变量通常在Swift中以小写的首字母命名。并且@objc是必需的，因为NSSortDescriptor是一个Objective-C类，否则它将看不到Swift类的属性。

NSTableView排序十进制列导致异常

2 个答案: