How to add new item to hash

问题:

I'm new to Ruby and don't know how to add new item to already existing hash. For example, first I construct hash:

hash = {item1: 1}

after that a want to add item2 so after this I have hash like this:

{item1: 1, item2: 2}

I don't know what method to do on hash, could someone help me?

回答1:

Create the hash:

hash = {:item1 => 1}

Add a new item to it:

hash[:item2] = 2

回答2:

If you want to add new items from another hash - use merge method:

hash = {:item1 => 1}
another_hash = {:item2 => 2, :item3 => 3}
hash.merge(another_hash) # {:item1=>1, :item2=>2, :item3=>3}

In your specific case it could be:

hash = {:item1 => 1}
hash.merge({:item2 => 2}) # {:item1=>1, :item2=>2}

but it's not wise to use it when you should to add just one element more.

Pay attention that merge will replace the values with the existing keys:

hash = {:item1 => 1}
hash.merge({:item1 => 2}) # {:item1=>2}

exactly like hash[:item1] = 2

Also you should pay attention that merge method (of course) doesn't effect the original value of hash variable - it returns a new merged hash. If you want to replace the value of the hash variable then use merge! instead:

hash = {:item1 => 1}
hash.merge!({:item2 => 2})
# now hash == {:item1=>1, :item2=>2}

回答3:

It's as simple as:

irb(main):001:0> hash = {:item1 => 1}
=> {:item1=>1}
irb(main):002:0> hash[:item2] = 2
=> 2
irb(main):003:0> hash
=> {:item1=>1, :item2=>2}

回答4:

hash.store(key, value) - Stores a key-value pair in hash.

Example:

hash   #=> {"a"=>9, "b"=>200, "c"=>4}
hash.store("d", 42) #=> 42
hash   #=> {"a"=>9, "b"=>200, "c"=>4, "d"=>42}

Documentation

回答5:

hash[key]=value Associates the value given by value with the key given by key.

hash[:newKey] = "newValue"

From Ruby documentation: http://www.tutorialspoint.com/ruby/ruby_hashes.htm

回答6:

hash_items = {:item => 1}
puts hash_items 
#hash_items will give you {:item => 1}

hash_items.merge!({:item => 2})
puts hash_items 
#hash_items will give you {:item => 1, :item => 2}

hash_items.merge({:item => 2})
puts hash_items 
#hash_items will give you {:item => 1, :item => 2}, but the original variable will be the same old one. 

回答7:

Create hash as:

h = Hash.new
=> {}

Now insert into hash as:

h = Hash["one" => 1]