How do I eval multiple lines of code in ruby?

Question

eval('puts "ff"\nputs "ff"')

I tried to use two expressions in one eval but it doesn't execute?

How do I do this? I want to know because I want to dynamically execute partial code.

score 7 · Answer 1 · answered Nov 03 '10 at 21:42

7

With heredoc syntax. File and line number are passed to give reference information in back traces.

eval(<<-CODE, __FILE__, __LINE__ +1 )
  some(:ruby);
  code
  # and comments
CODE

answered Nov 03 '10 at 21:42

balu

This should be the accepted answer - it works better for large multiline statements and facilitates debugging. Nice one! – Steven Garcia Jan 07 '13 at 19:49

score 5 · Answer 2 · answered Nov 03 '10 at 06:26

5

eval("puts 'ff'\nputs 'ff'")

also works. '\n' gets treated as literally a slash and an n, because single quotes work differently to double quotes.

answered Nov 03 '10 at 06:26

Andrew Grimm

Really? Would appreciate if you could point to some documentation? I thought that interchanging quotes didn't really matter ? – Zabba Nov 03 '10 at 06:34
@Zabba: You can try it in irb, or you can look at documentation mentioned at [Backslashes in Single quoted strings vs. Double quoted strings in Ruby?](http://stackoverflow.com/questions/648156/backslashes-in-single-quoted-strings-vs-double-quoted-strings-in-ruby) – Andrew Grimm Nov 03 '10 at 06:48

score 3 · Answer 3 · answered Nov 03 '10 at 21:33

3

I use this:

eval %{
  puts 'ff'
  puts 'hello'
}

answered Nov 03 '10 at 21:33

horseyguy

score 2 · Accepted Answer · answered Nov 03 '10 at 04:27

2

Do:

eval('puts "ff";puts "ff"')

answered Nov 03 '10 at 04:27

Zabba

4 Answers4