Welcome to our hands-on tutorial on data filtering in Ruby.

Filtering is a fundamental skill in programming that lets us focus on specific data we care about while discarding the rest. By filtering, we can extract only the data that meets certain criteria, making it easier to work with relevant information.

Data filtering in programming is similar to filtering options on a shopping website. Imagine you’re looking for a specific shirt online. You can filter by color, size, brand, and other attributes. In programming, our data items are like those shirts, and our filtering criteria serve as conditions that decide which items pass through.

Loops allow us to repeat actions on each element in a data stream, making them useful for filtering. In Ruby, we can use the each loop to examine each element against certain criteria.

For instance, let’s filter out numbers less than ten from an array:

Ruby
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1def filter_with_loops(data_stream)
2  filtered_data = []
3  data_stream.each do |item|
4    filtered_data << item if item < 10
5  end
6  filtered_data
7end

In this example, the each loop checks each item, and if it’s less than ten, it adds it to the filtered_data array.

Ruby provides a select method specifically for filtering. With select, we can pass a condition block to filter elements in a simpler and more readable way.

Here’s how we could rewrite the previous example using select:

Ruby
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1def filter_with_select(data_stream)
2  data_stream.select { |item| item < 10 }
3end

Here, { |item| item < 10 } is the condition that select uses to filter elements in data_stream.

In some cases, you may want to filter elements based on more than one condition. In Ruby, we can use && (AND) and || (OR) to combine conditions.

For example, let’s filter for numbers that are both less than ten and even:

Ruby
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1data_stream = [23, 5, 7, 12, 19, 2]
2
3filtered_data = data_stream.select { |item| item < 10 && item.even? }
4puts filtered_data # Output: [2]

In this example, only the numbers that are both less than ten and even pass through the filter.

Alternatively, let’s say we want numbers that are either less than ten or greater than twenty:

Ruby
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1filtered_data = data_stream.select { |item| item < 10 || item > 20 }
2puts filtered_data # Output: [5, 7, 2, 23]

Here, numbers satisfying either condition (less than ten or greater than twenty) are included in the output.

Now that we understand different filtering techniques, let’s try them out with an example:

Ruby
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1data_stream = [23, 5, 7, 12, 19, 2]
2
3# Filtering with loops
4filtered_data_loops = filter_with_loops(data_stream)
5puts "Filtered data with loops: #{filtered_data_loops}" # Output: [5, 7, 2]
6
7# Filtering with select method
8filtered_data_select = filter_with_select(data_stream)
9puts "Filtered data with select method: #{filtered_data_select}" # Output: [5, 7, 2]
10
11# Filtering with combined conditions
12filtered_data_combined = data_stream.select { |item| item < 10 && item.even? }
13puts "Filtered data with combined conditions: #{filtered_data_combined}" # Output: [2]

In each case, we filter the data_stream to extract only the elements that match our criteria.

Today, we explored data filtering in Ruby using both loops and the select method, and learned how to combine conditions for more precise filtering. Filtering allows us to refine data streams to focus on the specific elements we need.

Get ready to apply these skills in the upcoming exercises. Happy coding!