Merge and update methods in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the merge method do in Ruby hashes?

It combines two hashes into a new hash. If keys overlap, the values from the second hash overwrite those from the first. The original hashes stay unchanged.

beginner

How does merge! differ from merge in Ruby?

merge! updates the original hash in place by adding or replacing keys and values from another hash, while merge returns a new hash without changing the original.

beginner

What happens if two hashes have the same key when using merge?

The value from the second hash replaces the value from the first hash for that key in the resulting hash.

beginner

Can you provide a simple example of using merge in Ruby?

Yes! For example:<br>

h1 = {a: 1, b: 2}
h2 = {b: 3, c: 4}
h3 = h1.merge(h2)
# h3 is {:a=>1, :b=>3, :c=>4}

intermediate

What is the return value of merge!?

merge! returns the updated original hash after merging the other hash into it.

What does hash1.merge(hash2) do in Ruby?

A Returns nil

B Updates hash1 in place with hash2's keys and values

C Deletes keys from hash1 that are in hash2

D Returns a new hash combining both, with hash2's values overwriting duplicates

The merge method returns a new hash combining both hashes, with values from the second hash overwriting duplicates.

Which method modifies the original hash in Ruby?

A merge!

B merge

C dup

D select

merge! modifies the original hash by merging another hash into it.

If h1 = {x: 1} and h2 = {x: 2}, what is h1.merge(h2)?

A {x: 2}

B {x: 1, x: 2}

C {x: 1}

D Error

The value for key :x from h2 overwrites the one from h1 in the merged hash.

What does merge! return after execution?

A A new hash

B The original hash updated

C An array of keys

D nil

merge! returns the original hash after it has been updated.

Which of these is true about merge and merge!?

A <code>merge</code> changes the original hash, <code>merge!</code> does not

B Both change the original hash

C <code>merge</code> returns a new hash, <code>merge!</code> changes the original hash

D Neither changes the original hash

merge returns a new hash without changing the original, while merge! updates the original hash.

Explain how the merge and merge! methods work in Ruby hashes.

Think about whether the original hash changes or not.

Describe a situation where you would prefer to use merge over merge!.

Consider if you want to keep your original data intact.