When working with optional values, you can write? Before operations like methods, properties, and subscripting.

使用可选的值时，你可以写吗？手术前像方法，属性，和下标。

youdao

When working with optional values, you can write? Before operations like methods, properties, and subscripting.

使用可选的值时，你可以写吗？手术前像方法，属性，和下标。

youdao