Ruby provides many powerful methods for string manipulation, and among them, delete_suffix and delete_prefix are particularly useful when dealing with structured text. These methods allow you to remove a specified suffix or prefix from a string if it exists, providing a clean and efficient way to handle text processing.
Basic Usage
The delete_suffix and delete_prefix methods help eliminate unwanted leading or trailing parts of a string without requiring complex regular expressions.
delete_suffix
The delete_suffix method removes a given suffix from the string if it ends with that suffix. If the string does not contain the suffix, it remains unchanged.
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filename = "report_2025.pdf"
clean_name = filename.delete_suffix(".pdf")
puts clean_name # Output: "report_2025"
delete_prefix
Similarly, delete_prefix removes a given prefix from a string if it starts with it. If the prefix is not found, the string remains unchanged.
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url = "https://example.com"
domain = url.delete_prefix("https://")
puts domain # Output: "example.com"
Advanced Use Cases
Removing Multiple Prefixes or Suffixes
Sometimes, you may need to remove multiple possible prefixes or suffixes. This can be done using an array and chaining method calls.
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prefixes = ["Mr. ", "Mrs. ", "Dr. "]
name = "Dr. Alice"
clean_name = prefixes.reduce(name) { |str, prefix| str.delete_prefix(prefix) }
puts clean_name # Output: "Alice"
Alternative for Suffixes:
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suffixes = [".jpg", ".png", ".gif"]
file = "image.png"
clean_file = suffixes.reduce(file) { |str, suffix| str.delete_suffix(suffix) }
puts clean_file # Output: "image"
Using in File Processing
When working with filenames, delete_suffix is particularly useful for removing extensions before renaming or organizing files.
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files = ["document.docx", "photo.jpg", "script.rb"]
clean_files = files.map { |file| file.delete_suffix(File.extname(file)) }
puts clean_files # Output: ["document", "photo", "script"]
Performance Considerations
Unlike regular expressions, delete_suffix and delete_prefix are optimized for direct string comparisons, making them faster and more efficient for simple prefix/suffix removal.
Benchmarking
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require 'benchmark'
str = "example_string_suffix"
suffix = "_suffix"
Benchmark.bm do |x|
x.report("delete_suffix") { 100_000.times { str.delete_suffix(suffix) } }
x.report("gsub") { 100_000.times { str.gsub(/_suffix$/, '') } }
end
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user system total real
delete_suffix 0.031387 0.000139 0.031526 ( 0.031533)
gsub 0.227606 0.001095 0.228701 ( 0.229052)
delete_suffix is generally faster than gsub for removing static suffixes since it avoids regex overhead.
The delete_suffix and delete_prefix methods in Ruby provide a simple yet powerful way to manipulate strings efficiently. They are excellent alternatives to gsub or regex-based solutions when dealing with structured text. Whether cleaning filenames, processing user input, or handling URLs, these methods offer an elegant and performant approach.