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ricardo leiva sikic
Asked: 2020-11-12 10:06:40 +0800 CST 2020-11-12 10:06:40 +0800 CST

Formulation consultation

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Hello, I have a small query, in a rails application, I have seen this a lot:

args[:where] && args[:where][:establishment_id]

The query is that both mean, are they argument hash of ruby? the second looks for "where the key is establishment_id?

ruby-on-rails

1 Answers

  1. Best Answer

    I'm assuming they should use it so the code doesn't crash if it's args[:where]not present.
    For example:

    [1] pry(main)> args = { where: { establishment_id: 1 } }
=> {:where=>{:establishment_id=>1}}
[2] pry(main)> args[:where] && args[:where][:establishment_id]
=> 1

    then in case en argswas not defined :where, the code would not crash.

    [3] pry(main)> args = {}
=> {}
[4] pry(main)> args[:where] && args[:where][:establishment_id]
=> nil

    Given the last definition of args, if you access directly :establishment_idwithout checking that :where, your code will fail:

    [5] pry(main)> args = {}
=> {}
[6] pry(main)> args[:where][:establishment_id]
NoMethodError: undefined method `[]' for nil:NilClass
from (pry):5:in `<main>'

    if what bothers you is seeing so much args[:where] &&, another way to achieve the same thing is with .try:

    [7] pry(main)> args = {}
=> {}
[8] pry(main)> args[:where].try(:[], :establishment_id)
=> nil

    And if you're using ruby ​​2.3 or higher, you can use .digand make your code even simpler:

    [9] pry(main)> args = {}
=> {}
[10] pry(main)> args.dig(:where, :establishment_id)
=> nil
[11] pry(main)> args = { where: { establishment_id: 1 } }
=> {:where=>{:establishment_id=>1}}
[12] pry(main)> args.dig(:where, :establishment_id)
=> 1
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