The best way I can describe what I'm looking for is to show you the failed code I've tried thus far:
case car
when ['honda', 'acura'].include?(car)
# code
when 'toyota' || 'lexus'
# code
end
I've got about 4 or 5 different when situations that should be triggered by approximately 50 different possible values of car. Is there a way to do this with case blocks or should I try a massive if block?
In a case statement, a , is the equivalent of || in an if statement.
case car
when 'toyota', 'lexus'
puts 'brand is part of the Toyota Motor Corporation'
else
puts 'some other brand'
end
# NOTE: You may use `then` after the when condition.
# It is frequently used to place the body of the `when` on a single line.
case car
when 'toyota', 'lexus' then puts 'brand is part of the Toyota Motor Corporation'
else puts 'some other brand'
end
when "toyota", "lexus", I get: unexpected tSTRING_BEG, expecting keyword_do or '{' or '(' (SyntaxError). However, when I write this: when "toyota","lexus", it works. The only difference is a space after comma.
or or || here because the when takes a series of comma-separated expressions to the right of it, not a single identifier. Because of this, if you had when a or b, it's not clear whether this is to be taken as the equivalent of when a, b or when (a or b), the latter of which evaluates the expression a or b first before throwing it into the when. It's more surprising and less easy to handle for the language to have tokens that change behavior based on context, and then you wouldn't be able to use a real or expression on the right side of a when.You might take advantage of ruby's "splat" or flattening syntax.
This makes overgrown when clauses — you have about 10 values to test per branch if I understand correctly — a little more readable in my opinion. Additionally, you can modify the values to test at runtime. For example:
honda = ['honda', 'acura', 'civic', 'element', 'fit', ...]
toyota = ['toyota', 'lexus', 'tercel', 'rx', 'yaris', ...]
...
if include_concept_cars
honda += ['ev-ster', 'concept c', 'concept s', ...]
...
end
case car
when *toyota
# Do something for Toyota cars
when *honda
# Do something for Honda cars
...
end
Another common approach would be to use a hash as a dispatch table, with keys for each value of car and values that are some callable object encapsulating the code you wish to execute.
Remember switch/case (case/when, etc.) is just comparing values. I like the official answer in this instance for a simple or'd string list comparison, but for more exotic conditional / matching logic,
case true
when ['honda', 'acura'].include?(car)
# do something
when (condition1 && (condition2 || condition3))
# do something different
else
# do something else
end
Another nice way to put your logic in data is something like this:
# Initialization.
CAR_TYPES = {
foo_type: ['honda', 'acura', 'mercedes'],
bar_type: ['toyota', 'lexus']
# More...
}
@type_for_name = {}
CAR_TYPES.each { |type, names| names.each { |name| @type_for_name[type] = name } }
case @type_for_name[car]
when :foo_type
# do foo things
when :bar_type
# do bar things
end
you could do something like this (inspired by @pilcrow's answer):
honda = %w[honda acura civic element fit ...]
toyota = %w[toyota lexus tercel rx yaris ...]
honda += %w[ev_ster concept_c concept_s ...] if include_concept_cars
case car
when *toyota
# Do something for Toyota cars
when *honda
# Do something for Honda cars
...
end
In a case statement, equivalent of && in an if statement.
case coding_language when 'ror' && 'javascript' # code end
