Ruby methods without parameters

In this article, we will take a look at methods that don’t have any parameters.

This article is divided into the following sections:

• Syntax
• If you pass some arguments, then ruby will display an error
• Even if a method doesn’t have defined parameters, the method still takes a block
• Conclusions

Syntax

Let’s begin the classification of methods by parameters from the simplest case — when a method has no parameters at all. You already could saw similar methods before, let’s look at them again:

def cat 
  puts "Meow! Meow!"
end 
def dog 
  puts "Raf! Raf!"
end 
def cow 
  puts "Moooooo!"
end 
cat
dog
cow

produces:

Meow! Meow!
Raf! Raf!
Moooooo!
=> nil

If you pass some arguments, then ruby will display an error

In some programming languages, if we pass arguments, and they are not defined in the list of parameters, then this is not considered as an error — the code will still be executed. In ruby we have the different situation, if you want to pass arguments to a method for which there are no parameters, then the program will terminate its execution.

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Example:

def cat 
  puts "Meow! Meow!"
end 
cat("argument")

produces:

wrong number of arguments (given 1, expected 0)
(repl):1:in `cat'
(repl):5:in `<main>'

Even if a method doesn’t have defined parameters, the method still takes a block

Let’s see how it looks like:

def cat 
  puts "Meow! Meow!"
  yield 
end 
cat { puts "Hello from block!" }

produces:

Meow! Meow!
Hello from block!
=> nil

Conclusions

- in ruby, as in other programming languages, there are methods that haven’t parameters;
- a method without parameters can receive a block;
- if we pass arguments to a method which haven’t parameters, then ruby will stop the code execution and show us an error.

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