{"id":878,"date":"2026-01-30T09:55:28","date_gmt":"2026-01-30T09:55:28","guid":{"rendered":"https:\/\/productive.io\/engineering\/?p=878"},"modified":"2026-01-30T09:55:28","modified_gmt":"2026-01-30T09:55:28","slug":"watch-out-when-overriding-memoized-methods","status":"publish","type":"post","link":"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/","title":{"rendered":"Watch Out When Overriding Memoized Methods"},"content":{"rendered":"

Backend<\/a><\/p> –

{{minutes}} min read<\/p>

Watch Out When Overriding Memoized Methods<\/h1> \"\" <\/a>

Nikola Buhini\u010dek<\/p><\/a> Backend Tech Lead at Productive. Pretty passionate about working on one product and taking part in decision-making. When I\u2019m not coding, you\u2019ll probably find me chilling with my friends and family.

January 30, 2026<\/p> <\/a> <\/a> <\/a> \"\"

<\/p>

This post was inspired by a bug that was caused by not thinking ahead when overriding a memoized method. Once we noticed the buggy behaviour, it took me some\u00a0binding.pry<\/em>\u00a0time to figure out what was going on.

Lets check out what happened.<\/p> \"\"

A simple\u00a0Ruby<\/strong>\u00a0class which is the base class for the specific actions we need to implement for our\u00a0Rails app<\/strong>.

The action for which we figured out the bug was the action of creating comments on various objects. This is what the code looks like:<\/p> \"\"

Not much code is actually shown but just enough to spot the bug. Found it?<\/p>

What Was Going On?<\/strong><\/h2>

Basically what was happening when running\u00a0CreateComment#execute_action<\/code>\u00a0was the following:

In the\u00a0execute_action<\/code>\u00a0we firstly need to interpolate some attributes – defined by the specific action class. In this case, for the\u00a0CreateComment<\/code>\u00a0action that was only the\u00a0'body'<\/code>\u00a0attribute.<\/p> \"\"

That’s fine – we do some logic, the\u00a0'body'<\/code>\u00a0attribute gets interpolated and that value is set as the new value for the\u00a0'body'<\/code>\u00a0key in the form_attributes hash.<\/p> \"\"

But, as the implementation of the\u00a0CreateComment<\/code>\u00a0class uses\u00a0super.merge(...)<\/code>\u00a0what we get is actually a new hash each time the method is called.<\/p> \"\"

The next time, after the interpolation is over, the method\u00a0form_attributes<\/code>\u00a0is called when passing that hash to our form object and in that moment, the form object gets a newly generated hash that doesn’t have the interpolated\u00a0'body'<\/code>\u00a0value. So the interpolation was actually pointless as would any other modification of the\u00a0form_attributes<\/code>\u00a0hash prior to the\u00a0form.process<\/code>\u00a0call be.<\/p>

The Solution<\/strong><\/h2> \"\"

Added memoization to the\u00a0CreateComment#form_attributes<\/code>\u00a0method.

Simple as that and when you think about it, also pretty obvious that it needed to look like this from the start.

p.s. These snippets maybe look a bit too simple and memoization probably looks like it’s not needed but it’s a stripped version of the real classes. The\u00a0form_attributes<\/code>\u00a0method is called and modified quite a few times<\/em>.<\/p> <\/a> <\/a> <\/a> \"\"

Nikola Buhini\u010dek<\/p> Backend Tech Lead at Productive. Pretty passionate about working on one product and taking part in decision-making. When I\u2019m not coding, you\u2019ll probably find me chilling with my friends and family. More From This Author <\/a>

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<\/p> <\/a>","protected":false},"excerpt":{"rendered":"","protected":false},"author":40,"featured_media":891,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"es_utils_meta_schema":"","footnotes":""},"categories":[11],"tags":[],"class_list":["post-878","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-backend"],"acf":[],"yoast_head":"\nWatch Out When Overriding Memoized Methods - Building Productive<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Watch Out When Overriding Memoized Methods\" \/>\n<meta property=\"og:url\" content=\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/\" \/>\n<meta property=\"og:site_name\" content=\"Building Productive\" \/>\n<meta property=\"article:published_time\" content=\"2026-01-30T09:55:28+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/website-assets.productive.io\/uploads\/sites\/2\/2024\/01\/BLOG_2x.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1901\" \/>\n\t<meta property=\"og:image:height\" content=\"797\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Nikola Buhini\u010dek\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Nikola Buhini\u010dek\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/\"},\"author\":{\"name\":\"Nikola Buhini\u010dek\",\"@id\":\"https:\/\/productive.io\/engineering\/#\/schema\/person\/b8aea92d17640ade1fc1230b0812ae29\"},\"headline\":\"Watch Out When Overriding Memoized Methods\",\"datePublished\":\"2026-01-30T09:55:28+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/\"},\"wordCount\":6,\"commentCount\":0,\"image\":{\"@id\":\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/website-assets.productive.io\/uploads\/sites\/2\/2024\/01\/BLOG_2x.png\",\"articleSection\":[\"Backend\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/\",\"url\":\"https:\/\/productive.io\/engineering\/watch-out-when-overriding-memoized-methods\/\",\"name\":\"Watch Out When Overriding Memoized Methods - 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