From: Robert Klemme <shortcutter@...>
Date: 2011-01-12T22:21:37+09:00
Subject: Re: Case statements - Just beautification

On Wed, Jan 12, 2011 at 12:50 PM, flebber <flebber.crue@gmail.com> wrote:
> On Jan 12, 10:43 pm, flebber <flebber.c...@gmail.com> wrote:
>> I just want to clarify case statements the name after the word case is
>> this just for beautification and to help with code readability? What
>> purpose does it serve.
>>
>> So in my code its "winunit" and matz's code its "birthyear".
>>
>> # Method 1 - Confident - assign range
>> # number -> number
>> def pricerange(x)
>> puts "Enter the quoted price: "
>> x = gets.chomp
>> winalloc = case winunit
>>   when x == (1.50...2.50) then ...
>>   when x == (2.50...3.80) then ...
>>   when x == (3.80...5.50) then ...
>>   else something
>> end
>>
>> # Case expression tests ranges with ===
>> generation = case birthyear
>>              when 1946..1963: "Baby Boomer"
>>              when 1964..1976: "Generation X"
>>              when 1978..2000: "Generation Y"
>>              else nil
>>              end
>>
>> Sayth
>
> Oops edited mine to look more like Matz's
>
> def pricerange(x)
> puts "Enter the quoted price: "
> x = gets.chomp
> winalloc = case winunit
>          when x == 1.50...2.50: ...
>          when x == 2.50...3.80: ...
>          when x == 3.80...5.50: ...
>          else something
> end

This won't work they way you probably expect.  It will evaluate "x ==
..." expressions to a boolean value (true or false) and then evaluate
true|false === winunit which will only ever be true if winunit itself
is true or false.

You need to decide which of the two forms of case you want to use

1. with a single value

case x
when A
when B
when C
else
end

In this case A|B|C === x is evaluated and if it returns a trueish
value the corresponding branch will be evaluated.

2. without value

case
when D > x
when E.include? x
when its_too_late()
else
end

In this case each expression after "when" is evaluated and if it
returns a trueish value the corresponding branch will be evaluated.

Note: trueish values are all values except nil and false.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/