45 lines
1.6 KiB
Markdown
45 lines
1.6 KiB
Markdown
---
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title: Ruby Hashes
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---
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## Ruby Hashes
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A hash is a collection of keys and values. It is similar to what is commonly called a dictionary in other languages. In Ruby, a hash is similar to an <a href='https://raw.githubusercontent.com/freeCodeCamp/guides/master/src/pages/ruby/ruby-arrays/index.md' target='_blank' rel='nofollow'>array</a>, but rather than simply storing a value it stores a key, value pair.
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```ruby
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array = ["value"]
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hash = { "key" => "value" }
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```
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There are a couple of different ways to create a new hash:
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```ruby
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hash1 = {a: 100, b: "200"}
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hash2 = Hash.new
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hash3 = Hash.new(0) # with default value set to 0
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```
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A programmer can then access a hash value using its key, rather than the index.
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```ruby
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array[0] # => "value"
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hash["key"] # => "value"
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```
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In this way, a hash acts more like a dictionary where you can look up a value by its key.
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```ruby
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dictionary = { "Aardvark" => "a large, nocturnal, burrowing mammal",
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"Zyzzyva" => "a genus of tropical weevils" }
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dictionary["Aardvark"] # => "a large, nocturnal, burrowing mammal"
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dictionary["Zyzzyva"] # => "a genus of tropical weevils"
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```
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You can also create a hash using [symbols](#) as keys.
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```ruby
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hash = { :symbol => "value" }
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hash[:symbol] # => "value"
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```
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In addition, if all of your keys are [symbols](#), you can write your hash in this alternate format, but you would access it in the same manner:
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```ruby
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hash = { symbol: "value" }
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hash[:symbol] # => "value"
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```
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#### More Information:
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<a href='https://ruby-doc.org/core-2.4.2/Hash.html' target='_blank' rel='nofollow'>Ruby hash documentation</a>
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