Servicer
Simple Service Object builder.
Installation
gem install servicer
Basic usage
Servicer provides base class for building services, and set of additional layers for changing behaviour.
Simplest use case is building Command Object for API:
class CreateUser < ::Servicer::Base
def call(current_user, params)
User.create(params)
end
end
CreateUser.call(current_user, params) #=> new User
In that form no layers are applied, so input will not be changed in any way. Servicer is proxying class call
method,
building new instance and calling call
with the same params as provided (unless modified by layers).
Layers
Layers are modifying how given service object behave. They can validate input, change params, and raise errors. Simplest call would look like this:
class CreateUser < ::Servicer::Base
layer :require_user
def call(current_user, params)
User.create(params)
end
end
Multiple layers can be applied and they will be executed in order of mentioning them. Some of them will require additional parameters, documentation can be found below.
RequireUser
This layer is raising Servicer::AuthorizationError
is current user is not provided. This layer is not accepting
any options.
class CreateUser < ::Servicer::Base
layer :require_user
def call(current_user, params)
User.create(params)
end
end
CreateUser.call(nil, params) #=> raises Servicer::AuthorizationError
SetDefaultParams
This layer is merging received params with default values provided using deep merge (nested hash values will be merged). Values from provided params always take precedence over default values.
class CreateUser < ::Servicer::Base
layer :set_default_values, {
role: 'user'
}
def call(current_user, params)
User.create(params)
end
end
CreateUser.call(nil, {}) #=> user.role == 'user'
CreateUser.call(nil, { role: 'admin' }) #=> user.role == 'admin'
ValidateParams
This layer is validating params provided, raising Servicer::ParamsError
if validation fails, and filtering any param
that was not validated. It's using dry-validation under the hood, and you need
to include it in your Gemfile.
Please bear in mind that it's used for validating input, and not for checking user permissions.
class CreateUser < ::Servicer::Base
layer :validate_params do
required(:role).filled(:str?)
optional(:age).filled(:int?, gt?: 17)
end
def call(current_user, params)
User.create(params)
end
end
CreateUser.call(nil, {}) #=> raises Servicer::ParamsError
CreateUser.call(nil, { role: 1 }) #=> raises Servicer::ParamsError
CreateUser.call(nil, { role: 'admin' }) #=> user.role == 'admin'
CreateUser.call(nil, { role: 'admin', age: 17 }) #=> raises Servicer::ParamsError
CreateUser.call(nil, { role: 'admin', age: 18 }) #=> user.role == 'admin', user.age == 18
Combining layers
Multiple layers can be used together in order to provide final service:
class CreateUser < ::Servicer::Base
layer :require_user
layer :validate_params do
optional(:role).filled(:str?)
required(:age).filled(:int?, gt?: 17)
end
layer :set_default_values, {
role: 'user'
}
def call(current_user, params)
User.create(params)
end
end
class ListUsers < ::Servicer::Base
layer :validate_params do
optional(:role).filled(:str?)
optional(:limit).filled(:int?, gt?: 0, lt?: 1000)
optional(:offset).filled(:int?)
end
layer :set_default_values, {
limit: 10,
offset: 0
}
def call(current_user, params)
limit = params.delete(:limit)
offset = params.delete(:offset)
User.where(params).limit(limit).offset(offset)
end
end
License
(The MIT License)
Copyright © 2018 Bernard Potocki
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.