Auto add numbers in Ruby?

Chris Fullmer

I've forgotten how to do this the quick way (seem like there is a method already set up nicely for what I want).

I want to take a string and add numbers to the beginning of it.

Chris
Dan
Jim
Martin
Thom

becomes

0001Chris
0002Dan
0003Jim
0004Martin
0005Thom

Seems like there is a method I can use that does this automatically and smoothly for me, where I should be able to specify the amount of placeholders to use (in the example I show 4 10's places being held). Anyone recall what I'm thinking of? Just hte method is enough, I can look up its syntax again if you could kindly point me in the right direction. Thanks,

Chris

Jim

The easiest is to use strings and .next.

"0000".next => "0001"

Otherwise, if you use numbers you need to use printf or sprintf (aka format).

10.times { |i|
  printf "%04d\n", i
}


names = %w( Joe Mike Tim )
names.each_with_index do |name, i|
  printf "%04d%s\n" % [i, name]
end

See sprintf for details on formatting.

Chris Fullmer

Awesome, thanks Jim. It was string.next that I was trying to think of. That is all I needed, thanks again!

Chris

a = "000" 10.times do puts a a = a.next end

thomthom

Another way is: '1'.rjust(4, '0')

thomthom

You don't have to do this: a = a.next - you can instead do a.next!. Most probably that will be faster - thought not noticeable until you run many iterations.

If you did not require '0000' then you could also do:

a = '0000' 10.times{ puts a.next! }

Chris Fullmer

Ahh, good idea on the next! method. It didn't cross my mind that it might exist. I also like that rjust method. I'll look into that one too. Thanks Thom,

Chris

todd burch

@unknownuser said:

...4 10's places....

HAR HAR HAR HAR HAR!!!!!!!

Chris Fullmer

Laughing at my inability to express myself in functional english there Todd , or is there a big inside joke I missed (both equally likely).

Chris

Dan Rathbun

@jim said:


> names = %w( Joe Mike Tim )
> names.each_with_index do |name, i|
>   printf "%04d%s\n" % [i, name]
> end
>

index starts at 0, you'd need i+1 to start at 1

also.. printf "%04d%s\n" % [i, name]
is adding an extra operation eval that's not needed.
could be either:
puts "%04d%s\n" % [i+1, name]
or
printf("%04d%s\n",i+1,name)

Dan Rathbun

Of course if your wanting to build up an Array of Hash keys (or Attribute Dictionary keys,) just create an empty array first
keys=[]
then replace the puts or printf with
keys.push

todd burch

@chris fullmer said:

Laughing at my inability to express myself in functional english there Todd , or is there a big inside joke I missed (both equally likely).

Chris

The first.

Jim

@dan rathbun said:

also.. printf "%04d%s\n" % [i, name]
is adding an extra operation eval that's not needed.

Note to self: % is a method of Strings. Thanks.