“Everything in Ruby is an object” is a statement that almost every Rubiers has heard. But Einstein’s theory of relativity says: Nothing is absolute!
Hmmm, so let’s see, is there anything in Ruby that isn’t an object?
1. Block
Block is a block of sequentially executed statements enclosed in {} or do end . Block is not an object, and therefore, it has no name. It also cannot be assigned to any variables. Blocks cannot be reused and cannot be stored. Block is passed to a method and is executed at the keyword yeild
1 2 3 4 5 6 | def say_something_to_xuantai yield "Xuan Tai" end say_something_to_xuantai { |welcome| "Welcome to Ruby, #{welcome}" } |
2. Conditional
Conditional makes it possible to execute statements according to the desired condition. In Ruby, there are two commonly used conditionals: If - else and case - when . So what’s the difference between these 2 items? When to use if - else , when to use case - when ?
a. if – else
If – else is a conditional type that is evaluated sequentially from top to bottom, and it only executes statements in the conditional branch that is satisfied. With if - else , we can consider many different conditions or combinations of conditions, and the preceding conditions will be evaluated first.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | def say_the_number(a) if a > 2 puts "greater than 2" elsif a < 5 puts "less than 5" elsif a == 4 puts "4" else puts "It's a number" end end say_the_number(1) # less than 5 say_the_number(3) # greater than 2 say_the_number(4) # greater than 2 |
According to the above example, it is clear that when passing 3 and 4 in, it satisfies the condition < 5 . However, it has satisfied the condition > 2 before, so it will not consider the conditions below.
b. case – when
case - when is also a conditional statement. However, this statement can only compare with 1 variable and each expression is a unique value. The values to be compared in the expression can be a number, a string, a symbol or even an array
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | ex1: case a when 0 puts "It's a number" when "x" puts "It's a string" else puts "It's nothing" end ex2: case a when *(1..10) puts "Less than 11" when *(11..20) puts "Less than 21" else puts "It's nothing" end |
c. When to use If - else , when to use when - case ?
if - else can be used for all cases. However, when the conditional expressions are single expressions and have independent, non-overlapping values, we should use when - case to make the code more neat and easy to understand.
3. Methods
Methods can simply be understood as the actions of an object, and therefore it is not an object.
4. Operators
Operators is a set of operators used to perform operations with objects. In fact, these operators are methods. And when performing the math a + b , in fact + is the method of a , and b is the argument. And because it is a method, we can completely override these operators.
1 2 3 4 5 6 7 8 | a = "Xin chao" class << a def +(string) return "#{self} Xuan Tai #{string}" end end => a + "dep trai" # Xin chao Xuan Tai dep trai |
Like the example above, I have overridden the + operator on my own object a(class String). And now the result of a + ... will always include the string Xuan Tai
Summary:
Through this, we can already know that, in Ruby not all are objects. Which is more precise: In Ruby, almost everything is an object.
Thank you readers, if there is something wrong with my article, please feel free to scold me. I will always humble myself to listen to have the opportunity to gain more knowledge. Thank you.