访问器的目的是什么？ [英] What is the purpose of accessors?
问题描述
有人可以帮助我理解获取& set ？
为什么需要它们？我可以只设置一个公共变量。
Can somebody help me understand the get & set?
Why are they needed? I can just make a public variable.
推荐答案
警告：我假设您已经
什么是属性？
属性是语言元素，可让您避免使用重复的 getXYZ（）访问器和 setXYZ（）变异器技术
Warning: I am assuming you already know about object-oriented programming.
What are properties?
Properties are language elements that allow you to avoid the repetitive getXYZ() accessors and setXYZ() mutators techniques found in other languages, like Java.
它们旨在解决以下问题：
They aim to solve the following problems:
-
说
get和set在每次访问或值突变的开始都是令人讨厌和分散注意力的。
Saying
getandsetin the beginning of every access or mutation of a value is annoying and distracting.
在Java中，您通常会说：
In Java, you often say:
class person
{
private int _age;
public void setAge(int value) { /*check value first, then set _age*/ }
public int getAge() { return this._age; }
}
然后不断说：
if (person.getAge() > blah || person.getAge() < 10)
{
person.setAge(5);
}
过一会儿，得到和 set 变得很烦人。
After a while, the get and set become rather annoying.
提供对实际变量的直接访问会破坏封装，所以这不是一个选择。
Providing direct access to the actual variable breaks encapsulation, so that's not an option.
如何使用？
使用 就像变量一样。您像对变量一样对它们进行读/写。
How are they used?
They are used just like variables. You read/write to them just like variables.
它们是 创建的方法。您定义了一对方法：
They are created as methods. You define a pair of methods that:
-
返回属性的当前值。通常，它只不过是以下内容：
Return the current value of the property. Oftentimes, this is nothing more than something like the following:
class Person
{
private int _age; //Declare the backing field
public int Age
{
get { return this._age; }
set { ... }
}
}
设置属性的值：
Set the value of the property:
class Person
{
public int Age
{
get { ... }
set
{
if (value < 0) //'value' is what the user provided
{ throw new ArgumentOutOfRangeException(); } //Check validity
this._age = value;
}
}
}
其他说明：
自动实现的属性
C＃3.0引入了自动实现的属性：
Other notes:
Auto-implemented Properties
C# 3.0 introduced auto-implemented properties:
public int Age { get; set; }
这等效于：
private int _age; //The name is auto-generated
public int Age { get { return this._age; } set { this._age = value; } }
为什么存在？
它可以帮助您避免破坏客户端可执行文件中的更改。
假设您很懒，不想键入整个内容，并决定公开展示变量。然后，您创建一个可读取或写入该字段的可执行文件。然后，您改变主意，并决定实际上需要某个属性，因此将其更改为一个。
Let's say you're lazy and don't want to type the whole thing, and decide to expose a variable publicly. You then create an executable that reads from or writes to that field. Then you change your mind and decide that you in fact needed a property, so you change it to one.
会发生什么？
依赖的可执行文件会中断，因为代码不再有效。
The depending executable breaks, because the code is no longer valid.
自动实现的属性可以帮助您避免这种情况，而无需
Auto-implemented properties help you avoid that, without extra redundancy in your initial code.
Indexers扩展了属性语法，使您可以 index 对象（惊奇！），就像数组一样。
对于C ++用户：这类似于重载 operator [] 。
Indexers extend the property syntax to let you index objects (surprise!), just like arrays.
For C++ users: This is similar to overloading operator [].
例如：
private int[] _elements;
public int this[int index] //Indexed property
{
get { return this._elements[index]; }
set
{
//Do any checks on the index and value
this._elements[index] = value;
}
}
然后像一样使用它们obj [5] = 10; ，等效于调用 obj set 方法>的索引器。
实际上， System.Collections.Generic.List< T> 被索引：
You then use them like obj[5] = 10;, which is equivalent to calling the set method of obj's indexer.
In fact, System.Collections.Generic.List<T> is indexed:
var list = new List<int>();
list.Add(10);
list[0] = 5; //You're indexing list, as though it were an array!
不是很整洁吗？ ：）
属性还有很多其他功能，但并非所有功能都可以在C＃：
There are many more features to properties, not all of which are available in C#:
- 参数化的属性，其中索引器是一种特殊的属性
- 字母/字母访问修饰符（在C＃中）
- 多个getter或setter（不在C＃中）
- Et cetera
- Parametrized properties, of which indexers are a special kind
- Getter/setter access modifiers (in C#)
- Multiple getters or setters (not in C#)
- Et cetera
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