C# - 关闭 - 澄清

发布于 2024-08-26 23:20:35 字数 648 浏览 6 评论 0原文

我正在学习 C#。我可以将闭包理解为一个可以采用定义它的环境中的更改的构造吗？

示例：

List<Person> gurus = 
new List<Person>()
                 {
                  new Person{id=1,Name="Jon Skeet"},
                  new Person{id=2,Name="Marc Gravell"},
                  new Person{id=3,Name="Lasse"}
                 };            


void FindPersonByID(int id)
{
  gurus.FindAll(delegate(Person x) { return x.id == id; }); 
}

变量 id 在作用域中声明FindPersonByID() 但我们仍然可以访问匿名函数内的局部变量id（即）delegate(Person x) { return x.id == id; }

(1)我对闭包的理解是否正确？

（2）闭包能给我们带来什么好处？

原文

I am learning C#.Can I mean closure as a construct that can adopt the changes in the environment in which it is defined.

Example :

List<Person> gurus = 
new List<Person>()
                 {
                  new Person{id=1,Name="Jon Skeet"},
                  new Person{id=2,Name="Marc Gravell"},
                  new Person{id=3,Name="Lasse"}
                 };            


void FindPersonByID(int id)
{
  gurus.FindAll(delegate(Person x) { return x.id == id; }); 
}

The variable id is declared in the scope of FindPersonByID() but t we still can access
the local variable id inside the anonymous function (i.e) delegate(Person x) { return x.id == id; }

(1) Is my understanding of closure is correct ?

(2) What are the advantages can we get from closures?

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独行侠 2024-09-02 23:20:35

是的，FindPersonByID 内部的代码通过在 lambda 表达式中使用参数 id 来利用闭包。严格来说，闭包的定义有点复杂，但在基本层面上这是正确的。如果您想了解有关它们如何运作的更多信息，我鼓励您阅读以下文章

闭包的主要优点本质上就是您上面所演示的。它允许您以更自然、直接的方式编写代码，而不必担心如何生成 lambda 表达式的实现细节（通常）

考虑例如在没有闭包的情况下您需要编写多少代码

class Helper {
  private int _id;
  public Helper(int id) { 
    _id = id;
  }
  public bool Filter(Person p) {
    return p.id == _id;
  }
}

void FindPersonsByID(int id) {
  Helper helper = new Helper(id);
  gurus.FindAll(helper.Filter);
}

All这只是为了表达在委托内部使用参数的概念。

Yes the code inside of FindPersonByID is taking advantage of a closure by using the parameter id within the lambda expression. Strictly speaking the definitions of closures are a bit more complex but at a basic level this is correct. If you want more information on how they function I encourage you to read the following articles

The primary advantage of closures is essentially what you demonstrated above. It allows you to write the code in a more natural, straight forward fashion without having to worry about the implementation details of how the lambda expression is generated (generally)

Consider for example how much code you would have to write in the abscence of closures

class Helper {
  private int _id;
  public Helper(int id) { 
    _id = id;
  }
  public bool Filter(Person p) {
    return p.id == _id;
  }
}

void FindPersonsByID(int id) {
  Helper helper = new Helper(id);
  gurus.FindAll(helper.Filter);
}

All of this just to express the concept of using a parameter inside of a delegate.

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