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pages/single-sourcing/conditional_logic.md

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+---
+title: Conditional logic
+permalink: /conditional_logic/
+tags: single-sourcing
+audience: writer, designer
+---
+If you want to create different outputs for different audiences, you can do all of this using a combination of Jekyll's Liquid markup and values in your configuration file.
+
+{{tip}} Definitely check out [Liquid's documentation](http://docs.shopify.com/themes/liquid-documentation/basics) for more details about how to use operators and other liquid markup. The notes here are a small, somewhat superficial sample from the site.{{end}}
+
+## Where to store filtering values
+
+You can filter content based on values that you have set either in your config file or in a file in your _data folder. If you set the attribute in your config file, you need to restart the Jekyll server to see the changes. If you set the value in a file in your _data folder, you don't need to restart the server when you make changes. 
+
+## Conditional logic based on config file value
+
+Here's an example of conditional logic based on a value in the configs/config_writer.yml file. In my config_writer.yml file, I have the following:
+
+```
+audience: writer
+```
+
+On a page in my site (it can be HTML or markdown), I can conditionalize content using the following:
+
+
+{% comment %}
+{% raw %}
+```
+{% if site.audience == "writer" %}
+The writer audience should see this...
+{% elsif site.audience == "designer" %}
+The designer audience should see this ...
+{% endif %}
+```
+ {% endraw %}
+ {% endcomment %}
+
+
+This uses simple `if-elsif` logic to determine what is shown (note the spelling of `elsif`). The `else` statement handles all other conditions not handled by the `if` statements. 
+
+Here's an example of `if-else` logic inside a list:
+
+{% raw %}
+```liquid
+To bake a casserole:
+
+1. Gather the ingredients.
+{% if site.audience == "writer" %}
+2. Add in a pound of meat.
+{% elsif site.audience == "designer" %}
+3. Add in an extra can of beans.
+{% endif %}
+3. Bake in oven for 45 min.
+```
+{% endraw %}
+
+Here's an example of using conditional logic based on a value in a data file:
+
+{% comment %}
+{% raw %}
+```
+{% if site.data.options.audience == "web" %}
+show this web content...
+{% elsif site.data.options.audience == "acme" %}
+show this acme content...
+{% else %}
+this shows if neither of the above two if conditions are met.
+{% endif %}
+```
+{% endraw %}
+{% endcomment %}
+
+Here is my _data folder I have a file called options where the audience property is stored.
+
+
+## Or operator
+
+You can use more advanced Liquid markup for conditional logic, such as an `or` command. See [Shopify's Liquid documentation](http://docs.shopify.com/themes/liquid-documentation/basics/operators) for more details. 
+
+For example, here's an example using `or`:
+
+{% raw %}
+```
+{% if site.audience contains "vegan" or site.audience == "vegetarian" %}
+    // run this.
+{% endif %}
+```
+{% endraw %}
+
+With conditional statements, you don't need the elsif or else options.
+
+## Specifying a data source
+
+You can also specify a `data_source` for your data location in your configuration file. Then you aren't limited to simply using `_data` to store your data. 
+
+For example, suppose you have 2 projects: alpha and beta. You might store all the data files for alpha inside data_alpha, and all the data files for beta inside data_beta.
+
+In your configuration file, specify the data source like this:
+
+```
+data_source: data_alpha
+```
+
+Then create a folder called data_alpha.
+
+## Conditional logic based on page namespace
+
+You can also create conditional logic based on the page namespace. For example, create a page with front matter as follows:
+
+{% raw %}
+```liquid
+---
+layout: page
+user_plan: full
+---
+```
+ {% endraw %}
+
+Now you can run logic based on the conditional property in that page's front matter:
+
+{% raw %}
+```liquid
+{% if page.user_plan` == "full" %}
+// run this code
+{% endif %}
+```
+{% endraw %}