Phoenix: Templates Are Just Functions

The author describes confusion about why Phoenix separates views and templates, especially after seeing a template call a function from the view and pass @conn into it. Chris McCord explains that templates are compiled into functions injected into the view module at compile time.

After testing a custom render/2 function, the author sees that a view can render without a template and that different templates can be selected by pattern matching. This makes the request flow easier to picture and removes part of the sense that Phoenix rendering is magical.

Reading notes

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• The author read the Phoenix Guides expecting a more familiar view-template setup and became confused at the Views and Templates guides.
• In the example, handler_info/1 lives in the view, and the template calls it with @conn.
• Chris McCord explains that templates are compiled down to functions and injected into the view at compile time.
• A custom render("foo.html", _assigns) function in HelloPhoenix.PageView returns "Foo!" without a template file.
• The author confirms that render/2 can call handler_info(assigns.conn) directly from the view.
• The same render/2 function can pattern match on the template name and return different output for "foo.html" and "foobar.html".
• The author concludes that understanding templates as injected render functions makes Phoenix rendering feel less like magic and easier to reason about.