这总是很危险的，特别是当你在构造函数中分配资源时;根据你的语言，析构函数不会被调用，所以你需要手动清理。这取决于在您的语言中对象的生命周期何时开始。

我真正这么做的唯一一次是在某个地方出现了安全问题，这意味着对象不应该，而不是不能，被创建。

是的，如果构造函数未能构建其内部部分之一，则它可以(通过选择)有责任抛出(并以某种语言声明)一个显式异常，这在构造函数文档中有适当的说明。

This is not the only option: It could finish the constructor and build an object, but with a method 'isCoherent()' returning false, in order to be able to signal an incoherent state (that may be preferable in certain case, in order to avoid a brutal interruption of the execution workflow due to an exception) Warning: as said by EricSchaefer in his comment, that can bring some complexity to the unit testing (a throw can increase the cyclomatic complexity of the function due to the condition that triggers it)

如果它因为调用者而失败(比如调用者提供了一个空参数，而被调用的构造函数需要一个非空参数)，构造函数无论如何都会抛出一个未检查的运行时异常。

构造函数的任务是使对象进入可用状态。关于这个问题，基本上有两种观点。

一组人赞成两阶段建设。构造函数只是将对象带入一个休眠状态，在这种状态下它拒绝做任何工作。还有一个额外的函数来进行实际的初始化。

我一直不明白这种方法背后的原因。我坚决支持单阶段构造，即对象在构造后完全初始化并可用。

如果单阶段构造函数未能完全初始化对象，则应该抛出。如果对象不能初始化，则必须不允许它存在，因此构造函数必须抛出。

我所见过的关于异常的最好建议是，当且仅当替代方案是未能满足post条件或保持不变时，抛出异常。

该建议将不明确的主观决策(这是个好主意吗)替换为基于设计决策(不变条件和后置条件)的技术精确问题。

Constructors are just a particular, but not special, case for that advice. So the question becomes, what invariants should a class have? Advocates of a separate initialization method, to be called after construction, are suggesting that the class has two or more operating mode, with an unready mode after construction and at least one ready mode, entered after initialization. That is an additional complication, but acceptable if the class has multiple operating modes anyway. It is hard to see how that complication is worthwhile if the class would otherwise not have operating modes.

请注意，将setup推入单独的初始化方法中并不能避免抛出异常。构造函数可能抛出的异常现在将由初始化方法抛出。如果为未初始化的对象调用类中所有有用的方法，都必须抛出异常。

还要注意，避免构造函数抛出异常的可能性是很麻烦的，在许多标准库中在许多情况下是不可能的。这是因为这些库的设计者认为从构造函数抛出异常是个好主意。特别是，任何试图获取不可共享或有限资源(例如分配内存)的操作都可能失败，而这种失败通常在OO语言和库中通过抛出异常来表示。

There is generally nothing to be gained by divorcing object initialization from construction. RAII is correct, a successful call to the constructor should either result in a fully initialized live object or it should fail, and ALL failures at any point in any code path should always throw an exception. You gain nothing by use of a separate init() method except additional complexity at some level. The ctor contract should be either it returns a functional valid object or it cleans up after itself and throws.

考虑一下，如果实现了单独的init方法，仍然必须调用它。它仍然有可能抛出异常，它们仍然必须被处理，而且它们实际上总是必须在构造函数之后立即被调用，除了现在你有4种可能的对象状态而不是2种(IE，已构造，初始化，未初始化，失败vs只是有效和不存在)。

In any case I've run across in 25 years of OO development cases where it seems like a separate init method would 'solve some problem' are design flaws. If you don't need an object NOW then you shouldn't be constructing it now, and if you do need it now then you need it initialized. KISS should always be the principle followed, along with the simple concept that the behavior, state, and API of any interface should reflect WHAT the object does, not HOW it does it, client code should not even be aware that the object has any kind of internal state that requires initialization, thus the init after pattern violates this principle.

如果无法在构造函数中初始化对象，则抛出异常，一个例子是非法参数。

根据一般经验，应该尽可能快地抛出异常，因为当问题的根源接近发出错误信号的方法时，这会使调试变得更容易。