IComparable的和IComparer的区别 [英] difference between IComparable and IComparer

问题描述

可能重复：结果
的何时使用IComparable的< T>与的IComparer< T>

是IComparable接口和IComparer的接口之间有什么区别？是否有必要用的Array.Sort（）方法。

what is the difference between IComparable and IComparer Interfaces? Is it necessary to use this interface always with Array.Sort() method

推荐答案

一直使用这个接口。顾名思义， IComparable的< T> 读出的我可比的。 IComparable的< T> 为 T 允许定义，当你的比较的的的当前实例的同类型的另一个实例。 的IComparer< T> 读出的我是一个比较器，我比较的。 的IComparer< T> 用于 T 中的任何两个实例比较，典型的外<$的实例范围C $ C> T 。

As the name suggests, IComparable<T> reads out I'm comparable. IComparable<T> when defined for T lets you compare the current instance with another instance of same type. IComparer<T> reads out I'm a comparer, I compare. IComparer<T> is used to compare any two instances of T, typically outside the scope of the instances of T.

至于他们是什么可以在第一次混乱。从定义，它应该清楚，因此 IComparable的< T> （在类中定义的 T 本身）应该是事实上的标准来进行排序提供的逻辑。默认排序在列表< T> 等依赖于此。实施的IComparer< T>在 T 不利于正规排序。随后，对于实施 IComparable的<价值不大; T> 比 T 以外的任何其他类。这样的：

As to what they are for can be confusing at first. From the definition it should be clear that hence IComparable<T> (defined in the class T itself) should be the de facto standard to provide the logic for sorting. The default Sort on List<T> etc relies on this. Implementing IComparer<T> on T doesn't help regular sorting. Subsequently, there is little value for implementing IComparable<T> on any other class other than T. This:

class MyClass : IComparable<T>

很少是有道理的。

rarely makes sense.

在该另一方面

class T : IComparable<T>
{
    public int CompareTo(T other)
    {
        //....
    }
}

时应该怎么做。

的IComparer< T> 当你需要基于自定义顺序排序，而不是作为一个一般的规则是有用的。例如，在某些时候一类人您可能需要排序根据他们的年龄的人。在这种情况下，你可以这样做：

IComparer<T> can be useful when you require sorting based on a custom order, but not as a general rule. For instance, in a class of Person at some point you might require to Sort people based on their age. In that case you can do:

class Person
{
    public int Age;
}

class AgeComparer : IComparer<Person>
{
    public int Compare(Person x, Person y)
    {
        return x.Age - y.Age;
    }
}

现在的 AgeComparer 有助于排序依据年龄列表。

Now the AgeComparer helps in sorting a list based on Age.

var people = new Person[] { new Person { age = 23 }, new Person(){ age = 22 } };
people.Sort(p, new AgeComparer()); //person with age 22 comes first now.

同样的IComparer< C $ C> T 没有意义。

class Person : IComparer<Person>

true此工作，但并不好看眼睛和失败的逻辑。

True this works, but doesn't look good to eyes and defeats logic.

通常你需要的是 IComparable的< T> 。此外理想情况下你只能有一个 IComparable的< T> 而多个的IComparer< T> 可根据不同的标准。

Usually what you need is IComparable<T>. Also ideally you can have only one IComparable<T> while multiple IComparer<T> is possible based on different criteria.

的IComparer< T> 和 IComparable的< T> 是完全类似于的IEqualityComparer< T> 和 IEquatable< T> 这是用于测试的平等而不是比较/排序;一个良好的线程 的，我写的完全一样的答案： ）

The IComparer<T> and IComparable<T> are exactly analogous to IEqualityComparer<T> and IEquatable<T> which are used for testing equality rather than comparing/sorting; a good thread here where I wrote the exact same answer :)

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