[Solved] Why are there three variables with `merge` method?

Question

If you read the documentation, you will learn it’s: key, old value, and new value.

h1.merge(h2) { |key, old, new| new - old }

means the final result will have value h2[key] - h1[key]. Since you are merging h2 over h1, values from h2 will be new values and those from h1 will be old values.

Accepted Answer

If you read the documentation, you will learn it’s: key, old value, and new value.

h1.merge(h2) { |key, old, new| new - old }

means the final result will have value h2[key] - h1[key]. Since you are merging h2 over h1, values from h2 will be new values and those from h1 will be old values.