StructTrans
by Lin Jen-Shin (godfat)
LINKS:
DESCRIPTION:
Transform a struct with a schema to a hash, other struct, or more.
WHY?
We need an easy way to define how we want to expose data to the external.
REQUIREMENTS:
- Tested with MRI (official CRuby) and JRuby.
INSTALLATION:
gem install struct_trans
SYNOPSIS:
Here's an example to transform a struct-like object, i.e. 'nnf'
into a hash
with a specific schema defined by a hash containing an array containing
another hash and a symbol.
p StructTrans.trans_hash(
'nnf',
:inspect, {:reverse => [{:capitalize => :swapcase}, :upcase]})
# {:inspect => '"nnf"', :reverse => {:capitalize => {:swapcase => 'fNN'}, :upcase => 'FNN'}}
We could also transform the same struct (i.e. 'nnf'
) into an open struct
rather than a hash if you prefer.
require 'struct_trans/ostruct'
o = StructTrans.trans_ostruct(
'nnf',
:upcase, {:reverse => [{:capitalize => :swapcase}, :upcase]})
p o.upcase # 'NNF'
p o.reverse.capitalize.swapcase # 'fNN'
p o.reverse.upcase # 'FNN'
Demonstrations
Consider that you have a User
model and Message
model.
You want to expose them to the external world.
User = Struct.new(:id, :legacy_name, :messages)
Message = Struct.new(:content, :sender)
require 'forwardable'
module Trans
def trans_hash *extra
StructTrans.trans_hash(self, *self.class.schema(*extra))
end
end
module Entity
def entity *extra
{method(:new) => schema(*extra)}
end
end
UserEntity = Struct.new(:user) do
extend Forwardable
def_delegator :user, :legacy_name, :name
def_delegators :user, :id, :messages
include Trans
extend Entity
def self.schema *extra
[:name] + extra
end
end
MessageEntity = Struct.new(:message) do
extend Forwardable
def_delegators :message, :content, :sender
include Trans
extend Entity
def self.schema *extra
[:content, {:sender => UserEntity.entity(:id)}] + extra
end
end
user = User.new(0, 'Fungi')
messages = [Message.new('nnf', user), Message.new('mmf', user)]
user.messages = messages
p UserEntity.new(user).trans_hash(:id, [:messages] => MessageEntity.entity)
# {:id => 0, :name => 'Fungi', :messages => [{:content => 'nnf', :sender => {:id => 0, :name => 'Fungi'}}, {:content => 'mmf', :sender => {:id => 0, :name => 'Fungi'}}]}
CONTRIBUTORS:
- Lin Jen-Shin (@godfat)
LICENSE:
Apache License 2.0 (Apache-2.0)
Copyright (c) 2016-2019, Lin Jen-Shin (godfat)
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.