假设我有一个类，它有许多实例变量，.我想重载==运算符(和hashCode)，以便在映射中使用实例作为键.
class Foo {
int a;
int b;
SomeClass c;
SomeOtherClass d;
// etc.
bool operator==(Foo other) {
// Long calculation involving a, b, c, d etc.
}
}
比较计算可能很昂贵，所以在进行计算之前，我想判断other是否与this相同.
如何调用Object类提供的==运算符来执行此操作？
您正在寻找"identical"，它将判断两个实例是否相同.
identical(this, other);
一个更详细的例子？
class Person {
String ssn;
String name;
Person(this.ssn, this.name);
// Define that two persons are equal if their SSNs are equal
bool operator ==(Person other) {
return (other.ssn == ssn);
}
}
main() {
var bob = new Person('111', 'Bob');
var robert = new Person('111', 'Robert');
print(bob == robert); // true
print(identical(bob, robert)); // false, because these are two different instances
}