Ruby Value of a Hash Key

How to find a hash key containing a matching value

You could use Enumerable#select:

clients.select{|key, hash| hash["client_id"] == "2180" }
#=> [["orange", {"client_id"=>"2180"}]]

Note that the result will be an array of all the matching values, where each is an array of the key and value.

Working with Hashes that have a default value

0 will be the fallback if you try to access a key in the hash that doesn't exist

For example:

count = Hash.new -> count['key'] => nil

vs

count = Hash.new(0) -> count['key'] => 0

Ruby: Creating a hash key and value from a variable in Ruby

If you want to populate a new hash with certain values, you can pass them to Hash::[]:

Hash["a", 100, "b", 200]             #=> {"a"=>100, "b"=>200}
Hash[ [ ["a", 100], ["b", 200] ] ]   #=> {"a"=>100, "b"=>200}
Hash["a" => 100, "b" => 200]         #=> {"a"=>100, "b"=>200}

So in your case:

Hash[id, 'foo']
Hash[[[id, 'foo']]]
Hash[id => 'foo']

The last syntax id => 'foo' can also be used with {}:

{ id => 'foo' }

Otherwise, if the hash already exists, use Hash#=[]:

h = {}
h[id] = 'foo'

Storing a function in the value for a key within a hash

You can use the send keyword

send h[step]

since you writing the method name directly in value part of the hash, the call is being made, but If you store the method names as a string and then if you call by send method as shown below, it would work.

def hi
  puts 'hi'
end

def hello
  puts 'hello'
end

h = {
    1 => 'hi',
    2 => 'hello',
}

send h[1]

Get key value pair of hash for the given key , in ruby

There is a method, Hash#assoc can do similar things. But it returns the key and value in an array, which you can easily change it into a hash.
And an alternative is use Hash#select, which does return a hash according to the block given.

h1 = { "fish" => "aquatic animal", "tiger" => "big cat" }
h1.assoc "fish"                       # ["fish", "aquatic animal"]
h1.select { |k,v| k == "fish" }       # {"fish"=>"aquatic animal"}

How to check if a specific key is present in a hash or not?

Hash's key? method tells you whether a given key is present or not.

session.key?("user")

Method to get value from a hash from array of keys in Ruby

[:font_size].inject(my_hash){|h, k| h.to_h[k]} #=> 10
[:boo, :name].inject(my_hash){|h, k| h.to_h[k]} #=> "blah"
[:boo, :foo].inject(my_hash){|h, k| h.to_h[k]} #=> nil

How to check if specific value is present in a hash?

Hash includes Enumerable, so you can use the many methods on that module to traverse the hash. It also has this handy method:

hash.has_value?(value_you_seek)

To find the key associated with that value:

hash.key(value_you_seek)

This API documentation for Ruby (1.9.2) should be helpful.

Ruby how to find each value in hash greater than x?

You can use:

months.select { |_month, days| days > 30 }    

This former gives you all results that fit the criteria (days > 30).

Here are the docs:

• select

Once you've got the values you need, you can then print them to the console (or output however you'd like), e.g.

long_months = months.select { |_month, days| days > 30 }
long_months.each { |month, days| puts "#{month} has #{days} days" }

---

All that being said, assigning to a value before printing the result means two loops, whereas this can be achieved in one using a simple each:

months.each do |month, days|
  puts("#{month} has #{days} days") if days > 30
end

That'll be more efficient as there's less churn involved :)

---

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