41 lines
1.4 KiB
Markdown
41 lines
1.4 KiB
Markdown
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---
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title: "Rails Snippet: Caching expensive calls"
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kind: article
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slug: rails-snippet-caching-expensive-calls
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created_at: 2008-04-09
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tags:
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- General
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- RubyOnRails
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- Ruby
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- Rails
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- snippet
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---
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In Rails, from time to time, you may encounter you have a method you call several times, but which returns always the same result. For example, have the following:
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<pre lang="ruby">class Person < ActiveRecord::Base
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has_many :articles
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def get_approved_articles
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self.articles.find(:all, :conditions => {:approved => true}, :order => 'approved_on DESC')
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end
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end</pre>
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A query is fired every time you call Person#get_approved_articles. To cache the result of the query during this request, just add a bit of magic
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<pre lang="ruby">class Person < ActiveRecord::Base
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has_many :articles
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def get_approved_articles
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@approved_articles ||= self.articles.find(:all, :conditions => {:approved => true}, :order => 'approved_on DESC')
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end
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end</pre>
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This will return the @approved_articles value if it exists. If it doesn't, which is the first time you access the method, the query is run and stored in @approved_articles for later use.
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Note: I know it's much easier to define this kind of behaviour, but it's just an illustration.
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<pre lang="ruby">class Person < ActiveRecord::Base
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has_many :articles
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has_many :approved_articles, :class_name => "Article", :conditions => {:approved => true}, :order => 'approved_on DESC'
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end</pre>
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