class Hash(K, V)

• Hash(K, V)
• Reference
• Object

Overview

A Hash represents a collection of key-value mappings, similar to a dictionary.

Main operations are storing a key-value mapping (#[]=) and querying the value associated to a key (#[]). Key-value mappings can also be deleted (#delete). Keys are unique within a hash. When adding a key-value mapping with a key that is already in use, the old value will be forgotten.

# Create a new Hash for mapping String to Int32
hash = Hash(String, Int32).new
hash["one"] = 1
hash["two"] = 2
hash["one"] # => 1

Hash literals can also be used to create a Hash:

{"one" => 1, "two" => 2}

Implementation is based on an open hash table. Two objects refer to the same hash key when their hash value (Object#hash) is identical and both objects are equal to each other (Object#==).

Enumeration follows the order that the corresponding keys were inserted.

NOTE When using mutable data types as keys, changing the value of a key after it was inserted into the Hash may lead to undefined behaviour. This can be restored by re-indexing the hash with #rehash.

Included Modules

• Collection(K, V)
• Digable(K)
• Enumerable({K, V})
• Iterable({K, V})

Defined in:

Instance Method Summary

• #each_pair(&) : Nil

  Must yield this structure's key, value or index, element pairs.

• #each_pair : Iterator(Tuple(K, V))

  Provides an Iterator for each pair in self.

• #traverse(*prefix : *T, &) : Nil forall T

  Traverse the structure depth first yielding a tuple of the path through the structure and the leaf value for every element to the passed block.

• #traverse(*prefix : *T) : Iterator forall T

  Provide an iterator that may be used to traverse a nested structure.

Instance Method Detail