hash_map_hash
The hash_map_hash is a parser that transforms data structures (converted to
hashes) by using other hashes as maps.
It can be used to transform JSON, XML, or anything that can be converted
to Hash.
With this gem, it is possible to store multiple parser configurations (mappings) in files or in a database, and avoid writing a new parser for every new data format.
It can transform plain data structures, but is specifically designed to work with complex nested data structures. The resulting hash is always flat.
Installation
gem install hash_map_hash
This gem has no runtime dependencies.
Examples
Plain data structures
data = {
'Items' => 10,
'Total' => 123.0
}
mapping = {
amount: 'Items',
summ: 'Total'
}
HashMapHash.new(mapping).map(data) # { amount: 10, summ: 123.0 }Nested data structures
data = { 'Contractors' =>
{ 'Contractor' =>
[
{
'Value' => 'FirstAid, Moscow',
'Role' => 'Payer'
},
{
'Value' => '84266',
'OfficialName' => 'FirstAid, Moscow (442, Glow st)',
'Role' => 'Receiver'
}
]
},
'Items' => {
'NumberOfPositions' => 10
},
'Total' => 123.45
}
mapping = {
payer: ['Contractors', 'Contractor', %w(Role Payer), 'Value'],
receiver: ['Contractors', 'Contractor', %w(Role Receiver), 'Value'],
amount: ['Items', 'NumberOfPositions'],
summ: 'Total'
}
HashMapHash.new(mapping).map(data)
# {
# payer: 'FirstAid, Moscow',
# receiver: '84266',
# amount: 10,
# summ: 123.45
# }Note about mapping: each array element represents one level of a data hash. When element itself is an array, it is used for filtering a corresponding level of input hash, which in this case is also an array.
Nested properties
In the nested data example, two filters were applied under 'Contractors' and 'Contractor' keys. This duplication is not a big problem, even for dozens of such filters, but you can make them more DRY if you want by using nested properties.
# data is the same as in the nested data example
data = { 'Contractors' =>
{ 'Contractor' =>
[
{
'Value' => 'FirstAid, Moscow',
'Role' => 'Payer'
},
{
'Value' => '84266',
'OfficialName' => 'FirstAid, Moscow (442, Glow st)',
'Role' => 'Receiver'
}
]
},
'Items' => {
'NumberOfPositions' => 10
},
'Total' => 123.45
}
# initial maping, before adding nested properties
mapping = {
amount: ['Items', 'NumberOfPositions'],
summ: 'Total'
}
nested_properties = {
prefix: %w(Contractors Contractor),
filter_key: 'Role',
value_key: 'Value',
keys: {
payer: 'Payer',
receiver: 'Receiver'
}
}
mapper = HashMapHash.new(mapping)
mapper.add_nested_properties nested_properties
# Here is the new mapping.
# Now it is the same as in the nested data example.
mapper.mapping
# {
# payer: ['Contractors', 'Contractor', %w(Role Payer), 'Value'],
# receiver: ['Contractors', 'Contractor', %w(Role Receiver), 'Value'],
# amount: ['Items', 'NumberOfPositions'],
# summ: 'Total'
# }
# Same result as in the nested data example
mapper.map data
# {
# payer: 'FirstAid, Moscow',
# receiver: '84266',
# amount: 10,
# summ: 123.45
# }Backward transformation
For backward transformation use hash_template gem.
License
MIT.