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comp.lang.ruby

cgi question

Boris Glawe

6/20/2005 9:18:00 PM

Hi, the following code results in NoMethodError, when being executed as a cgi
script.

The reason is the line "+ cgi.b {"hello world in bold"}" at the bottom.

Can anybody explain me, what's happening here?
The preceding block simply returns a (html) string, containing a form, which is
concatenated with "<b>hello world in bold</b>"

Do you have any idea?


thanks Boris


#!/usr/bin/ruby

require "cgi"


cgi=CGI.new("html4")

cgi.out {

CGI.pretty(
cgi.html{
cgi.head{
cgi.title{ "testpage" }
} +
cgi.body{
cgi.form{
cgi.table( {'border' => '1'} ){
cgi.tr {
cgi.td{ "hello"} +
cgi.td {"world"}
} # end tr
} # end table
} # end form
+ cgi.b {"hello world in bold"}
} # end head
} # end html
) # end CGI#pretty

} # end cgi.out
#############################################################

the error message:

# ./test.rb
(offline mode: enter name=value pairs on standard input)
../test.rb:24: undefined method `+@' for "<B>hello world in bold</B>":String
(NoMethodError)
from ./test.rb:15:in `body'
from ./test.rb:15
from ./test.rb:11:in `html'
from /usr/lib/ruby/1.8/cgi.rb:1653:in `html'
from /usr/lib/ruby/1.8/cgi.rb:1653:in `html'
from ./test.rb:11
from ./test.rb:8:in `out'
from ./test.rb:8
3 Answers

Ryan Leavengood

6/20/2005 9:33:00 PM

0

Boris Glawe said:
> Hi, the following code results in NoMethodError, when being executed as a
> cgi
> script.
>
> The reason is the line "+ cgi.b {"hello world in bold"}" at the bottom.

You are attempting to call the unary operator + on cgi.b, which returns a
string. In Ruby's internals the unary + is actually the +@ method. This
code works:

require "cgi"

cgi=CGI.new("html4")

cgi.out {

CGI.pretty(
cgi.html{
cgi.head{
cgi.title{ "testpage" }
} +
cgi.body{
cgi.form{
cgi.table( {'border' => '1'} ){
cgi.tr {
cgi.td{ "hello"} +
cgi.td {"world"}
} # end tr
} # end table
} +# end form <--NOTE WHERE THE PLUS IS
cgi.b {"hello world in bold"}
} # end head
} # end html
) # end CGI#pretty

} # end cgi.out

Ryan

Boris Glawe

6/20/2005 9:48:00 PM

0

Ryan Leavengood wrote:
> Boris Glawe said:
>
>>Hi, the following code results in NoMethodError, when being executed as a
>>cgi
>>script.
>>
>>The reason is the line "+ cgi.b {"hello world in bold"}" at the bottom.
>
>
> You are attempting to call the unary operator + on cgi.b, which returns a
> string. In Ruby's internals the unary + is actually the +@ method. This
> code works:
>

Thanks a lot!!

This is an ugly pitfall, as ruby usually grants a lot of freedom in layout.

greets Boris

Ryan Leavengood

6/20/2005 10:11:00 PM

0

Boris Glawe said:
>
> Thanks a lot!!
>
> This is an ugly pitfall, as ruby usually grants a lot of freedom in
> layout.

I agree that in most cases Ruby grants a lot of freedom, but I don't think
this is too ugly of a pitfall. There needs to some way of indicating
positive and negative numbers, and Ruby just makes things more flexible by
making that a method. You can make your own classes that use it:

class Book
attr_reader :name, :good
def initialize(name)
@name = name
@good = nil
end

def +@
@good = true
end

def -@
@good = false
end

def to_s
"#@name is #{@good == nil ? 'unrated' : @good ? 'good' : 'bad'}"
end
end

book = Book.new('Da Vinci Code')
puts book
+book
puts book
-book
puts book
__END__

Output:
Da Vinci Code is unrated
Da Vinci Code is good
Da Vinci Code is bad


Though it may not be all that useful in most cases.

Ryan