Скачать или смотреть How to Match and Replace Patterns without Regex in Ruby

Learn to easily match and replace patterns in Ruby without using regex with our step-by-step guide on handling variables in strings.
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Solving String Substitution without Regex in Ruby

In the world of programming, you might often face challenges involving string manipulation and pattern matching. One such challenge is substituting specific variables in a string without relying on regular expressions (regex). This question, which was recently posed in a coding interview, showcases how to tackle the problem using pure Ruby methods. Let’s delve into the solution step-by-step.

The Problem

You have a string where variables are wrapped between percentage signs (%), and you need to replace these variables with their corresponding values from a hash. The structure of the input is as follows:

String: %greet%! Hi there, %var_1% that can be any other %var_2% injected to the %var_3%. Nice!, goodbye!

Dictionary (hash in Ruby): { greet: 'Hi there', var_1: 'FIRST VARIABLE', var_2: 'values', var_3: 'string' }

Your task is to perform the substitution without using regex, making it a fun exercise in string manipulation.

The Solution Explained

Step 1: Splitting the String

The first step is to split the string into chunks based on the delimiter %. This will allow us to isolate the keys that need to be replaced. Here’s how you can achieve this:

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What happens here is that chunks will contain an array where the odd indices are the placeholder keys and the even indices are the parts of the string that do not require replacement.

Step 2: Iterating through Chunks

Next, we need to iterate through the chunks array. During this iteration, we will check the index of each chunk and decide whether to replace it with the corresponding value from the dictionary. For example, if the index is even, we keep the chunk as is, but if it’s odd, we replace it.

Here’s the code for this step:

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

Step 3: Joining the Chunks

Finally, after all replacements are made, we will join the chunks back together to form the final string. The join method will concatenate the elements of the array back into a single string.

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The expected output will be:

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

Important Note

This method does not handle malformed input or cases where the expected keys are missing from the dictionary. It's always wise to include error handling when dealing with string manipulation in production code.

Conclusion

In this guide, we explored a straightforward approach to replace variable patterns in a string using Ruby, without falling back on regex. By effectively splitting, iterating, and joining the components of the string, we achieved the desired substitution. This method reinforces the idea that sometimes the simplest solutions can also be the most effective.

If you found this guide helpful, consider practicing more string manipulation techniques to enhance your programming skillset!