base() 和 this() 构造函数最佳实践 [英] base() and this() constructors best practices

问题描述

在什么条件下我应该在我的构造函数的括号之后(或者甚至在代码的其他地方)调用 :base() 和 :this() 构造函数调用).这些电话什么时候是好的做法，什么时候是强制性的?

Under what conditions am I supposed to make the :base() and :this() constructor calls following my constructor's parentheses (or even in other places in the code). When are these calls good practices and when are they mandatory?

推荐答案

: base(...)

如果省略对基构造函数的调用，它将自动调用默认的基构造函数.

If you omit the call to a base constructor it will call the default base constructor automatically.

如果没有默认构造函数，则必须显式调用基构造函数.

It is mandatory to call a base constructor explicitly if there is no default constructor.

即使有默认构造函数，您可能仍然希望调用与默认构造函数不同的构造函数.在这种情况下，您可能仍然希望使用 base(foo, bar) 来调用与基本构造函数不同的构造函数.

Even if there is a default constructor you may still wish to call a different constructor than the default constructor. In this case you may still wish to use base(foo, bar) to call a different constructor than the base constructor.

我不认为在您想调用基类默认构造函数时省略 base() 是一种不好的做法，尽管如果您喜欢明确我认为包括它.这是一个品味问题.

I do not consider it to be a bad practice to omit base() when you want to call to the base class default constructor, although if you like to be explicit I see no harm in including it. It is a matter of taste.

: this(...)

此语法允许您在同一类中调用具有不同签名的构造函数.这样做从来不是强制性的，但有时会很有用.

This syntax allows you to call one constructor with a different signature from another within the same class. It is never mandatory to do this, but can sometimes be useful.

一个有用的例子是在构造函数中重用公共代码.例如，在 C# 3.5 或更早版本中，您可能希望在构造函数上模拟可选参数:

An example of when it can be useful is for reusing common code in the constructors. For example in C# 3.5 or before you may want to simulate optional parameters on a constructor:

Foo(int x, int y)
{
     this.x = x;
     this.y = y;
}

Foo(int x) : this(x, 10) {}  // y defaults to 10

现在可以使用 C# 4.0 可选参数，这减少了对这种方法的需求.

With C# 4.0 optional parameters are now available which reduces the need for this approach.

在构造函数中重用代码的另一种方法是将其分解为一个静态函数，该函数由每个希望使用它的构造函数调用.

An alternative way to reuse code in constructors is to factor it out into a static function which is called from each constructor that wishes to use it.

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