From: Robert Klemme <shortcutter@...>
Date: 2012-04-10T23:02:15+09:00
Subject: Re: New to Ruby, tutorial gives wrong example.

On Tue, Apr 10, 2012 at 8:55 AM, Bartosz Dziewoński <matma.rex@gmail.com> wrote:
> You can use Struct for simple classes like this. The following should
> work in the same way as your code:
>
>  Rectangle = Struct.new :y, :x, :height, :width, :linecolor,
> :fillcolor, :linewidth # note the colons
>
>  rect = Rectangle.new 10, 20, 50, 60, "blue","yellow", 99 # you need
> to pass all arguments, linewidth too - it's not optional
>  rect.linewidth = 4

That's not true: all values are optional.

irb(main):001:0> Rectangle = Struct.new :y, :x, :height, :width,
:linecolor, :fillcolor, :linewidth
=> Rectangle
irb(main):002:0> r = Rectangle.new
=> #<struct Rectangle y=nil, x=nil, height=nil, width=nil,
linecolor=nil, fillcolor=nil, linewidth=nil>
irb(main):003:0> r = Rectangle.new 10, 20, 50, 60, "blue","yellow", 99
=> #<struct Rectangle y=10, x=20, height=50, width=60,
linecolor="blue", fillcolor="yellow", linewidth=99>
irb(main):004:0> r = Rectangle.new 10, 20, 50, 60, "blue","yellow"
=> #<struct Rectangle y=10, x=20, height=50, width=60,
linecolor="blue", fillcolor="yellow", linewidth=nil>
irb(main):005:0> r.linewidth = 4
=> 4
irb(main):006:0> r
=> #<struct Rectangle y=10, x=20, height=50, width=60,
linecolor="blue", fillcolor="yellow", linewidth=4>

One can also easily define methods with Struct:

irb(main):001:0> Rectangle = Struct.new :y, :x, :height, :width,
:linecolor, :fillcolor, :linewidth do
irb(main):002:1* def paint
irb(main):003:2> puts "[]"
irb(main):004:2> end
irb(main):005:1> end
=> Rectangle
irb(main):006:0> r = Rectangle.new 10, 20, 50, 60, "blue","yellow"
=> #<struct Rectangle y=10, x=20, height=50, width=60,
linecolor="blue", fillcolor="yellow", linewidth=nil>
irb(main):007:0> r.paint
[]
=> nil

Kind regards

robert

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