Ruby provides a mechanism for tapping into the program at runtime to determine the list of defined local and global variables. Ruby provides two methods to get all declared variables in a local or global scope.
Kernel#local_variables
The local_variables is available globally in your ruby programmes.
x = 5 puts local_variables # => [:x] the local_variables method will get the variables in the current local scope. So, for something like
y = 6 def do_something x = 5 puts local_variables end do_something local_variables The first line printed to the console will be the local variables inside do_something. The second print will be the local variables in the current scope, namely y.
Kernel#global_variables
In Ruby, a global variables is a variable that starts with a dollar sign $. Ruby has a set of built-in globals available for us already.
puts global_variables You can add to the list of global variables by creating your own global variables, tho you might not want to do that.
$my_global_variable = "Custom global" global_variables.find { |glob| glob == :$my_global_variable } # => :$my_global_variable Notice: All variables are stored as a Symbol.
Bonus content, the _ local variable in irb sessions.
When you launch an irb session and log the local_variables you get an _ in the list. The _ provides a way to access the last return value in case it's lost forever.
You can access the return value of the previous line by using _ in your irb sessions.
x = 5 y = _ puts x puts y Running this through irb you get 5 logged two times. That is because _ stores the last return value, which is the assignment of 5 to the variable x.
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