Question

In Ruby you can reference variables inside strings and they are interpolated at runtime.

For example if you declare a variable foo equals 'Ted' and you declare a string 'Hello, #{foo}' it interpolates to 'Hello, Ted'.

I’ve not been able to figure out how to perform the magic '#{}' interpolation on data read from a file.

In pseudo code it might look something like this:

interpolated_string = File.new('myfile.txt').read.interpolate 

But that last interpolate method doesn’t exist.

Answer 1

Instead of interpolating, you could use erb. This blog gives simple example of ERB usage,

require 'erb' name = 'Rasmus' template_string = 'My name is <%= name %>' template = ERB.new template_string puts template.result # prints 'My name is Rasmus' 

Kernel#eval could be used, too. But most of the time you want to use a simple template system like erb.