指定变量类型可以是两个值中的任何一个

Question

如何在stypescript中指定变量可以是Car或Bar类型？

class Car {
  wheels: number;
}

class Bar {
  drinks: number;
}

let foo: Car | Bar;
// now foo has to have the fields of Car AND Bar.
// I would like foo to be of type Car, OR Bar
// foo = { wheels: 4} should not raise an error
// foo = { drinks: 4} should not raise an error

Answer 1

您必须将您的用法包装在Sub SavePicToFile(namefile) Selection.CopyPicture xlScreen, xlBitmap Application.DisplayAlerts = False Set tmp = Charts.Add On Error Resume Next With tmp .SeriesCollection(1).Delete .Width = Selection.Width .Height = Selection.Height .Paste .Export filename:=namefile, Filtername:="jpeg" .Delete End With End Sub foto = Application.ActiveWorkbook.Path & "\Foto" & ".jpeg" ActiveWorkbook.Sheets(1).Range("A1:Z30").Select SavePicToFile (foto) ：

中

instanceof

打字稿需要知道，否则它不会阻止您尝试访问class Car { wheels: number; } class Bar { drinks: number; } let foo: Car | Bar; if (foo instanceof Car) { foo.wheels; } if (foo instanceof Bar) { foo.drinks; } 对象上的wheels，这会使它变得不那么有用。

根据您的示例，分配：Bar似乎没有在typescript playground中抱怨。