Add 14: "Meeting some Locals"

Author: janlelis

source/posts/14-meeting-some-locals.html.md

@@ -0,0 +1,39 @@
+---
+title: Meeting some Locals
+date: 2015-05-14
+tags: syntax, regex
+---
+
+There are two very different ways to create local variables in Ruby. You are probably familiar with the classical way:
+
+    a, b = "$", "€"
+    a # => "$"
+    b # => "€"
+
+It is simple to understand and looks good. But Ruby would not be Ruby, if there weren"t for more obscure ways to assign variables: You could rewrite the previous example to create local variables in a more subtle way:
+
+    %r<(?'a'.)(?'b'.)>=~"$" "€"
+    a # => "$"
+    b # => "€"
+
+
+This implicit creation of local variables is not recommended, because obviously, it violates **PrOWCoFoHuNoMa** (Principle of writing code for humans, not machines).
+
+By the way, this will not work, when you swap operands:
+
+    "$" "€"=~%r<(?<a>.)(?<b>.)>
+    a # NameError: ...
+
+## One More Option
+
+There is also a third way to set local variables: binding's `local_variable_set`, but it does not really count, since you cannot introduce new variables this way:
+
+    a = nil
+    binding.local_variable_set :a, "$"
+    binding.local_variable_set :b, "€"
+    a # => "$"
+    b # NameError: ...
+
+## Resources
+- [RDoc: Regexp#=~](http://ruby-doc.org/core-2.2.2/Regexp.html#method-i-3D-7E)
+- [RDoc: Binding#local_variable_set](http://ruby-doc.org/core-2.2.2/Binding.html#method-i-local_variable_set)