遍历哈希数组并添加到特定哈希值的值

Question

If you have an array of hashes such as:

t = [{'pies' => 1}, {'burgers' => 1}, {'chips' => 1}]

what would be an efficient and readable way to add 1 to the value of a hash that has a particular key such as 'pies' ?

Answer 1

Here's one way to increment the value(s) of an array's hashes based on a desired key:

t = [{ 'pies' => 1 }, { 'burgers' => 1 }, { 'chips' => 1 }]

t.each { |hash| hash['pies'] += 1 if hash.key?('pies') }
# => [{"pies"=>2}, {"burgers"=>1}, {"chips"=>1}]

Hope this helps!

Answer 2

If you know there's only one hash that could take the key 'pies' then you can use find and increase the value it has, like:

array = [{ 'pies' => 1 }, { 'burgers' => 1 }, { 'chips' => 1 }]
pies_hash = array.find { |hash| hash['pies'] }
pies_hash['pies'] += 1
p array
# [{"pies"=>2}, {"burgers"=>1}, {"chips"=>1}]

Enumerable#find will try to find the element that satisfies the block and stops the iteration when it returns true.

Answer 3

You're using the wrong data structure. I recommend using a Hash.

Each item on your menu can only have one count (or sale), that is each item is unique. This can be modelled with a hash with unique keys (the items) and their corresponding values (the counts).

t = {'pies' => 1, 'burgers' => 1, 'chips' => 1}

Then we can access keys and add to the count:

t['pies'] += 1
t #=> t = {'pies' => 2, 'burgers' => 1, 'chips' => 1}