Transmogrifier is a tool that allows you to declaritively migrate a hash from one schema to another. It works by specifying a set of rules to apply to the hash and then running them in order.
engine = Transmogrifier::Engine.new
append = Transmogrifier::Rules::Append.new("", { "new_key" => "new_value" })
engine.add_rule(append)
input_hash = {"key" => "value"}
output_hash = engine.run(input_hash)
# output_hash => {"key" => "value", "new_key" => "new_value"}engine = Transmogrifier::Engine.new
update = Transmogrifier::Rules::Update.new("nested.nested_key", "updated-value")
engine.add_rule(update)
input_hash = {"key" => "value", "nested" => {"nested_key" => "nested_value"}}
output_hash = engine.run(input_hash)
# output_hash => {"key" => "value", "nested" => {"nested_key" => "updated-value"}}engine = Transmogrifier::Engine.new
copy = Transmogrifier::Rules::Copy.new("", "key", "nested.nested_key2")
engine.add_rule(copy)
input_hash = {"key" => "value", "nested" => {"nested_key" => "nested_value"}}
output_hash = engine.run(input_hash)
# output_hash => {"key" => "value", "nested" => {"nested_key" => "nested_value", "nested_key2" => "value"}}If the node to be copied does not exist, then this operation will no-op leaving the hash unchanged.
engine = Transmogrifier::Engine.new
delete = Transmogrifier::Rules::Delete.new("", "extra_key")
engine.add_rule(delete)
input_hash = {"key" => "value", "extra_key" => "some_value"}
output_hash = engine.run(input_hash)
# output_hash => {"key" => "value"}engine = Transmogrifier::Engine.new
move = Transmogrifier::Rules::Modify.new("key", "al", "og")
engine.add_rule(move)
input_hash = {"key" => "value"}
output_hash = engine.run(input_hash)
# output_hash => {"key" => "vogue"}engine = Transmogrifier::Engine.new
move = Transmogrifier::Rules::Move.new("", "key", "nested")
engine.add_rule(:move, "", "key", "nested")
input_hash = {"key" => "value", "nested" => {"nested_key" => "nested_value"}}
output_hash = engine.run(input_hash)
# output_hash => {"nested" => {"nested_key" => "nested_value", "key" => "value"}}Rules can be specified in ruby code, but they can also be loaded with an array.
rules = [
{
"type" => "append",
"selector" => "top",
"object" => {"some" => "attributes"},
},
{
"type" => "move",
"selector" => "top",
"from" => "key1",
"to" => "key2",
},
{
"type" => "delete",
"selector" => "top",
"name" => "key3",
},
]
engine = Transmogrifier::Engine.from_rules_array(rules)
input_hash = {
"top" => {
"key1" => "value1",
"key3" => "value2",
},
}
output_hash = engine.run(input_hash)
# output_hash =>
# {
# "top" => {
# "some" => "attributes",
# "key2" => "value1",
# },
# }Selectors are a string of hash keys seperated by dots that tell the Engine where to apply a given rule. For example, given the following structure:
{
"key" => "value",
"nested" => {
"second_level" => {
"deep" => "buried_value",
},
},
}the selector nested.second_level.deep will apply to buried_value. Rules can also be applied to hashes inside of an array. Given the structure:
{
"key" => "value",
"array" => [
{"name" => "not me"},
{"name" => "this one!"},
],
}the hash with the name this one! can be operated on with array.[name=this one!] or array.[name!=not me]. Arrays can also wildcard match all children. For example to match both hashes in the array above, use the selector array.[].
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