Ruby Help

[DaveyBoy]

Hi all

Needing some help if one of you Ruby experts could assist.

I have a hash that I need to change:


I've been Googling this for two days now to no avail, so I thought I'd ask here

In order to get the result I want I have to call a definition and change it, surely it must be possible to get the result in one definition... its self explanatory if you care to have a look:

Code: Select all

@my_hash = { 0 =>"Piano", 1 =>"Guitar", 5 =>"Flute" }

def my_1st_attempt   
   (0..6).map {|n| a = @my_hash.fetch(n,"- - -");Hash[n,a]}
end

def result_that_i_want
   my_1st_attempt.reduce Hash.new, :merge
end

watch "my_1st_attempt", my_1st_attempt

watch "result_that_i_want", result_that_i_want


Hope someone can help

PS sorry for the blurred pic . . . Had to resize it

[KG_is_back]

basically what you want to do is to add element to a hash if it doesn't already exist. There are several ways to do this:

Code: Select all

#version 1
(0..6).each{|n|
@my_hash[n] = @my_hash[n] || "- - -" #if fetched element is nil, puts "- - -" in its place
}

#version 2
(0..6).each{|n|
if not(@my_hash.has_key?(n)) #if given key is not present in hash
@my_hash[n] = "- - -" #put new element in that place
end

#version 3
#this version adds default element to the hash, which is returned by default unless specific value is specified
#this is different from your expected output, but it might be what you actually want.
@my_hash.default="- - -"
@my_hash[1] #returns "Guitar"
@my_hash[2] #returns "- - -" because key 2 is not present in the hash

}



[DaveyBoy]

Hi KG

Thanks for the quick reply
Yep... that did the trick. I had to play about with it to get it to do what I want it to do but I got there in the end thanks to your help



I am auto-generating blank lines in a list and this does the job perfectly.

Thanks again KG