python super函数在django模型中的使用 [英] use of python super function in django model

问题描述

这是我正在阅读的 django 教程中的一些代码.我以前从未在 python 中遇到过 super 函数，这里使用的方式与我在网上看到的示例不同.即，通常当您使用 super 时，您不是有多个类吗?它在最后一行:super(Snippet, self).save(force_insert, force_update)您能否准确解释一下那里发生了什么以及编写它的另一种方法是什么.好像 save 方法在这里调用了自己?

Here's some code in a django tutorial that I'm going through. I've never come across the super function in python before and the way it's used here is different from the examples I've seen online. I.e., usually when you use super, don't you have multiple classes? It's in the last line: super(Snippet, self).save(force_insert, force_update) Could you explain exactly what's going on there and what would be an alternative way to write that. It just seems like the save method is calling itself here?

class Snippet(models.Model):
    title = models.CharField(max_length=255)
    language = models.ForeignKey(Language)
    author = models.ForeignKey(User)
    description = models.TextField()
    description_html = models.TextField(editable=False)
    code = models.TextField()
    highlighted_code = models.TextField(editable=False)
    tags = TagField()
    pub_date = models.DateTimeField(editable=False)
    updated_date = models.DateTimeField(editable=False)

    class Meta:
        ordering = ['-pub_date']

    def __unicode__(self):
        return self.title

    def save(self, force_insert=False, force_update=False):
        if not self.id:
            self.pub_date = datetime.datetime.now()
        self.updated_date = datetime.datetime.now()
        self.description_html = markdown(self.description)
        self.highlighted_code = self.highlight()
        super(Snippet, self).save(force_insert, force_update)

推荐答案

super(Snippet, self) 使 Python 在 MRO 类的 self(即 self.__class__.mro() 用于 next 列在 Snippet 之后的类.它返回一个 super 对象，该对象充当该类的代理.也就是说，调用 super 上的方法> 对象就像在类上调用该方法一样.

super(Snippet, self) causes Python to look in the MRO of the class of self (i.e. self.__class__.mro() for the next class listed after Snippet. It returns a super object which acts as a proxy for that class. That is, calling a method on the super object acts like calling that method on the class.

super(Snippet, self).save(...) 调用该类的 save 方法，将 self 绑定到第一个参数.

super(Snippet, self).save(...) calls that class's save method, with self bound to the first argument.

所以super(Snippet, self).save(...) 不会调用Snippet 的save 方法；它将调用其他类的 save 方法.人们很容易认为这个其他类"是 Snippet 的父类"或超类"，也就是说，models.Model，但这可能不是真的，这样理解 super 是绝对错误的.super(Snippet, self) 最终代表哪个类取决于 self ，特别是它的类的 MRO.

So super(Snippet, self).save(...) will not call Snippet's save method; it will call some other class's save method. It is tempting to think this "other class" is the "parent class" or "superclass" of Snippet, that is, models.Model, but that may not be true and it is absolutely wrong to apprehend super this way. Which class super(Snippet, self) ultimately represents depends on self and in particular its class's MRO.

可以在 这里.

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