[Ruby] Exception handling in functions

Introduction

This article is a supplement to a number of exception handling. Specifically, I will leave the result of verifying the pattern not introduced in the article.

environment

Use in functions

In the function, you can write as follows.

def method
  puts "hoge"
  a = 1 / 0
rescue ZeroDivisionError
  puts $!
end

It is a form that omits begin and end. In the case of such a shape

a = 1 / 0

Is obvious that will cause an error. But what if:

def method
  #Huge processing 1
  #Processing that is likely to cause an error
  #Huge processing 2
rescue StandardError
  puts $!
end

By the way, it is doubtful that the person who sees this code can immediately see the processing that is likely to cause an error. In that case, I think you should dare to write begin and end.

def method
  #Huge processing 1
  begin
    #Processing that is likely to cause an error
  rescue StandardError
    puts $!
  end
  #Huge processing 2
end

This way you can see where the error is likely to occur and you don't have to scroll a lot to see the rescue. By the way, if you return with rescue, the huge amount of process 2 will not be processed, so if you definitely want it to be processed, put it in ensure.

def method
  #Huge processing 1
  begin
    #Processing that is likely to cause an error
  rescue StandardError
    puts $!
    return
  ensure
    #Huge processing 2(Even if there is a return in rescue, it will be processed)
  end
end

If there are multiple processes that are likely to cause an error, I think it is simple to write them together at the end of the function. Writing begin, rescue, end every time will make it less readable. Everything is right.

def method
  #Processing that is likely to cause various errors

  #Other processing

rescue ZeroDivisionError, ArgumentError
  puts $!
rescue StandardError
  puts $!
  puts $@
end

By the way, if you write StandardError first, this guy will do most of the error handling. So let's start with the child class.

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