class Hash(K, V)

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

Defined in:

nason/any.cr
nason/to_json.cr

Constructors

Instance Method Summary

Instance methods inherited from class Reference

==(other : NASON::Any) ==

Instance methods inherited from class Object

===(other : NASON::Any) ===, nil_or_null? nil_or_null?, not_null! not_null!, null? null?, to_nason(io : IO) : Nil
to_nason : String to_nason, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json

Class methods inherited from class Object

from_nason(string_or_io, root : String)
from_nason(string_or_io) from_nason

Constructor Detail

def self.new(pull : NASON::PullParser) #

Reads a Hash from the given pull parser.

Keys are read by invoking from_json_object_key? on this hash's key type (K), which must return a value of type K or nil. If nil is returned a NASON::ParseException is raised.

Values are parsed using the regular .new(pull : NASON::PullParser) method.


[View source]

Instance Method Detail

def ==(other : NASON::Any) #

[View source]
def to_nason(json : NASON::Builder) : Nil #

Serializes this Hash into NASON.

Keys are serialized by invoking to_json_object_key on them. Values are serialized with the usual #to_nason(json : NASON::Builder) method.


[View source]