Ruby Predicate Methods

What is a predicate method?

A method that returns true or false is called a “predicate method”.
In Ruby, the naming convention for predicate methods ends with a question mark.
This improves readability by making Ruby code read more like English.
In this article, we are going to list the handiest predicate methods in ruby with examples.

.odd?

3.odd?
true

.even?

5.even?
false

.between?

7.between?(1, 9)
true

11.between?(1, 9)
false

.zero?

2.zero?
false

0.zero?
true

.include?

[1, 2, 3].include?(3)
true

[1, 2, 3].include?(4)
false

"Hello Ruby".include?("by")
true

"Hello Ruby".include?("m")
false

.key? & .value?

{ num: 9 }.key?(:wrong)
false

{ str: "Hello" }.value?("Hello")
true

.has_key? & .has_value?

{ num1: 9, num2: 7 }.has_key?(:num2)
true

{ lang1: "Ruby", lang2: "JavaScript" }.has_value?("Python")
false

.start_with? & it's opposite .end_with?

"Hello Ruby".start_with?("by")
false

"Hello Ruby".end_with?("by")
true

.is_a?

4.is_a? String
false

"Hello".is_a? String
true

.empty?

[].empty?
true

[1, 2].empty?
false

These ones are the handiest ruby predicate methods and still, there are more please visit Ruby-Docs to see the whole list.