Exit in a bloc DRY way


#1

I wrote this code that’s running well…
origin = false
contact.each {|c| origin = true if c.from == parameter }
nb -= 1 if origin

is there any way to write it in one line ? (exiting from the bloc when
the condition is true)
something like :
contact.each {|c| nb -= 1; exit; if c.from == parameter }

tfyl

joss


#2

Hi,

I think this should do the job
nb-=1 if contact.select{|c| c==parameter}.any?

it will return nb-1 if any contact matches parameter, or nil if none
match

cheers,
Dave


#3

Isn’t #find better than #select?

select wouldn’t break the first time a match was found, find would.
Less time, less memory.

Aur S.


#4

A google turns up this:

In Ruby, break exits the block with value “nil”. The caller must check
after each closure call to see if the value returned was “nil”, and
break itself, if necessary. A side effect is that you can’t return
“nil” from a block without terminating the calling structure. (As it
happens, this is almost always acceptable.)

Use IRB to figure if indeed the standard methods that accept blocks do
this checking.

contact.each {|c| nb -= 1; exit; if c.from == parameter } # the
second ; is definitely wrong

Perhaps you meant:

contact.each {|c| if c.from == parameter; nb -= 1; break; end }

Well, if each is defined and the Enumerable mixin is mixed in (it
usually is), you get #find for free, so:

$ ri Enumerable#find
-------------------------------------------------------- Enumerable#f
ind
enum.detect(ifnone = nil) {| obj | block } => obj or nil
enum.find(ifnone = nil) {| obj | block } => obj or nil


 Passes each entry in _enum_ to _block_. Returns the first for wh

ich
block is not +false+. If no object matches, calls ifnone and
returns its result when it is specified, or returns +nil+

    (1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
    (1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35

So how about:

nb = -1 if contact.find{|c| c.from == parameter }

?

This seems good.

Plug: Have a look at the adopt-a-newbie thread

Aur S.


#5

On 2/18/07, SonOfLilit removed_email_address@domain.invalid wrote:

cheers,
Dave
Isn’t #find better than #select?

select wouldn’t break the first time a match was found, find would.
Less time, less memory.

Aur S.

I’d do:

nb-=1 if contact.any?{|c| c.from==parameter}

Regards,
George.


#6

Isn’t #find better than #select?

Yes, I think you are correct.
I am learning too and had not come across find before. Thankyou for
the information.

Cheers,
Dave


#7

On 2/18/07, George O. removed_email_address@domain.invalid wrote:

I’d do:

nb-=1 if contact.any?{|c| c.from==parameter}

Regards,
George.

Wow, #any? can do this? Thanks for teaching me a cool idiom!

On 2/18/07, Sharon P. removed_email_address@domain.invalid wrote:

Yes, I think you are correct.
I am learning too and had not come across find before. Thankyou for
the information.

Cheers,
Dave

Then let me repeat that plug: Check out the adopt-a-newbie thread please
:slight_smile:

Aur S.


#8

On 2007-02-18 13:05:29 +0100, SonOfLilit removed_email_address@domain.invalid said:

$ ri Enumerable#find

       contact.each {|c|  origin = true  if c.from == parameter }
       nb -= 1 if origin

is there any way to write it in one line ? (exiting from the bloc when
the condition is true)
something like :
contact.each {|c| nb -= 1; exit; if c.from == parameter }

tfyl

joss

thanks a lot !! I love Ruby for that… start from one point … and
logically go to the DRY way… with
Rubist help…

where is this thread ‘adopt a newbie’ … ?

joss


#9

Here in the list. How do you read the list? Myself, I’m subscribed to
it in my gmail account and have it all in a label, so for me it’s
simply in the first page.

If you can’t find it, google for ruby adopt-a-newbie.

Aur S.