Add Params Includes Submission Button Info as a rails til.

README.md

@@ -157,6 +157,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Creating Records of Has_One Associations](rails/creating-records-of-has-one-associations.md)
 - [Hash Slicing](rails/hash-slicing.md)
 - [Ignore Poltergeist JavaScript Errors](rails/ignore-poltergeist-javascript-errors.md)
+- [Params Includes Submission Button Info](rails/params-includes-submission-button-info.md)
 - [Pretend Generations](rails/pretend-generations.md)
 - [Retrieve An Object If It Exists](rails/retrieve-an-object-if-it-exists.md)
 - [Select Value For SQL Counts](rails/select-value-for-sql-counts.md)

rails/params-includes-submission-button-info.md

@@ -0,0 +1,26 @@
+# Params Includes Submission Button Info
+
+When a form is submitted for a Rails app, the respective controller action
+will have access to a variety of information in the `params` hash. Included
+is an entry with the name and value of the button that submitted the form.
+By default, Rails will give the name `commit` to a submission button.
+
+```
+<%= f.submit %>
+# results in:
+<input type="submit" name="commit" value="Submit">Submit</input>
+```
+
+The corresponding `create` action will have parameters that include that
+submission button's info:
+
+```ruby
+# in create action
+> params['commit']
+=> 'Submit'
+```
+
+This is useful when you have multiple buttons that submit the same form, but
+should have slightly different results in the corresponding action.
+Differentiating becomes easy when you can easily check which was used to
+submit the form. No javascript required.