Check instance variable in Rails

Question

I don't understand how I must change an if (condition) to check for the presence of this variable.

<%= if (@article.location != nil) %>
<%= image_tag "http://maps.google.com/maps/api/staticmap?size=450x300&sensor=false&zoom=16&markers=#{@article.location.latitude}%2C#{@article.location.longitude}" %>
<% end %>

ahmacleod · Accepted Answer · 2015-09-17 00:19:25Z

1

Assuming that @article has a location method, one typically uses the present? method for this purpose:

<% if @article.location.present? %>
    ...
<% end %>

You can substitute nil? if you want to be more strict about it (present? returns false for an empty string, which is usually what you want).

If you're not sure that @article even has a location method, you can test for it first, using respond_to?:

<% if @article.respond_to?(:location) && @article.location.present? %>
    ...
<% end %>

answered Sep 17, 2015 at 0:19

ahmacleod

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2 Comments

Фарсук Фарсейкин Over a year ago

oh great, really helpful, can you add documentation about all like_this? methods

ahmacleod Over a year ago

They all come from different places. nil? and respond_to? are part of core ruby. present? is part of ActiveSupport. There are many such meta methods.

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