Question

我有这样的事情：

interface ISome {
    myValue: number | string;
    // some more members
}

我有一个函数可以接受ISome myValue是一个数字的function (some: ISome): number { // I accept only ISome with myValue type number return some.myValue + 3; }，并使用它：

some.myValue

typescript编译器按预期抱怨，因为function (some: ISome): number { // I could use a guard if (typeof some.myValue === "number") { return some.myValue + 3; } }是数字或字符串。当然我可以使用联合类型来检查：

  @Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    line = BitmapFactory.decodeResource(getContext().getResources(), R.drawable.line);
    sun = BitmapFactory.decodeResource(getContext().getResources(), R.drawable.circle);

    line = Bitmap.createBitmap(line, 0, 0, line.getWidth(), line.getHeight());



    canvas.drawBitmap(line, 0, 0, null);
    canvas.drawBitmap(sun, 0,0, null);


    Log.d("BITMAP","WIDTH:"+line.getWidth()+" HEIGHT:"+line.getHeight());


    pixelAmount = new int[line.getHeight()*line.getRowBytes()];

    line.getPixels(pixelAmount,0,line.getWidth(),0,0,line.getWidth()-1,line.getHeight()-1);

    Log.d("Line", "Pixel: " + pixelAmount.length + " Index" + 0);
    Log.d("Line", "Pixel: " + pixelAmount[10] + " Index" + 0);
    Log.d("Line", "Pixel: " + pixelAmount[100] + " Index" + 0);
    Log.d("Line", "Pixel: " + pixelAmount[56] + " Index" + 0);
    Log.d("Line", "Pixel: " + pixelAmount[76] + " Index" + 0);


    }
}

但这不是我想要的，因为我经常需要这样做。

Answer 1

您可以使用交集类型覆盖union类型，并在那里指定myValue的类型：

function someFunction(some: ISome & {  
    myValue: number
}): number {
    return some.myValue + 3; // No error
}

在typescript中指定union类型

1 个答案: