The core problem is that Dart makes a semantic distinction between "passednull" and "did not pass a value", but the latter has no first-class representation in the language. Where JS hasundefined, we have nothing. Getting rid ofundefinedis great, but our optional parameter semantics still ha...
例如我们在 Dart 中有一个求和函数,它接收三个参数,最后返回这三个数的和 //求和 int summation(int a, int b, int c) { return a + b + c; } // ··· int total = summation(1, 2, 3); Copy 如果我们想要后面两个参数是选填的,可以使用可选位置参数,只要把这些参数放在方括号中,它们就是...