Dig method for nested access in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of dig with nested hashes

What is the output of this Ruby code using dig on nested hashes?

Ruby

data = {a: {b: {c: 42}}}
result = data.dig(:a, :b, :c)
puts result

A 42

B nil

C Error: NoMethodError

D 0

💡 Hint

Think about how dig accesses nested keys safely.

The dig method safely navigates nested hashes and returns the value at the deepest key if it exists. Here, :a, :b, and :c keys exist, so it returns 42.

❓ Predict Output

intermediate

Result of dig when key is missing

What does this Ruby code print when using dig with a missing key?

Ruby

data = {x: {y: 10}}
result = data.dig(:x, :z)
puts result.nil? ? 'nil' : result

A nil

B 10

C Error: KeyError

D false

💡 Hint

dig returns nil if any key in the chain is missing.

Since :z key does not exist inside :x, dig returns nil instead of raising an error.

🔧 Debug

advanced

Why does this dig call raise an error?

This Ruby code raises an error. What is the cause?

Ruby

data = {a: {b: nil}}
result = data.dig(:a, :b, :c)
puts result

A SyntaxError due to wrong dig usage

B KeyError because :c is missing

C Returns nil safely

D NoMethodError because dig tries to call :c on nil

💡 Hint

Consider what happens when dig encounters a nil value before the last key.

dig calls the next key on the value of :b, which is nil. Calling dig on nil causes NoMethodError.

🧠 Conceptual

advanced

Understanding dig with arrays and hashes

Given this Ruby data structure, what does data.dig(:users, 1, :name) return?

Ruby

data = {users: [{name: 'Alice'}, {name: 'Bob'}, {name: 'Carol'}]}

A "Alice"

B "Bob"

C nil

D Error: TypeError

💡 Hint

Remember dig can access array elements by index.

dig accesses :users key (an array), then index 1 (second element), then :name key, which is "Bob".

❓ Predict Output

expert

Output of dig with mixed nested structures and nil

What is the output of this Ruby code using dig on mixed nested hashes and arrays with nil values?

Ruby

data = {a: [{b: 1}, nil, {b: 3}]}
result = data.dig(:a, 1, :b)
puts result.nil? ? 'nil' : result

A nil

B 3

C Error: NoMethodError

D 1

💡 Hint

Check what happens when dig tries to access a key on a nil element inside an array.

The second element in :a array is nil, so dig tries to call dig(:b) on nil, which raises NoMethodError.