From: John Feminella <johnf@...>
Date: 2011-07-25T19:44:03+09:00
Subject: Re: Please give simple example of when to use symbols

> When do you normally use a symbol instead of a string?

If the exact sequence of characters is what's important, use a String.
If the identity is what's important, use a Symbol.

Here are some examples:

1.) A person's name should be a String, because the sequence of
characters is important.

    names = "John Paul Jones".split
    puts "first name is: #{names.first}"

2.) A status flag should be a Symbol, because the identity is what's
important. The actual name is immaterial (although of course you want
to pick a readable name that makes sense).

    missile.fire!
    puts "jammed!" if missile.status == :launch_failure

3.) When referring to other program constructs, you should almost
always use Symbols.

    obj.send(:some_method)

4.) The same rules apply when deciding whether to use Symbol or String
keys for a Hash. For instance, you'd probably have:

    phonetic_pronunciations = {"pneumonia" => "new moan ya", ...}

but you'd also have:

    colors = {:red => [255, 0, 0], :green => [0, 255, 0], :yellow =>
[255, 255, 0], ...}

~ jf
--
John Feminella
Principal Consultant, BitsBuilder
LI: http://www.linkedin.com/in/johnxf
SO: http://stackoverflow.com/users/75170/



On Mon, Jul 25, 2011 at 03:20, Kaye Ng <sbstn26@yahoo.com> wrote:
> I'm still a bit confused on whether to use strings or symbols in certain
> situations.  They produce the same results, although strings take up
> more memory, which I'm not sure how or why exactly.
>
> current_situation = "good"
> puts "Everything is fine" if current_situation == "good"
> puts "PANIC!" if current_situation == "bad"
>
> "good" and "good" and "bad" (3 strings) take up memory.  Why is that?
> Isn't the second "good"  same as the first?
>
> When do you normally use a symbol instead of a string?
>
> Thanks guys!
>
> --
> Posted via http://www.ruby-forum.com/.
>
>