[英]How do I override GetHashCode() without any numbers as fields?
所有显示如何重写Equals(object)
和GetHashCode()
使用数字字段来实现GetHashCode()
方法:
实施平等方法
Equals和GetHashCode的最佳策略是什么?
当覆盖Equals方法时,覆盖GetHashCode为什么很重要?
但是,在我的课堂上,我没有任何数字字段。 它是树中的一个节点,引用其父节点,子节点和一个接口作为数据:
public class Node
{
private IInterface myInterface;
private Node parent;
private List<Node> children = new List<Node>();
public override bool Equals(object obj)
{
if (obj == null || GetType() != obj.GetType())
{
return false;
}
var node = (Node)obj;
return myInterface == node.myInterface;
}
public override int GetHashCode()
{
???
}
}
我应该用什么设置哈希码?
据Equals
实现中,两个Node
小号实例是相等的,当且仅当它们myInterface
是平等的:
public override bool Equals(object obj)
{
if (obj == null || GetType() != obj.GetType())
{
return false;
}
var node = (Node)obj;
// instances are equal if and only if myInterface's are equal
return myInterface == node.myInterface;
}
这就是为什么myInterface
是GetHashCode
的唯一来源的原因:
public override int GetHashCode()
{
return null == myInterface ? 0 : myInterface.GetHashCode();
}
PS ( 编辑 ,感谢Kris Vandermotten)通常,比较比较可能耗时的myInterface
的时间/资源,在Equals
实现中检查ReferenceEquals
是一个好习惯:
public override bool Equals(object obj) {
// Easy tests:
// 1. If "this" and "obj" are in fact just the same reference?
// 2. Since `Node` (or Equals) is not sealed, the safiest is to check types
if (object.ReferenceEquals(this, obj))
return true;
else if (null == obj || other.GetType() != GetType())
return false;
// Potentially time/resource cosuming (we don't know IInterface implementation)
return ((Node) obj).myInterface == myInterface;
}
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