Feature #12608
Updated by LucianCancescu (Lucian Cancescu) almost 8 years ago
Hi, I would like to propose the replacement of the `unless` statement in Ruby. # Problem description: Unless is complex and my arguments are: * I often see in projects `unless ... else`: ~~~ ruby unless user redirect_to_login else render_profile end ~~~ * Using `unless` with conditionals makes it very hard to understand: ~~~ ruby unless user || tenant do user_and_tenant_are_present end ~~~ Put an else to the conditional above and you can easily spend a few minutes to correctly understand what the code does. Ruby is focuses on simplicity. I find both the examples above speaking against it. I have seen many Ruby projects, written by different people, and in most of them you see `unless` being abused in some way. There is another aspect, when you see unless you have to keep a `not` in mind. The problem with that is that you have to negate all you read afterwards. You have to remove the negation when an else appears and you have to carefully read the negation with parenthesis in mind when `unless` contains boolean conditions. It's a huge complexity which can be avoided by simply using something else. # Proposed solution: How can we reduce the complexity? Other languages, for instance Swift, have introduced the `guard` [1] statement. `guard` can replace `unless` in Ruby and the complex scenarios from above would become impossible: Example 1 from above translates to: ~~~ ruby guard user else return user_is_missing end # do something with the user render_profile ~~~ Example 2 from above translates to: ~~~ ruby guard user && and tenant else return user_or_tenant_missing end # do something with the user and the tenant ~~~ Not only the conditions become easier to read, but it reduces a lot the complexity of the code. My suggestion is to add `guard` to the language and make it replace `unless`. What do you think? Thanks, Lucian [1] Guard in Swift: https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Statements.html#//apple_ref/swift/grammar/guard-statement