Smalltalk中的自我和自己之间有什么区别? [英] What is the difference between self and yourself in Smalltalk?

问题描述

在Smalltalk中，方法主体中经常有两个术语:self和yourself.

In Smalltalk, there are two terms often found within a method body: self and yourself.

它们之间有什么区别?

推荐答案

保留字self是一个伪变量(您不能分配给它)，它引用使用该方法的当前接收者.另一方面，yourself是一条消息，您可以将其发送到任何对象以获得该对象.

The reserved word self is a pseudo variable (you cannot assign to it) that refers to the current receiver of the method where it is used. On the other side yourself is a message you can send to any object to get that very same object.

yourself的实现是

yourself
    ^self

表示消息yourself将按照我刚才的解释行事.

meaning that the message yourself will behave as I just explained.

yourself存在的原因是为了支持消息级联，您将其作为最后一条消息放置在该消息中，以确保结果表达式将与接收方一起回答:

The reason why yourself exists is to support message cascading, where you put it as the last message to make sure the resulting expression will answer with the receiver:

^receiver
   msg1;
   msg2;
   yourself

如果msg2可能回答的内容与receiver不同，则可以附加yourself消息以忽略该答案，而返回receiver.当然，您可以通过编写以下内容来达到相同的结果:

If msg2 might answer with something different from the receiver you can append the yourself message to ignore that answer and return receiver instead. Of course you could have achieved the same result by writing:

receiver
   msg1;
   msg2.
^receiver

由于这两个示例都很简单，因此可能很难理解其优势.但是，请考虑receiver不是变量，而是复杂的表达式，例如.

Because of the simplicity of these two examples, it might be hard to understand what the advantage would be. However, consider that receiver is not a variable but a complex expression, something like.

^(self msg: arg1 arg: arg2)
   msg1;
   msg2;
   yourself.

在不使用yourself的情况下，您必须添加一个临时文件来保存接收器的值以实现相同的目的:

Without using yourself you would have to add a temporary to save the value of the receiver to achieve the same:

| answer |
answer := self msg: arg1 arg: arg2.
answer
   msg1;
   msg2.
^answer

有点冗长.

总而言之，self是一个保留字，它指向当前的接收者，而yourself只是为了方便起见而使用的常规方法.

To summarize, self is a reserved word that refers to the current receiver and yourself is just a regular method that is there just for convenience.

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