Скачать или смотреть Converting User Input: How to Change String Representation to Decimal in Ruby on Rails

Discover how to effectively manage user input in Ruby on Rails by converting string values to decimal formats before saving them to the database.
---
This video is based on the question https://stackoverflow.com/q/64395179/ asked by the user 'Chris' ( https://stackoverflow.com/u/2922058/ ) and on the answer https://stackoverflow.com/a/64395289/ provided by the user 'Sergio Tulentsev' ( https://stackoverflow.com/u/125816/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Change user input from view before saving in model

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Converting User Input: Transforming String Representation to Decimal in Ruby on Rails

When developing applications using Ruby on Rails, it's common to encounter situations where user input does not align with the expected data format of a model. One example of this is when a user inputs time in a human-readable format, such as "1:15:15" (representing 1 hour, 15 minutes, and 15 seconds), but your model expects a numerical representation (like total seconds). This article dives into a practical solution that retains user input integrity while seamlessly converting it to a suitable format for storage.

Understanding the Problem

In Ruby on Rails applications, data types in the model can automatically cast user inputs based on their type. For instance, if a user submits the string "1:15:15," Rails may interpret and convert only the first value (1) into a decimal, disregarding the rest of the string. Consequently, when trying to use split to separate the string into hours, minutes, and seconds, it fails, leading to unexpected behaviors.

The primary challenge here is to allow users to input their time in a string format while still saving it as a decimal (total seconds) in the database. Changing the database to save strings would work, but it burdens future calculations, such as adding up total time entries, making the approach less than ideal.

The Solution: Using a Transient Accessor

To effectively tackle this problem, we can employ a technique called a transient accessor. By creating a new attribute in the model that holds the raw user input, we can ensure that Rails does not automatically cast the value before we process it. Here’s how you can achieve this:

Step 1: Modify the Model

First, we need to add a transient accessor for the runtime_string attribute in the LogEntry model. This will allow us to store the raw input from the user without any automatic type casting.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Update the Form

In your form view, you will need to replace the conventional attribute used for runtime with the new runtime_string attribute. This change ensures that the user's input goes into runtime_string, bypassing any unwanted type conversion.

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

attr_accessor: This line creates a getter and setter for the runtime_string attribute that can be used to store user input as a string.

before_save callback: This callback triggers the convert_runtime method, which converts the string input into seconds for storage when the record is saved.

split(':'): This method divides the runtime_string based on colons, yielding an array where the first element represents hours, the second minutes, and the third seconds.

Calculating Total Seconds: The conversion formula a[0].to_f * 3600 + a[1].to_f * 60 + a[2].to_f computes the total seconds from the user-friendly string format.

Conclusion

Using a transient accessor provides a flexible way to handle user input while allowing you to retain the integrity of your data model. This solution is particularly useful for managing time inputs but can be adapted to various scenarios where user data needs to be processed before saving to the database. By following these steps, you can ensure a seamless experience for users while keeping your data organized and ready for calculations.

Applying this approach not only solves your immediate issue but also enhances the maintainability and usability of your application in the long run.