Question

我需要声明一个泛型函数，该函数返回一个泛型单元格，为此，我实现了以下操作，

private func getVisibleCellAs<Cell>() -> Cell? {
    if let visibleCell = self.registrationTableView.visibleCells.first, let expectedCell = visibleCell as? Cell {
        return expectedCell
    }
    return nil
}

现在，我称其为

if let personalDetailsCell = self.getVisibleCellAs<PersonalDetailsTableViewCell>() {
            return personalDetailsCell.validatePersonalDetails()
}

但是，它显示为（在函数调用中）错误

Cannot explicitly specialize a generic function

如果尝试致电。

Answer 1

Swift不允许您手动指定要传递给函数的通用参数，而是必须可以从上下文计算得出。您在这里至少有三个选择：

声明变量类型：

if let personalDetailsCell: PersonalDetailsTableViewCell = self.getVisibleCellAs() { ... }

广播结果：

if let personalDetailsCell = self.getVisibleCellAs() as PersonalDetailsTableViewCell { ... }

如果将结果传递给另一个函数，则编译器应该能够推断出：

func configure(personCell cell: PersonalDetailsTableViewCell) { ... }
// later on
configure(personCell: self.getVisibleCellAs())

Answer 2

您不能明确地专门化这样的泛型函数。

但是您可以这样做：

Dim i As Long
Dim LastRow As Long

LastRow = Cells(Rows.Count, rowtofilter).End(xlUp).Row

'Search for merged cells and not "string1" in column2 and not "string2" in column4, replace text
For i = rowtofilter To LastRow
    If Range(ColumnLetter1 & i).MergeArea.Cells.Count > 1 And Range(ColumnLetter2 & i) <> "string1" And Range(ColumnLetter4 & i) <> "string2" Then
        Range(ColumnLetter3 & i).Value = "Merged Cells"
    End If
Next i

'Search for merged cells and not "string1" in column2 and not "string2" in column4, delete rows
i = LastRow - rowtofilter
Do While i > (rowtofilter - 1)
    If Range(ColumnLetter1 & i).Value = 0 And Range(ColumnLetter2 & i) <> "string1" And Range(ColumnLetter4 & i) <> "string2" Then
        Range(ColumnLetter1 & i).EntireRow.Delete
    End If
    i = i - 1
Loop

泛型函数声明引发错误

2 个答案: