Find and replace variable in Ruby string

Question

Let's say I have a string like so:

"Lorem ipsum de color [post]57[/post] sit amet [post]103[/post] desectator."

I want to find all occurrences of [post]*[/post] and replace it with the title of the post represented by the number. I'd end up with something like so:

"Lorem ipsum de color Angry Turtle sit amet Fuzzy Rabit desectator."

I'm guessing a regex will be needed... looking for what the regex would be and how to use.

By the way, if there's a syntax for my post id variables that would make this easier, that's totally cool too. — tybro0103
– tybro0103, Commented Oct 29, 2010 at 20:56
If your string really has only one level of one kind of markup, then you could parse it awkwardly (by rescanning) using a regex. But in general, see: stackoverflow.com/questions/1732348/… — DigitalRoss
– DigitalRoss, Commented Oct 29, 2010 at 21:06

jwarchol · Accepted Answer · 2010-10-29 21:11:21Z

7

The gsub method on String has a handy block variation that works well here:

>> s = "Lorem ipsum de color [post]57[/post] sit amet [post]103[/post] desectator."
=> "Lorem ipsum de color [post]57[/post] sit amet [post]103[/post] desectator."

>> posts = {"57" => "Angry Turtle", "103" => "Fuzzy Rabit"}
=> {"57"=>"Angry Turtle", "103"=>"Fuzzy Rabit"}

>> s.gsub(/\[post\](\d+)\[\/post\]/) {|m| posts[$1] }
=> "Lorem ipsum de color Angry Turtle sit amet Fuzzy Rabit desectator."

Your syntax couldn't be much less regex friendly though. Try not to use brackets and slashes.

answered Oct 29, 2010 at 21:11

jwarchol

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2 Comments

tybro0103 Over a year ago

cool thanks... what kind of syntax would you recommend for such a thing?

jwarchol Over a year ago

Anything that doesn't need to be escaped in the regexp and does't occur elsewhere in your normal text is a good bet. Some template languages use curly braces { } or double curly braces {{ }}.

steenslag · Accepted Answer · 2010-10-29 22:13:25Z

2

(after reading your easier syntax comment) If you have a hash like

posts = {57 => "Angry Turtle", 103 => "Fuzzy Rabit"}

or an array like, ehm,

posts = []
posts[57] = "Angry Turtle"
posts[103] = "Fuzzy Rabbit"

then why not go for string interpolation?

"Lorem ipsum de color #{posts[57]} sit amet #{posts[103]} desectator."

And you're ready to go.

edited Oct 29, 2010 at 22:13

answered Oct 29, 2010 at 21:41

steenslag

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1 Comment

tybro0103 Over a year ago

Well my string is going to be input by a user. Plus my logic to get the post title won't be that direct.

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