Case with strings

ruby-talk
1

A similar problem:
case key.strip
                when "c" "Synopsis"
                when "s" "Category"
                when "io" "Inputs and outputs"
                when "processing" "Processing type"
                when "d" "Description"
                when "n" "Notes"
                when "e" "Examples"
                when "h" "Element handlers"
                when "a" "See also"
                else puts "Unknown key"
        end
        if key.strip == "a"
                puts "This gives output"
        end
unknown key
This gives output

What am I doing wrong? I'm a really Ruby newbie so probably I'm looking at
it the wrong way...

···

--
"May the source be with you"

2

Aquila wrote:

case key.strip
                when "c" "Synopsis"
                when "s" "Category"
                when "io" "Inputs and outputs"
                when "processing" "Processing type"
                when "d" "Description"
                when "n" "Notes"
                when "e" "Examples"
                when "h" "Element handlers"
                when "a" "See also"
                else puts "Unknown key"
        end
        if key.strip == "a"
                puts "This gives output"
        end
unknown key
This gives output

What am I doing wrong? I'm a really Ruby newbie so probably I'm looking at
it the wrong way...

You forget to put "puts" before you're Strings. This will work:

case key.strip
   when "c" puts "Synopsis"
   when "s" puts "Category"
   ...
end

And this will also work and require less repetition:

puts case key.strip
   when "c": "Synopsis"
   when "s": "Category"
   ...
end

Though I wonder if you're not better of with a Hash:

puts({
   "c" => "Synopsis",
   "s" => "Category",
   ...
}[key.strip])

3

Aquila:

case key.strip
                when "c" "Synopsis"

# You need the keyword 'then' here.

when 'c' then 'Synopsis'
# or alternatively:
when 'c'; 'Synopsis'

# And you're likely to write something like this:

answer = case key.strip
  when 'c' then 'Synopsis'
  # etc.
end
# now work with answer

# Consider, too, using a hash. It does what you want in a very direct and
# clean way.

# Malte

4

Florian Gross wrote:

<snip>

And this will also work and require less repetition:

puts case key.strip
   when "c": "Synopsis"
   when "s": "Category"
   ...
end

Actually the code has less duplication, this was just an example. But why
doesn't this work:
def keyToName(key)
        case key.strip
....
                when "h" "Element handlers"
                when "a" "See also"
                else "Unknown key"
        end
end

puts keyToName("a")
puts keyToName('a')
It gives "Unknown key" twice, instead of "See also" at least once.

Though I wonder if you're not better of with a Hash:

puts({
   "c" => "Synopsis",
   "s" => "Category",
   ...
}[key.strip])

That sounds nice, is that code faster?

Thanks for your help

···

--
"May the source be with you"

5

Aquila wrote:

Actually the code has less duplication, this was just an example. But why
doesn't this work:
def keyToName(key)
        case key.strip
...
                when "h" "Element handlers"
                when "a" "See also"
                else "Unknown key"
        end
end

puts keyToName("a")
puts keyToName('a')
It gives "Unknown key" twice, instead of "See also" at least once.

Hah, I knew that you weren't supposed to use when like that. You're actually doing this with the above code:

case key.strip
   when "hElement handlers"
   when "aSee also"
   else "Unknown key"
end

Which of course isn't what you want. Put a "then" or ":" between the condition and the action parts and it will work.

Though I wonder if you're not better of with a Hash:

puts({
  "c" => "Synopsis",
  "s" => "Category",
  ...
}[key.strip])

That sounds nice, is that code faster?

It ought to be faster, especially when you assign the Hash to a constant, but I doubt that it will matter much.