insert
insert(p1, p2)Inserts other_str before the character at the given index, modifying str. Negative indices count from the end of the string, and insert after the given character. The intent is insert aString so that it starts at the given index.
"abcd".insert(0, 'X') #=> "Xabcd" "abcd".insert(3, 'X') #=> "abcXd" "abcd".insert(4, 'X') #=> "abcdX" "abcd".insert(-3, 'X') #=> "abXcd" "abcd".insert(-1, 'X') #=> "abcdX"
2Notes
Better autopad numbers
There is a much better way than to use diwadn's method if you want to pad numbers with zeros. Here's my recommended way to do it:
"Number: %010d" % 12345 #=> "Number: 0000012345"
It's very easy. First we begin our placeholder with "%", then we specify a zero (0) to signify padding with zeros. If we omitted this zero, the number would be padded with spaces instead. When we have done that, just specify the target length of the string. At last a single "d" is placed to signify that we are inserting a number.
Please see String#% and Kernel#sprintf for more information about how to do this.
Here's another example of how to do it: 12345.to_s.rjust(10, "0") #=> "0000012345"
See String#rjust for more information.
Any of these methods are a lot better than the method outlined below.
Destructive to the Original String.
Just as an FYI this function is destructive to the original String object.
name = 'draper' #=> "draper"
name.insert( 0, 'don ' ) #=> 'don draper'
name #=> 'don draper'