Given nested hashes, which style guide compliant Ruby code flattens keys into a single-level hash with combined keys separated by underscores?

hard📝 Application Q9 of 15

Ruby - Ecosystem and Best Practices

Anested = {a: {b: 1}} flat = nested.flatten

Bnested = {a: {b: 1}} flat = {} nested.each { |k,v| v.each { |k2,v2| flat["#{k}_#{k2}"] = v2 } }

Cnested = {a: {b: 1}} flat = nested.map { |k,v| [k, v] }.to_h

Dnested = {a: {b: 1}} flat = nested.reduce({}) { |h,(k,v)| h.merge(v) }

Step-by-Step Solution

Solution:

Step 1: Understand flattening nested hashes
We want keys combined with underscore and values preserved.
Step 2: Check which code combines keys properly
nested = {a: {b: 1}} flat = {} nested.each { |k,v| v.each { |k2,v2| flat["#{k}_#{k2}"] = v2 } } iterates nested hashes and creates combined keys correctly.
Final Answer:
nested = {a: {b: 1}}\nflat = {}\nnested.each { |k,v| v.each { |k2,v2| flat["#{k}_#{k2}"] = v2 } } -> Option B
Quick Check:
Nested each loops combine keys with underscores [OK]

Quick Trick: Use nested each loops to flatten hashes with combined keys [OK]

Common Mistakes:

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