Ruby: Insert Multiple Values Into String - ruby

Question

Suppose we have the string "aaabbbccc" and want to use the String#insert to convert the string to "aaa<strong>bbb</strong>ccc". Is this the best way to insert multiple values into a Ruby string using String#insert or can multiple values simultaneously be added:
string = "aaabbbccc"
opening_tag = '<strong>'
opening_index = 3
closing_tag = '</strong>'
closing_index = 6
string.insert(opening_index, opening_tag)
closing_index = 6 + opening_tag.length # I don't really like this
string.insert(closing_index, closing_tag)
Is there a way to simultaneously insert multiple substrings into a Ruby string so the closing tag does not need to be offset by the length of the first substring that is added? I would like something like this one liner:
string.insert(3 => '<strong>', 6 => '</strong>') # => "aaa<strong>bbb</strong>ccc"

Answer 1

Let's have some fun. How about
class String
def splice h
self.each_char.with_index.inject('') do |accum,(c,i)|
accum + h.fetch(i,'') + c
end
end
end
"aaabbbccc".splice(3=>"<strong>", 6=>"</strong>")
=> "aaa<strong>bbb</strong>ccc"
(you can encapsulate this however you want, I just like messing with built-ins because Ruby lets me)

Answer 2

How about inserting from right to left?
string = "aaabbbccc"
string.insert(6, '</strong>')
string.insert(3, '<strong>')
string # => "aaa<strong>bbb</strong>ccc"

Answer 3

opening_tag = '<strong>'
opening_index = 3
closing_tag = '</strong>'
closing_index = 6
string = "aaabbbccc"
string[opening_index...closing_index] =
opening_tag + string[opening_index...closing_index] + closing_tag
#=> "<strong>bbb</strong>"
string
#=> "aaa<strong>bbb</strong>ccc"

Answer 4

If your string is comprised of three groups of consecutive characters, and you'd like to insert the opening tag between the first two groups and the closing tag between the last two groups, regardless of the size of each group, you could do that like this:
def stuff_tags(str, tag)
str.scan(/((.)\2*)/)
.map(&:first)
.insert( 1, "<#{tag}>")
.insert(-2, "<\/#{tag}>")
.join
end
stuff_tags('aaabbbccc', 'strong') #=> "aaa<strong>bbb</strong>ccc"
stuff_tags('aabbbbcccccc', 'weak') #=> "aa<weak>bbbb</weak>cccccc"
I will explain the regex used by scan, but first would like to show how the calculations proceed for the string 'aaabbbccc':
a = 'aaabbbccc'.scan(/((.)\2*)/)
#=> [["aaa", "a"], ["bbb", "b"], ["ccc", "c"]]
b = a.map(&:first)
#=> ["aaa", "bbb", "ccc"]
c = b.insert( 1, "<strong>")
#=> ["aaa", "<strong>", "bbb", "ccc"]
d = c.insert(-2, "<\/strong>")
#=> ["aaa", "<strong>", "bbb", "</strong>", "ccc"]
d.join
#=> "aaa<strong>bbb</strong>ccc"
We need two capture groups in the regex. The first (having the first left parenthesis) captures the string we want. The second captures the first character, (.). This is needed so that we can require that it be followed by zero or more copies of that character, \2*.
Here's another way this can be done:
def stuff_tags(str, tag)
str.chars.chunk {|c| c}
.map {|_,a| a.join}
.insert( 1, "<#{tag}>")
.insert(-2, "<\/#{tag}>")
.join
end
The calculations of a and b above change to the following:
a = 'aaabbbccc'.chars.chunk {|c| c}
#=> #<Enumerator: #<Enumerator::Generator:0x000001021622d8>:each>
# a.to_a => [["a",["a","a","a"]],["b",["b","b","b"]],["c",["c","c","c"]]]
b = a.map {|_,a| a.join }
#=> ["aaa", "bbb", "ccc"]