Ruby Split String Examples

Call the split method to separate strings. Use string and regular expression delimiters.

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Split. Strings often contain blocks of data. With split, we separate these blocks based on a delimiter. In Ruby, a string, or a regular expression, is used as the separator.

Split details. This method is widely used. When we omit an argument, it separates a string on spaces. This is the default behavior.

First example. Consider the input string here: it contains 3 parts. Each one is separated with a comma character—and there are internal spaces in each part.
First: We call split(), specifying a comma as the delimiter character. This separates those 3 parts.
And: The resulting array has 3 string elements. We loop over these with the "each" iterator.
Ruby program that uses split # Split this string on comma characters. input = "lowercase a,uppercase A,lowercase z" values = input.split(",") # Display each value to the console. values.each do |value| puts value end Output lowercase a uppercase A lowercase z

No arguments. No arguments are required to split on a space character. The space delimiter is implicit: you do not need to specify it. This can make some programs easier to read.
But: Perhaps a comment would help in this case. Usually split() is called with a delimiter, so this may not be as expected.
Ruby program that uses split, no arguments input = "a b c" # We do not specify an argument: space is implicit. values = input.split() puts values Output a b c

Regexp. Split does not require a simple string argument. It can act also upon a regular expression (regexp). In Ruby we specify these with forward slashes.
Here: We specify a delimiter of one or more non-word characters. The Kleene closure + indicates "one or more."
Tip: The delimiter here matches one or two characters. It includes both the comma and the following space.
So: The resulting string array has no empty values. It contains just the four words stored within the text.
Ruby program that uses Regexp to split value = "one, two three: four" # Split on one or more non-word characters. a = value.split(/\W+/) # Display result. puts a Output one two three four Regexp pattern \W+ One or more non-word characters.

Limit. This is the maximum number of array elements that are returned. If more elements are found than are allowed by the limit, the excess ones are grouped in the final array element.
Tip: Limiting the number of array elements can be useful if you only need the first several parts from a string.
Ruby program that splits with limit # Contains five vegetable names. value = "carrot,squash,corn,broccoli,spinach" # Split with limit of 3. vegetables = value.split(",", 3) puts vegetables Output carrot squash corn,broccoli,spinach

Empty. Often the split method will return empty entries. These are caused by having two delimiters with no interior content. We can invoke delete_if to remove these empty elements.
So: We use an iterator block. We delete all elements that are zero chars. The empty entry, between "cat" and "dog," is removed.
Ruby program that removes empty entries # Split on a comma. value = "cat,,dog,bird" elements = value.split(",") print elements, "\n" # Remove empty elements from the array. elements.delete_if{|e| e.length == 0} print elements Output ["cat", "", "dog", "bird"] ["cat", "dog", "bird"]

Characters. With split we can get the characters from a string. Pass an empty string literal ("") to the split method. The length of the array equals the length of the string.
Ruby program that splits characters value = "xyz 1" # Separate chars. array = value.split "" # Write length. puts array.length # Write elements. print array Output 5 ["x", "y", "z", " ", "1"]

File. Often we need to handle CSV files. We first use the IO.foreach iterator to easily loop over the lines in a text file. Each line must be chomped to remove the trailing newline.
Then: We use split() on the commas. The parts between the comma chars are returned in an array.
Output: The program writes the contents of the Array returned by split. It also prints the length of that Array.
Example file: csv.txt cat,tiger,meow,100 airplane,bird,200 tree,grove,400 sand,beach,fish,50 Ruby program that splits lines in file # Open this file (change file name for your program). IO.foreach("/files/csv.txt") do |line| # Remove trailing whitespace. line.chomp! # Split on comma. values = line.split(",") # Write results. print values.join("+") << "... " << String(values.length) << "\n" end Output cat+tiger+meow+100... 4 airplane+bird+200... 3 tree+grove+400... 3 sand+beach+fish+50... 4

Parse integers. Often we need to parse integer values that are in a CSV format. We first split the line, and then use Integer to convert each string.
Here: We display each number in the string that is equal to or greater than 200. The value 100 is not displayed.
Ruby program that uses split, parses Integers line = "100,200,300" # Split on the comma char. values = line.split(",") # Parse each number in the result array. values.each do |v| number = Integer(v) # Display number if it is greater than or equal to 200. if number >= 200 puts number end end Output 200 300

Join. This is the opposite of split. It merges together values in an array. With join and split we can parse a string, modify the values, and return the string to its original state.Join

In CSV files, input lines contain separating characters. We do not need a special parsing method to extract the inner strings. Split(), with a special delimiter, works well.

A review. We learned how to split based on a string delimiter. A regular expression offers more power. And finally we used join to combine strings in an Array.


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