Question

I want to do a sequence of gsubs against one string, so I utilized the fact that gsub can take a hash as the second argument. One thing I wanted to do with gsub is to convert a sequence of one or more space/tab into a single space, so I have something essentially as follows:

gsub(/[ \t]+/, {/[ \t]+/ => ' '})

In my actual code, the first argument is a union of the regexp I gave here, and the second argument includes more key-value pairs.

Now, when I apply this to a string, all of the space/tabs are deleted. I suppose this is because the match to the first argument is not regarded as matching to the key [ \t] in the second argument (hash). Does the match in the second argument hash only looks for exact string match, not regexp match? If so, is there any way to get around it?

Answer 1

This is a related question. If you need to use the hash because many things have to be substituted, this might work:

list = Hash.new{|h,k|if  /\s+/ =~ k then ' ' else k end}
list['foo'] = 'bar'
list['apple'] = 'banana'

p "appleabc\t  \tabc  apple foo".gsub(/\w+|\W+/,list)
#=> "appleabc abc banana bar"
p list
#=>{"foo"=>"bar", "apple"=>"banana"} no garbage