如何在所有带有参数传递的类函数调用之前/之后运行方法? [英] How to run a method before/after all class function calls with arguments passed?

问题描述

有一些有趣的方法可以在类中的每个方法之前运行一个方法，例如

There are some interesting ways to run a method before every method in a class in questions such as Python: Do something for any method of a class?

但是，该解决方案不允许我们传递参数.

However that solution doesn't let us pass arguments.

在>捕获" ;函数调用之前/之后类中所有函数的事件，但我不想回过头来装饰我所有的类.

There's a decorator solution on Catch "before/after function call" events for all functions in class but I don't want to have to go back and decorate all my classes.

是否有一种方法来运行前/后操作，该操作取决于为对象方法的每次调用传递的参数?

Is there a way to run a pre/post operation that's dependent on the arguments passed for every invocation of an object's method?

示例:

class Stuff(object):
    def do_stuff(self, stuff):
        print(stuff)

a = Stuff()
a.do_stuff('foobar')
"Pre operation for foobar"
"foobar"
"Post operation for foobar"

推荐答案

因此，经过大量实验，我发现了这一点.

So I figured it out after a lot of experimentation.

基本上，在元类的__new__中，您可以遍历类的名称空间中的每个方法，并用运行前逻辑，函数本身和后逻辑的新版本替换正在创建的类中的每个方法. .这是一个示例:

Basically in the metaclass' __new__ you can iterate through every method in the class' namespace and swap out every method in the class being created with a new version that runs the before logic, the function itself, and the after logic. Here's a sample:

class TestMeta(type):
    def __new__(mcl, name, bases, nmspc):
        def replaced_fnc(fn):
            def new_test(*args, **kwargs):
                # do whatever for before function run
                result = fn(*args, **kwargs)
                # do whatever for after function run
                return result
            return new_test
        for i in nmspc:
            if callable(nmspc[i]):
                nmspc[i] = replaced_fnc(nmspc[i])
        return (super(TestMeta, mcl).__new__(mcl, name, bases, nmspc))

请注意，如果按原样使用此代码，它将为 init 和其他内置函数运行pre/post操作.

Note that if you use this code as is it will run the pre/post operation for init and other builtin functions as well.

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