Differences between Ruby's methods, instance_methods, and Method

Class A def self. ask1 puts "the method of Class" End def ask2 puts "the method of instance" endend
 

# Method of the Instance Object of the class. The method belongs to the new instance object generated by the class.
P a. Methods. Length
P a. Class. instance_methods.length
P a. instance_methods.length
P a. public_methods.length
P a. Class. public_instance_methods.length
Output: 50

The preceding five methods are used to output instance objects.

# Add a single-piece Method for instance

 
Def A. tellendp A. Methods. lengthp A. Class. instance_methods.lengthp A. Category A. public_methods.lengthp A. Class. public_instance_methods.length
 

Output: 51 50 51 50
Note: The instance_methods of a class includes only the instance methods it owns, and does not include the methods of a single class. In addition, the methods method is actually the same as public_methods, which is different from private_methods.

# Class method, which belongs to the class itself
P a. Methods. Length
P a. Class. instance_methods.length
P a. public_methods.length
P a. Class. public_instance_methods.length

Output: 87 86 87 86

Note: 1.8.6 and 1.9.2 are different based on different versions.

Now let's talk about the method.

This method belongs to the method class. The most common method is to check the number of parameters of the method, as shown below:

 
Class A def self. ask1 (N1, N2) puts "the method of Class" End def ask2 (N1) puts "the method of instance" endenda =. newp. method (: ask2 ). arityp. method (: ask1 ). arity
 

Output: 1 2

Here we will not stick to the introduction of all the methods, but will introduce the more common methods.