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  • Implicit and Explicit Blocks in Ruby

    @shweta.singh
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    Blocks are basically a group of code that can be stored in a parameter and can be executed. There are majorly two ways of doing this:

     

    1) Implicit:

    In implicit, it is a nameless block and it is not passed as a parameter, it is executed using yield.

    Lets see an example suppose we want to execute some code by adding begin..rescue, so every time in every function we need to write the begin rescue like this:

    1. def get_country_date(id)
    2.    begin
    3.        ## The real code
    4.        @country = Country.find(id)
    5.     rescue StandardError => e
    6.        Rails.logger.error e.message
    7.     end
    8. end


    So excepting the line that finds country using id, we need to rewrite the code everyplace wherever we want to use begin..rescue. But if we use implicit version of blocking we can write the code like this:

    1. def get_country_data(id)
    2.   with_rescuing { @country = Country.find(id) }
    3. end
    4.  
    5. def with_rescuing
    6.     begin
    7.         ## The real code
    8.         ## Here the calling function gets called and executed
    9.         yield
    10.      rescue StandardError => e
    11.           Rails.logger.error e.message
    12.       end
    13. end

     

    2) Explicit:

    In case of explicit blocking we can create a block and can give a name to it explicitly, so that whenever it is needed we can pass it as a parameter and then we can call it using that parameter

    2. def get_country_data(id)
    3.    with_rescuing { @country = Country.find(id) }
    4. end
    5.  
    6. def with_rescuing(&get_country_block)
    7.     begin
    8.         ## The real code
    9.         ## here we can call the calling function
    10.         get_country_block.call
    11.      rescue StandardError => e
    12.         Rails.logger.error e.message
    13.      end
    14. end

    Thus we can see the blocks are one of the best thing in rails to remove the boilerplate code and also they solve the callback problems.

    Ruby on Rails Ruby blocks
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