What is the best way to filter an array in Ruby using `select`, `collect`, or `map`?

General Discussions
1

What is the best way to filter an array in Ruby using select, collect, or map?

I understand the syntax for mapping:

a = ["a", "b", "c", "d"]      #=> ["a", "b", "c", "d"]  
a.map { |item| "a" == item }  #=> [true, false, false, false]  
a.select { |item| "a" == item }  #=> ["a"]

But if I have an array of hashes like this:

details[1]  
=> { sku: "507772-B21", desc: "HP 1TB 3G SATA 7.2K RPM LFF (3 .", qty: "", qty2: "1", price: "5,204.34 P" }

How can I filter this array in Ruby to remove entries where qty is an empty string or select only the ones that have a value?

I tried:

details.map { |item| "" == item }

But it just returns a lot of false values. When I switch map to select, I get an empty array. What’s the correct approach to Ruby filtering in this case?

2

Using Select for Filtering: When working with an array of hashes in Ruby, select is a great way to filter out elements based on a condition.

Since you want to remove entries where qty is an empty string, you can do this:

filtered_details = details.select { |item| item[:qty] != "" }

This will return only those elements where qty is not an empty string. select is useful when you need to retain elements that meet a specific condition."

3

(Why map Doesn’t Work and Alternative Approach: You can also use map is not the right choice here because it transforms each element rather than filtering them.

details.map { |item| item[:qty] != "" } 
=> [true, false, true, false] (Returns booleans, not filtered hashes)

To achieve filtering, reject is another alternative:

filtered_details = details.reject { |item| item[:qty] == "" }

While select keeps what matches the condition, reject removes what doesn’t. Sometimes reject makes the intention clearer when you want to exclude certain values."