Method of Ruby Meta programming

This article mainly introduces the method_missing of Ruby Meta programming, this article introduces a phenomenon that causes death cycle when using method_missing, the friend who need can refer to the following

We know the top-level domain, what is the self of the domain defined?

The code is as follows:

Puts self #main

Puts Self.class #Object

We know that when a method is invoked, if there is no object to accept, the default is self, such as:

The code is as follows:

def tell_me_who

Puts self

End

Tell_me_who #main

A method call is a step to find out whether an instance method of the current object's class exists or not, and if so, call the method, and if it does not exist, view superclass until Basicobject finds the method, and the kernel method_ is invoked. Missing () method, and an error, such as

The code is as follows:

Error:test.rb:8: undefine:undefined local variable or method "Ask" for Main:object (Nameerror)

Pay attention to the error information, we can find that when we call a nonexistent variable, it will be traced back to the kernel method_missing method, here to note slightly.

Verify:

The code is as follows:

Puts self #main

Puts Self.class #Object

def self.method_missing (Name,*arg)

Puts "#{name} is not exist!"

End

Puts ask #ask isn't exist!

One case causes a bug:

The code is as follows:

def self.method_missing (Name,*arg)

1.times do

Puts Method_name=name

End

Puts "#{method_name} is not exist!"

End

Ask #变量或者方法

Intent: Make any undefined variable or method print once

But is this a dead loop? See the problem?

Ask is executed, but without the definition ask, it will go to method_missing,

Method_name in the block of times, out of scope, so will execute the method_missing, into a dead loop.